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History
Philodendrons are known to have been collected from the wild as early as 1644 by Georg Marcgraf, but the first partly successful scientific attempt to collect and classify the genus was done by Charles Plumier. Plumier collected approximately six species from the islands of Martinique, Hispaniola, and St. Thomas. Since then, many exploration attempts have been made to collect new species by others. These include those by N.J. Jacquin who collected new species in the West Indies, Colombia, and Venezuela. At this time in history, the names of the philodendrons they were discovering were being published with the genus name Arum, since most aroids were considered to belong to this same genus. The genus Philodendron had not yet been created. Throughout the late 17th, 18th century, and early 19th centuries, many plants were removed from the genus Arum and placed into newly created genera in an attempt to improve the classification. Heinrich Wilhelm Schott addressed the problem of providing improved taxonomy and created the genus Philodendron and described it in 1829. The genus was first spelled as 'Philodendrum', but in 1832, Schott published a system for classifying plants in the family Araceae titled Meletemata Botanica in which he provided a method of classifying philodendrons based on flowering characteristics. In 1856, Schott published a revision of his previous work titled Synopsis aroidearum, and then published his final work Prodromus Systematis Aroidearum in 1860, in which he provided even more details about the classification of Philodendron and described 135 species.
Modern classification
Philodendron are usually extremely distinctive and not usually confused with other genera, although a few exceptions in the genera Anthurium and Homalomena resemble Philodendron.
The genus Philodendron has been subdivided into three subgenera: Meconostigma, Pteromischum, and Philodendron. In 2018, it was proposed that Philodendron subg. Meconostigma be recognized as a separate genus, Thaumatophyllum. | Philodendron | Wikipedia | 439 | 576200 | https://en.wikipedia.org/wiki/Philodendron | Biology and health sciences | Monocots | null |
The genus Philodendron can also be subdivided into several sections and subsections. Section Baursia, section Philopsammos, section Philodendron (subsections Achyropodium, Canniphyllium, Macrolonchium, Philodendron, Platypodium, Psoropodium and Solenosterigma), section Calostigma (subsections Bulaoana, Eucardium, Glossophyllum, Macrobelium and Oligocarpidium), section Tritomophyllum, section Schizophyllum, section Polytomium, section Macrogynium and section Camptogynium.
Typically, the inflorescence is of great importance in determining the species of a given philodendron, since it tends to be less variable than the leaves. The genus Philodendron could be classified further by means of differentiating them based on the pattern of thermogenesis observed, although this is not currently used.
Selected species | Philodendron | Wikipedia | 209 | 576200 | https://en.wikipedia.org/wiki/Philodendron | Biology and health sciences | Monocots | null |
Philodendron acutatum Schott
Philodendron alliodorum Croat & Grayum
Philodendron appendiculatum Nadruz & Mayo
Philodendron auriculatum Standl. & L. O. Williams
Philodendron balaoanum Engl.
Philodendron bipennifolium Schott
Philodendron carinatum E.G.Gonç.
Philodendron chimboanum Engl.
Philodendron consanguineum Schott - rascagarganta
Philodendron cordatum (Vell.) Kunth
Philodendron crassinervium Lindl.
Philodendron cruentospathum Madison
Philodendron davidsonii Croat
Philodendron devansayeanum L. Linden
Philodendron domesticum G. S. Bunting
Philodendron duckei Croat & Grayum
Philodendron ensifolium Croat & Grayum
Philodendron erubescens K. Koch & Augustin
Philodendron eximium Schott
Philodendron fragrantissimum (Hook.) G. Don in Sweet
Philodendron ferrugineum Croat
Philodendron giganteum Schott - giant philodendron
Philodendron gigas Croat
Philodendron gloriosum André
Philodendron gualeanum Engl.
Philodendron hastatum K. Koch & Sello - silver philodendron, also known incorrectly as Philodendron glaucophyllum
Philodendron hederaceum (Jacq.) Schott - vilevine, heartleaf philodendron, velvet-leaved philodendron
Philodendron herbaceum Croat & Grayum
Philodendron hooveri Croat & Grayum
Philodendron imbe Schott ex Endl. - philodendron
Philodendron jacquinii Schott
Philodendron lacerum (Jacq.) Schott
Philodendron lingulatum (L.) K. Koch - treelover
Philodendron mamei André
Philodendron marginatum Urban - Puerto Rico philodendron
Philodendron martianum Engl.- also known incorrectly as Philodendron cannifolium
Philodendron mayoii Symon Mayo | Philodendron | Wikipedia | 512 | 576200 | https://en.wikipedia.org/wiki/Philodendron | Biology and health sciences | Monocots | null |
Philodendron maximum K. Krause
Philodendron melanochrysum Linden & André
Philodendron microstictum Standl. & L. O. Williams
Philodendron musifolium Engl.
Philodendron nanegalense Engl.
Philodendron opacum Croat & Grayum
Philodendron ornatum Schott
Philodendron pachycaule K. Krause
Philodendron panduriforme (Kunth) Kunth
Philodendron pedatum (Hook.) Kunth
Philodendron pinnatifidum (Jacq.) Schott
Philodendron pogonocaule Madison
Philodendron pterotum K.Koch & Augustin
Philodendron quitense Engl.
Philodendron radiatum Schott
Philodendron recurvifolium Schott
Philodendron renauxii Reitz
Philodendron riparium Engl.
Philodendron robustum Schott
Philodendron rugosum Bogner & G.S.Bunting
Philodendron sagittifolium Liebm.
Philodendron santa leopoldina Liebm.
Philodendron sphalerum Schott
Philodendron squamiferum Poepp.
Philodendron standleyi Grayum
Philodendron tatei Krause
Philodendron tripartitum (Jacq.) Schott
Philodendron validinervium Engl.
Philodendron ventricosum Madison
Philodendron verrucosum L. Mathieu ex Schott
Philodendron victoriae G.S. Bunting
Philodendron warszewiczii K. Koch & C. D. Bouché
Philodendron wendlandii Schott | Philodendron | Wikipedia | 393 | 576200 | https://en.wikipedia.org/wiki/Philodendron | Biology and health sciences | Monocots | null |
Evolution
Philodendron diverged from Adelonema and diversified during the late Oligocene, 25 million years ago, in the New World.
Distribution and habitat
Philodendron species can be found in many diverse habitats in the tropical Americas and the West Indies. Most occur in humid tropical forests, but can also be found in swamps and on river banks, roadsides and rock outcrops. They are also found throughout the diverse range of elevations from sea level to over 2000 m above sea level. Species of this genus are often found clambering over other plants, or climbing the trunks of trees with the aid of aerial roots. Philodendrons usually distinguish themselves in their environment by their large numbers compared to other plants, making them a highly noticeable component of the ecosystems in which they are found. They are found in great numbers in road clearings.
Philodendrons can also be found in Australia, some Pacific islands, Africa and Asia, although they are not indigenous and were introduced or accidentally escaped.
Ecology
The leaves of philodendrons are also known to be eaten by Venezuelan red howler monkeys, making up 3.1% of all the leaves they eat.
The resins produced during the flowering of Monstera and Philodendron are known to be used by Trigona bees in the construction of their nests. | Philodendron | Wikipedia | 273 | 576200 | https://en.wikipedia.org/wiki/Philodendron | Biology and health sciences | Monocots | null |
The spathe provides a safe breeding area for beetles. As such, male beetles are often followed there by female beetles. The philodendrons benefit from this symbiotic relationship because the males will eventually leave the spathe covered in pollen and repeat the process at another philodendron, pollinating it in the process. Females that see a male beetle headed for a philodendron flower know he does so with intention of mating, and females which are sexually receptive and need to mate know that they can find males if they follow the pheromones produced by the philodendron flowers. As a result, the male beetles benefit from this relationship with the philodendrons because they do not have to produce pheromones to attract females. Additionally, male beetles benefit because they are ensured of mating with only sexually receptive females. Pheromones produced by the philodendrons may be similar to those produced by female beetles when they wish to attract males to mate. Also, the pheromones have a sweet, fruity smell in many species and no noticeable smell for others. Additionally, the beetles consume pollen from the fertile male flowers throughout the night, in addition to the sterile male flowers which are rich in lipids.
Typically, five to 12 beetles will be within the spathe throughout the night. Rarely, cases of 200 beetles at a time have been observed and almost always the beetles are of the same species. Another feature of this symbiotic relationship, less well understood, is the series of events in which the spadix begins to heat up prior to the spathe opening up for the beetles. This process is known as thermogenesis. By the time the spathe is open and the beetles have arrived, the spadix is usually quite hot; up to around 46 °C in some species, but usually around 35 °C. The thermogenesis coincides with the arrival of the beetles and appears to increase their presence. The maximum temperature reached by the spadix remains about 20 °C higher than the outside ambient temperature. The time dependence of the temperature can vary from species to species. In some species, the temperature of the spadix will peak on the arrival of the beetles, then decrease, and finally increase reaching a maximum once again when the philodendron is ready for the beetles to leave. Other species, though, only show a maximum temperature on the arrival of the beetles, which remains roughly constant for about a day, and then steadily decreases. | Philodendron | Wikipedia | 512 | 576200 | https://en.wikipedia.org/wiki/Philodendron | Biology and health sciences | Monocots | null |
As the beetles home in on the inflorescence, they first move in a zig-zag pattern until they get reasonably close, when they switch to a straight-line path. The beetles may use scent to find the inflorescence when they are far away, but once within range, they find it by means of the infrared radiation, accounting for the two types of paths the beetles follow.
Cultivation
Growing
Philodendrons can be grown outdoors in mild climates in shady spots. They thrive in moist soils with high organic matter. In milder climates, they can be grown in pots of soil or in the case of Philodendron oxycardium in containers of water. Indoor plants thrive at temperatures between 15 and 18 °C and can survive at lower light levels than other house plants. Although philodendrons can survive in dark places, they much prefer bright lights. Wiping the leaves off with water will remove any dust and insects. Plants in pots with good root systems will benefit from a weak fertilizer solution every other week.
Propagation
New plants can be grown by taking stem cuttings with at least two joints. Cuttings then can be rooted in pots of sand and peat moss mixtures. These pots are placed in greenhouses with bottom heat of 21–24 °C. During the rooting, cuttings should be kept out of direct sunlight. Once rooted, the plants can be transplanted to larger pots or directly outside in milder climates. Stem cuttings, particularly from trailing varieties, can be rooted in water. In four to five weeks, the plant should develop roots and can be transferred to pots. Philodendrons can also propagate through air layering which is a more advanced method of propagation that involves creating a new plant on the stem of an existing plant. | Philodendron | Wikipedia | 363 | 576200 | https://en.wikipedia.org/wiki/Philodendron | Biology and health sciences | Monocots | null |
Hybridizing philodendrons is quite easy if flowering plants are available, because they have very few barriers to prevent hybridization. However, some aspects of making crosses can make philodendron hybridization more difficult. Philodendrons often flower at different times and the time when the spathe opens up varies from plant to plant. The pollen and the inflorescence both have short lives, which means a large collection of philodendrons is necessary if crossbreeding is to be done successfully. The pollen life can be extended to a few weeks by storing it in film canisters in a refrigerator. Artificial pollination is usually achieved by first mixing the pollen with water. A window is then cut into the spathe and the water-pollen mixture is rubbed on the fertile female flowers. The entire spathe is then covered in a plastic bag so the water–pollen mixture does not dry out; the bag is removed a few days later. If the inflorescence has not been fertilized, it will fall off, usually within a few weeks. | Philodendron | Wikipedia | 215 | 576200 | https://en.wikipedia.org/wiki/Philodendron | Biology and health sciences | Monocots | null |
Toxicity
Philodendrons can contain as much as 0.7% of oxalates in the form of calcium oxalate crystals as raphides. The risk of death, if even possible, is extremely low if ingested by an average adult, although its consumption is generally considered unhealthy. In general, the calcium oxalate crystals have a very mild effect on humans, and large quantities have to be consumed for symptoms to even appear. Possible symptoms include increased salivation, a sensation of burning of the mouth, swelling of the tongue, stomatitis, dysphagia, an inability to speak, and edema. Cases of mild dermatitis due to contact with the leaves have also been reported, with symptoms including vesiculation and erythema. The chemical derivatives of alkenyl resorcinol are believed to be responsible for the dermatitis in some people. Contact with philodendron oils or fluids with the eyes have also been known to result in conjunctivitis. Fatal poisonings are extremely rare; one case of an infant eating small quantities of a philodendron resulting in hospitalization and death has been reported. This one case study, however, was found to be inconsistent with the findings from a second study. In this study, 127 cases of children ingesting philodendrons were studied, and they found only one child showed symptoms; a 10-month-old had minor upper lip swelling when he chewed on a philodendron leaf. The study also found the symptoms could subside without treatment and that previously reported cases of severe complications were exaggerated. | Philodendron | Wikipedia | 332 | 576200 | https://en.wikipedia.org/wiki/Philodendron | Biology and health sciences | Monocots | null |
In a 1961 study, 72 cases of cat poisonings were examined, of which 37 resulted in the death of the cat. The symptoms of the poisoned cats included excitability, spasms, seizures, kidney failure, and encephalitis. In a 1978 study, three cats (two adults and one kitten) were tube-fed a puréed leaf and water mixture of P. cordatum, then euthanized. A necropsy showed no signs or symptoms of acute poisoning or toxicity. Dosages of 2.8, 5.6, and 9.1 g/kg were used, the highest dose being much more than a house cat could consume. Earlier epidemiological studies (which did not necessarily invoke a purée-and-water feeding method) were suggested to be wrong based on the premise that many of the sick cats in those studies may have had conditions and merely consumed philodendrons in an attempt to alleviate their illnesses.
Some philodendrons are known to be toxic to mice and rats. In one study, 100 mg of P. cordatum leaves suspended in distilled water were fed to six mice. Three of the mice died. The same experiment was done with 100 mg of P. cordatum stems on three mice and none of them died. Leaves and flowers of P. sagittifolium were also orally administered in 100-mg doses to the mice. Three mice were used for each of the leaves and flowers; none of the mice died. A similar experiment was done on rats with the leaves and stems of P. cordatum, but instead of oral administration of the dose, it was injected intraperitoneally using 3 g of plant extract from either the leaves or stems. Six rats were injected with the leaf extract and five of them died. Eight rats were injected with the stem extract and two of them died.
Uses
Indigenous people from South America use the resin from bees' nests (made from the species) to make their blowguns air- and watertight.
Though they contain calcium oxalate crystals, the berries of some species are eaten by the locals. For example, the sweet white berries of Thaumatophyllum bipinnatifidum are known to be used. Additionally, the aerial roots are also used for rope in this particular species. | Philodendron | Wikipedia | 478 | 576200 | https://en.wikipedia.org/wiki/Philodendron | Biology and health sciences | Monocots | null |
Also, in the making of a particular recipe for curare by the Amazonian Taiwanos, the leaves and stems of an unknown philodendron species are used. The leaves and stems are mixed with the bark of Vochysia ferruginea and with some parts of a species in the genus Strychnos.
Yet another use of philodendrons is for catching fish. A tribe in the Colombian Amazon is known to use P. craspedodromum to add poison to the water, temporarily stunning the fish, which rise up to the surface, where they can be easily scooped up. To add the poison to the water, the leaves are cut into pieces and tied together to form bundles, which are allowed to ferment for a few days. The bundles are crushed and added to the water into which the poison will dissipate. Although the toxicity of P. craspedodromum is not fully known, active ingredients in the poisoning of the fish possibly are coumarins formed during the fermentation process.
Some philodendrons are also used for ceremonial purposes. Among the Kubeo tribe, native to Colombia, P. insigne is used by witch doctors to assuage ill patients. They use the juice of the spathe to stain their hands red, since many such tribes view the color red as a sign of power. | Philodendron | Wikipedia | 284 | 576200 | https://en.wikipedia.org/wiki/Philodendron | Biology and health sciences | Monocots | null |
The Clydesdale is a Scottish breed of draught horse. It takes its name from Clydesdale, a region of Scotland centred on the River Clyde.
The origins of the breed lie in the seventeenth century, when Flemish stallions were imported to Scotland and mated with local mares; in the nineteenth century, Shire blood was introduced. The first recorded use of the name "Clydesdale" for the breed was in 1826; the horses spread through much of Scotland and into northern England. After the breed society was formed in 1877, thousands of Clydesdales were exported to many countries of the world, particularly to Australia and New Zealand. In the early twentieth century numbers began to fall, both because many were taken for use in the First World War, and because of the increasing mechanisation of agriculture. By the 1970s, the Rare Breeds Survival Trust considered the breed vulnerable to extinction. Numbers have since increased slightly.
It is a large and powerful horse, although now not as heavy as in the past. It was traditionally used for draught power, both in farming and in road haulage. It is now principally a carriage horse. It may be ridden or driven in parades or processions. In the United States the Anheuser-Busch brewery uses a matched team of eight for publicity.
History
The Clydesdale horse takes its name from Clydesdale, the valley of the River Clyde. In the late seventeenth century, stallions of Friesian and Flemish stock from the Low Countries were imported to Scotland and bred to local mares. These included a black unnamed stallion imported from England by a John Paterson of Lochlyloch and an unnamed dark-brown stallion owned by the Duke of Hamilton.
Another prominent stallion was a coach horse stallion of unknown lineage named Blaze. Written pedigrees were kept of these foals beginning in the early nineteenth century, and in 1806, a filly, later known as "Lampits mare" after the farm name of her owner, was born that traced her lineage to the black stallion. This mare is listed in the ancestry of almost every Clydesdale living today. One of her foals was Thompson's Black Horse (known as Glancer), which was to have a significant influence on the Clydesdale breed. | Clydesdale horse | Wikipedia | 450 | 576517 | https://en.wikipedia.org/wiki/Clydesdale%20horse | Biology and health sciences | Horses | Animals |
The first recorded use of the name "Clydesdale" in reference to the breed was in 1826 at an exhibition in Glasgow. Another theory of their origin, that of them descending from Flemish horses brought to Scotland as early as the 15th century, was also promulgated in the late 18th century. However, even the author of that theory admitted that the common story of their ancestry is more likely.
A system of hiring stallions between districts existed in Scotland, with written records dating back to 1837. This programme consisted of local agriculture improvement societies holding breed shows to choose the best stallion, whose owner was then awarded a monetary prize. The owner was then required, in return for additional monies, to take the stallion throughout a designated area, breeding to the local mares. Through this system and by purchase, Clydesdale stallions were sent throughout Scotland and into northern England.
Through extensive crossbreeding with local mares, these stallions spread the Clydesdale type throughout the areas where they were placed, and by 1840, Scottish draught horses and the Clydesdale were one and the same. In 1877, the Clydesdale Horse Society of Scotland was formed, followed in 1879 by the American Clydesdale Association (later renamed the Clydesdale Breeders of the USA), which served both U.S. and Canadian breed enthusiasts. The first American stud book was published in 1882. In 1883, the short-lived Select Clydesdale Horse Society was founded to compete with the Clydesdale Horse Society. It was started by two breeders dedicated to improving the breed, who also were responsible in large part for the introduction of Shire blood into the Clydesdale.
Large numbers of Clydesdales were exported from Scotland in the late nineteenth and early twentieth centuries, with 1617 stallions leaving the country in 1911 alone. Between 1884 and 1945, export certificates were issued for 20,183 horses. These horses were exported to other countries in the British Empire, as well as North and South America, continental Europe, and Russia.
The First World War had the conscription of thousands of horses for the war effort, and after the war, breed numbers declined as farms became increasingly mechanised. This decline continued between the wars. Following the Second World War, the number of Clydesdale breeding stallions in England dropped from more than 200 in 1946 to 80 in 1949. By 1975, the Rare Breeds Survival Trust considered them vulnerable to extinction, meaning fewer than 900 breeding females remained in the UK. | Clydesdale horse | Wikipedia | 490 | 576517 | https://en.wikipedia.org/wiki/Clydesdale%20horse | Biology and health sciences | Horses | Animals |
Many of the horses exported from Scotland in the nineteenth and twentieth centuries went to Australia and New Zealand. In 1918, the Commonwealth Clydesdale Horse Society was formed as the association for the breed in Australia. Between 1906 and 1936, Clydesdales were bred so extensively in Australia that other draught breeds were almost unknown. By the late 1960s, it was noted that "Excellent Clydesdale horses are bred in Victoria and New Zealand; but, at least in the former place, it is considered advisable to keep up the type by frequent importations from England." Over 25,000 Clydesdales were registered in Australia between 1924 and 2008. The popularity of the Clydesdale led to it being called "the breed that built Australia".
Conservation status
In the 1990s, numbers began to rise. By 2005, the Rare Breeds Survival Trust had moved the breed to "at risk" status, meaning that there were fewer than 1,500 breeding females in the UK. By 2010 it had been moved back to "vulnerable".
In 2010, the worldwide Clydesdale horse population was estimated to be 5,000, with around 4,000 in the United States and Canada, 800 in the UK, and the rest in other countries, including Russia, Japan, Germany, and South Africa.. The same year, the Clydesdale was listed as "watch" by The Livestock Conservancy, meaning that fewer than 2500 horses were registered annually in the USA, and there were fewer than 10,000 worldwide. By 2024, the Clydesdale was listed as "threatened" (<1,000 annual US registrations and <5,000 global population). According to The Livestock Conservancy, "The North American population of Clydesdale horses had increased steadily for several decades, but a sharp decline began around 2010, prompted by the economic downturn that affected the entire equine market. Globally, the breed is well-known, but not common, with an estimated global population of fewer than 5,000 horses."
Inbreeding has also become an issue for the breed, and a 2013 study found that the Clydesdale had one of the highest inbreeding coefficients among all horse breeds.
Characteristics | Clydesdale horse | Wikipedia | 443 | 576517 | https://en.wikipedia.org/wiki/Clydesdale%20horse | Biology and health sciences | Horses | Animals |
The conformation of the Clydesdale has changed greatly throughout its history. In the 1920s and 1930s, it was a compact horse smaller than the Shire, Percheron, and Belgian Draught. Beginning in the 1940s, breeding animals were selected to produce taller horses that looked more impressive in parades and shows. Today, the Clydesdale stands high and weighs . Some mature males are larger, standing taller than 183 cm and weighing up to . The breed has a straight facial profile or a slight Roman nose, broad forehead, and wide muzzle.
It is well-muscled and strong, with an arched neck, high withers, and a sloped shoulder. Breed associations pay close attention to the quality of the hooves and legs, as well as the general movement. Their gaits are active, with clearly lifted hooves and a general impression of power and quality. Clydesdales are energetic, with a manner described by the Clydesdale Horse Society as a "gaiety of carriage and outlook".
Clydesdales are usually bay or brown in colour. Roans are common, and black, grey and chestnut also occur. Most have white markings, including white on the face, feet, and legs, and occasional white patches on the body (generally on the lower belly). They have extensive feathering on their lower legs. Cow hocks, where the hocks turn inward are a breed characteristic and not a fault.
Many buyers pay a premium for bay and black horses, especially those with four white legs and white facial markings. Specific colours are often preferred over other physical traits, and some buyers even choose horses with soundness problems if they have the desired colour and markings. Buyers do not favour Sabino-like horses, despite one draught-breed writer theorising that they are needed to keep the desired coat colours and texture. Breed associations, however, state that no colour is bad, and that horses with roaning and body spots are increasingly accepted.
Clydesdales have been identified to be at risk for chronic progressive lymphedema, a disease with clinical signs that include progressive swelling, hyperkeratosis, and fibrosis of distal limbs that is similar to chronic lymphedema in humans. Another health concern is a skin condition on the lower leg where feathering is heavy. Colloquially called "Clyde's itch", it is thought to be caused by a type of mange. Clydesdales are also known to develop sunburn on any pink (unpigmented) skin around their faces.
Uses | Clydesdale horse | Wikipedia | 509 | 576517 | https://en.wikipedia.org/wiki/Clydesdale%20horse | Biology and health sciences | Horses | Animals |
The Clydesdale was originally used for agriculture, hauling coal in Lanarkshire, and heavy hauling in Glasgow. Today, Clydesdales are still used for draught purposes, including agriculture, logging, and driving. They are also shown and ridden, as well as kept for pleasure. Clydesdales are known to be the popular breed choice with carriage services and parade horses because of their white, feathered legs.
Along with carriage horses, Clydesdales are also used as show horses. They are shown in lead line and harness classes at county and state fairs, as well as national exhibitions.
Some of the most famous members of the breed are the teams that make up the hitches of the Budweiser Clydesdales. The Budweiser Brewery first formed these teams at the end of Prohibition, and they have since become an international symbol of both the breed and the brand. The Budweiser breeding programme, with its strict standards of colour and conformation, have influenced the look of the breed in the United States to the point that many people believe that Clydesdales are always bay with white markings.
Influence on other breeds
In the second half of the 1800s, Clydesdale and Shire blood was added to the Irish Draught breed in an attempt to reinvigorate that declining breed. However, those efforts were not seen as successful, as Irish Draught breeders thought the Clydesdale blood made their horses coarser and prone to lower leg faults, such as tied-in below the knee.
The Australian Draught horse was created using European draft breeds, including the Clydesdale, imported in the late 1800s.
In the early 1900s it was considered profitable to breed Clydesdale stallions to Dales Pony mares to create a mid-sized draught horses for pulling commercial wagons and military artillery. Unfortunately, after just a few years, the Dales breed was two-thirds Clydesdale. They started a breed registry in 1916 to preserve the Dales, and by 1923 the Army was buying only Dales with no signs of carthorse blood. The modern Dales shows no signs of Clydesdale characteristics.
The Clydesdale contributed to the development of the Gypsy horse in Great Britain along with Friesian, Shire and Dale, although no written records were kept. | Clydesdale horse | Wikipedia | 448 | 576517 | https://en.wikipedia.org/wiki/Clydesdale%20horse | Biology and health sciences | Horses | Animals |
A speedometer or speed meter is a gauge that measures and displays the instantaneous speed of a vehicle. Now universally fitted to motor vehicles, they started to be available as options in the early 20th century, and as standard equipment from about 1910 onwards. Other vehicles may use devices analogous to the speedometer with different means of sensing speed, eg. boats use a pit log, while aircraft use an airspeed indicator.
Charles Babbage is credited with creating an early type of a speedometer, which was usually fitted to locomotives.
The electric speedometer was invented by the Croat Josip Belušić in 1888 and was originally called a velocimeter.
History
The speedometer was originally patented by Josip Belušić (Giuseppe Bellussich) in 1888. He presented his invention at the 1889 Exposition Universelle in Paris. His invention had a pointer and a magnet, using electricity to work.
German inventor Otto Schultze patented his version (which, like Belušić's, ran on eddy currents) on 7 October 1902.
Operation
Mechanical
Many speedometers use a rotating flexible cable driven by gearing linked to the vehicle's transmission. The early Volkswagen Beetle and many motorcycles, however, use a cable driven from a front wheel.
Some early mechanical speedometers operated on the governor principle where a rotating weight acting against a spring moved further out as the speed increased, similar to the governor used on steam engines. This movement was transferred to the pointer to indicate speed.
This was followed by the Chronometric speedometer where the distance traveled was measured over a precise interval of time (Some Smiths speedometers used 3/4 of a second) measured by an escapement. This was transferred to the speedometer pointer. The chronometric speedometer is tolerant of vibration and was used in motorcycles up to the 1970s.
When the vehicle is in motion, a speedometer gear assembly turns a speedometer cable, which then turns the speedometer mechanism itself. A small permanent magnet affixed to the speedometer cable interacts with a small aluminium cup (called a speedcup) attached to the shaft of the pointer on the analogue speedometer instrument. As the magnet rotates near the cup, the changing magnetic field produces eddy current in the cup, which itself produces another magnetic field. The effect is that the magnet exerts a torque on the cup, "dragging" it, and thus the speedometer pointer, in the direction of its rotation with no mechanical connection between them. | Speedometer | Wikipedia | 506 | 576681 | https://en.wikipedia.org/wiki/Speedometer | Technology | Measuring instruments | null |
The pointer shaft is held toward zero by a fine torsion spring. The torque on the cup increases with the speed of rotation of the magnet. Thus an increase in the speed of the car will twist the cup and speedometer pointer against the spring. The cup and pointer will turn until the torque of the eddy currents on the cup are balanced by the opposing torque of the spring, and then stop. Given the torque on the cup is proportional to the car's speed, and the spring's deflection is proportional to the torque, the angle of the pointer is also proportional to the speed, so that equally spaced markers on the dial can be used for gaps in speed. At a given speed, the pointer will remain motionless and point to the appropriate number on the speedometer's dial.
The return spring is calibrated such that a given revolution speed of the cable corresponds to a specific speed indication on the speedometer. This calibration must take into account several factors, including ratios of the tail shaft gears that drive the flexible cable, the final drive ratio in the differential, and the diameter of the driven tires.
One of the key disadvantages of the eddy current speedometer is that it cannot show the vehicle speed when running in reverse gear since the cup would turn in the opposite direction – in this scenario, the needle would be driven against its mechanical stop pin on the zero position.
Electronic
Many modern speedometers are electronic. In designs derived from earlier eddy-current models, a rotation sensor mounted in the transmission delivers a series of electronic pulses whose frequency corresponds to the (average) rotational speed of the driveshaft, and therefore the vehicle's speed, assuming the wheels have full traction. The sensor is typically a set of one or more magnets mounted on the output shaft or (in transaxles) differential crown wheel, or a toothed metal disk positioned between a magnet and a magnetic field sensor. As the part in question turns, the magnets or teeth pass beneath the sensor, each time producing a pulse in the sensor as they affect the strength of the magnetic field it is measuring. Alternatively, particularly in vehicles with multiplex wiring, some manufacturers use the pulses coming from the ABS wheel sensors which communicate to the instrument panel via the CAN Bus. Most modern electronic speedometers have the additional ability over the eddy current type to show the vehicle's speed when moving in reverse gear. | Speedometer | Wikipedia | 487 | 576681 | https://en.wikipedia.org/wiki/Speedometer | Technology | Measuring instruments | null |
A computer converts the pulses to a speed and displays this speed on an electronically controlled, analogue-style needle or a digital display. Pulse information is also used for a variety of other purposes by the ECU or full-vehicle control system, e.g. triggering ABS or traction control, calculating average trip speed, or increment the odometer in place of it being turned directly by the speedometer cable.
Another early form of electronic speedometer relies upon the interaction between a precision watch mechanism and a mechanical pulsator driven by the car's wheel or transmission. The watch mechanism endeavours to push the speedometer pointer toward zero, while the vehicle-driven pulsator tries to push it toward infinity. The position of the speedometer pointer reflects the relative magnitudes of the outputs of the two mechanisms.
Virtual Speedometer
A virtual speedometer is a computer-generated tool that displays the current speed of a vehicle or object. The virtual speedometer typically calculates the object's speed based on the distance it travels over time. Such speedometers are programmed using programming languages such as HTML, CSS, and Javascript. The program uses the mobile device's GPS module.
Consistent use of the GPS module on mobile devices can result in faster battery drain. Furthermore, virtual speedometers calculate speed by measuring the distance and time between two points using GPS signals. However, various environmental factors such as weather conditions, terrain, and obstructions can interfere with the accuracy of these signals and result in inaccurate speed readings.
Bicycle speedometers | Speedometer | Wikipedia | 312 | 576681 | https://en.wikipedia.org/wiki/Speedometer | Technology | Measuring instruments | null |
Typical bicycle speedometers measure the time between each wheel revolution and give a readout on a small, handlebar-mounted digital display. The sensor is mounted on the bike at a fixed location, pulsing when the spoke-mounted magnet passes by. In this way, it is analogous to an electronic car speedometer using pulses from an ABS sensor, but with a much cruder time/distance resolution – typically one pulse/display update per revolution, or as seldom as once every 2–3 seconds at low speed with a wheel. However, this is rarely a critical problem, and the system provides frequent updates at higher road speeds where the information is of more importance. The low pulse frequency also has little impact on measurement accuracy, as these digital devices can be programmed by wheel size, or additionally by wheel or tire circumference to make distance measurements more accurate and precise than a typical motor vehicle gauge. However, these devices carry some minor disadvantages in requiring power from batteries that must be replaced every so often in the receiver (and sensor, for wireless models), and, in wired models, the signal is carried by a thin cable that is much less robust than that used for brakes, gears, or cabled speedometers.
Other, usually older bicycle speedometers are cable driven from one or other wheel, as in the motorcycle speedometers described above. These do not require battery power, but can be relatively bulky and heavy, and may be less accurate. The turning force at the wheel may be provided either from a gearing system at the hub (making use of the presence of e.g. a hub brake, cylinder gear, or dynamo) as per a typical motorcycle, or with a friction wheel device that pushes against the outer edge of the rim (same position as rim brakes, but on the opposite edge of the fork) or the sidewall of the tire itself. The former type is quite reliable and low maintenance but needs a gauge and hub gearing properly matched to the rim and tire size, whereas the latter requires little or no calibration for a moderately accurate readout (with standard tires, the "distance" covered in each wheel rotation by a friction wheel set against the rim should scale fairly linearly with wheel size, almost as if it were rolling along the ground itself) but are unsuitable for off-road use, and must be kept properly tensioned and clean of road dirt to avoid slipping or jamming. | Speedometer | Wikipedia | 494 | 576681 | https://en.wikipedia.org/wiki/Speedometer | Technology | Measuring instruments | null |
Error
Most speedometers have tolerances of some ±10%, mainly due to variations in tire diameter. Sources of error due to tire diameter variations are wear, temperature, pressure, vehicle load, and nominal tire size. Vehicle manufacturers usually calibrate speedometers to read high by an amount equal to the average error, to ensure that their speedometers never indicate a lower speed than the actual speed of the vehicle, to ensure they are not liable for drivers violating speed limits.
Excessive speedometer errors after manufacture can come from several causes, but most commonly is due to nonstandard tire diameter, in which case the error is:
Nearly all tires now have their size is shown as "T/A_W" on the side of the tire (See: Tire code), and the tires.
For example, a standard tire is "185/70R14" with diameter = 2*185*(70/100)+(14*25.4) = 614.6 mm (185x70/1270 + 14 = 24.20 in). Another is "195/50R15" with 2*195*(50/100)+(15*25.4) = 576.0 mm (195x50/1270 + 15 = 22.68 in). Replacing the first tire (and wheels) with the second (on 15" = 381 mm wheels), a speedometer reads 100 * ((614.6/576) - 1) = 100 * (24.20/22.68 - 1) = 6.7% higher than the actual speed. At an actual speed of 100 km/h (60 mph), the speedometer will indicate 100 x 1.067 = 106.7 km/h (60 * 1.067 = 64.02 mph), approximately.
In the case of wear, a new "185/70R14" tire of 620 mm (24.4 inch) diameter will have ≈8 mm tread depth, at legal limit this reduces to 1.6 mm, the difference being 12.8 mm in diameter or 0.5 inches which is 2% in 620 mm (24.4 inches). | Speedometer | Wikipedia | 454 | 576681 | https://en.wikipedia.org/wiki/Speedometer | Technology | Measuring instruments | null |
International agreements
In many countries the legislated error in speedometer readings is ultimately governed by the United Nations Economic Commission for Europe (UNECE) Regulation 39, which covers those aspects of vehicle type approval that relate to speedometers. The main purpose of the UNECE regulations is to facilitate trade in motor vehicles by agreeing on uniform type approval standards rather than requiring a vehicle model to undergo different approval processes in each country where it is sold.
European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers are similar to the UNECE regulation in that they specify that:
The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
The indicated speed must not be more than 110 percent of the true speed plus at specified test speeds. For example, at , the indicated speed must be no more than .
The standards specify both the limits on accuracy and many of the details of how it should be measured during the approvals process. For example, the test measurements should be made (for most vehicles) at , and at a particular ambient temperature and road surface. There are slight differences between the different standards, for example in the minimum accuracy of the equipment measuring the true speed of the vehicle.
The UNECE regulation relaxes the requirements for vehicles mass-produced following type approval. At Conformity of Production Audits the upper limit on indicated speed is increased to 110 percent plus for cars, buses, trucks, and similar vehicles, and 110 percent plus for two- or three-wheeled vehicles that have a maximum speed above (or a cylinder capacity, if powered by a heat engine, of more than ). European Union Directive 2000/7/EC, which relates to two- and three-wheeled vehicles, provides similar slightly relaxed limits in production.
Australia
There were no Australian Design Rules in place for speedometers in Australia before July 1988. They had to be introduced when speed cameras were first used. This means there are no legally accurate speedometers for these older vehicles. All vehicles manufactured on or after 1 July 2007, and all models of vehicle introduced on or after 1 July 2006, must conform to UNECE Regulation 39. | Speedometer | Wikipedia | 454 | 576681 | https://en.wikipedia.org/wiki/Speedometer | Technology | Measuring instruments | null |
The speedometers in vehicles manufactured before these dates but after 1 July 1995 (or 1 January 1995 for forward control passenger vehicles and off-road passenger vehicles) must conform to the previous Australian design rule. This specifies that they need only display the speed to an accuracy of ±10% at speeds above 40 km/h, and there is no specified accuracy at all for speeds below 40 km/h.
All vehicles manufactured in Australia or imported for supply to the Australian market must comply with the Australian Design Rules. The state and territory governments may set policies for the tolerance of speed over the posted speed limits that may be lower than the 10% in the earlier versions of the Australian Design Rules permitted, such as in Victoria. This has caused some controversy since it would be possible for a driver to be unaware that they are speeding should their vehicle be fitted with an under-reading speedometer.
United Kingdom
The amended Road Vehicles (Construction and Use) Regulations 1986 permits the use of speedometers that meet either the requirements of EC Council Directive 75/443 (as amended by Directive 97/39) or UNECE Regulation 39.
The Motor Vehicles (Approval) Regulations 2001 permits single vehicles to be approved. As with the UNECE regulation and the EC Directives, the speedometer must never show an indicated speed less than the actual speed. However, it differs slightly from them in specifying that for all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph.
For example, if the vehicle is actually traveling at 50 mph, the speedometer must not show more than 61.25 mph or less than 50 mph.
United States
Federal standards in the United States allow a maximum 5 mph error at a speed of 50 mph on speedometer readings for commercial vehicles. Aftermarket modifications, such as different tire and wheel sizes or different differential gearing, can cause speedometer inaccuracy.
Regulation in the US
Starting with U.S. automobiles manufactured on or after 1 September 1979, the NHTSA required speedometers to have a special emphasis on 55 mph (90 km/h) and display no more than a maximum speed of 85 mph (136 km/h). On 25 March 1982, the NHTSA revoked the rule because no "significant safety benefits" could come from maintaining the standard.
GPS
GPS devices can measure speeds in two ways: | Speedometer | Wikipedia | 500 | 576681 | https://en.wikipedia.org/wiki/Speedometer | Technology | Measuring instruments | null |
The first and simpler method is based on how far the receiver has moved since the last measurement. Such speed calculations are not subject to the same sources of error as the vehicle's speedometer (wheel size, transmission/drive ratios). Instead, the GPS's positional accuracy, and therefore the accuracy of its calculated speed, is dependent on the satellite signal quality at the time. Speed calculations will be more accurate at higher speeds when the ratio of positional error to positional change is lower. The GPS software may also use a moving average calculation to reduce error. Some GPS devices do not take into account the vertical position of the car so will under-report the speed by the road's gradient.
Alternatively, the GPS may take advantage of the Doppler effect to estimate its velocity. In ideal conditions, the accuracy for commercial devices is within 0.2–0.5 km/h, but it may worsen if the signal quality degrades.
As mentioned in the satnav article, GPS data has been used to overturn a speeding ticket; the GPS logs showed the defendant traveling below the speed limit when they were ticketed. That the data came from a GPS device was likely less important than the fact that it was logged; logs from the vehicle's speedometer could likely have been used instead, had they existed. | Speedometer | Wikipedia | 273 | 576681 | https://en.wikipedia.org/wiki/Speedometer | Technology | Measuring instruments | null |
Compsognathus (; Greek kompsos/κομψός; "elegant", "refined" or "dainty", and gnathos/γνάθος; "jaw") is a genus of small, bipedal, carnivorous theropod dinosaur. Members of its single species Compsognathus longipes could grow to around the size of a chicken. They lived about 150 million years ago, during the Tithonian age of the late Jurassic period, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany in the 1850s and the second in France more than a century later. Today, C. longipes is the only recognized species, although the larger specimen discovered in France in the 1970s was once thought to belong to a separate species and named C. corallestris.
Many presentations still describe Compsognathus as "chicken-sized" dinosaurs because of the size of the German specimen, which is now believed to be a juvenile. Compsognathus longipes is one of the few dinosaur species whose diet is known with certainty: the remains of small, agile lizards are preserved in the bellies of both specimens. Teeth discovered in Portugal may be further fossil remains of the genus.
Although not recognized as such at the time of its discovery, Compsognathus is the first theropod dinosaur known from a reasonably complete fossil skeleton. Until the 1990s, it was the smallest-known non-avialan dinosaur, with the preceding centuries incorrectly labelling them as the closest relative of Archaeopteryx.
Discovery and species
Compsognathus is known from two almost complete skeletons. The German specimen (specimen number BSP AS I 563) stems from limestone deposits in Bavaria and was part of the collection of the physician and fossil collector Joseph Oberndorfer. Oberndorfer lent the specimen to paleontologist Johann A. Wagner, who published a brief discussion in 1859, where he coined the name Compsognathus longipes. Wagner did not recognise Compsognathus as a dinosaur, but instead described it as one of the "most curious forms among the lizards". He published a more detailed description in 1861. In 1866, Oberndorfer's collection, including the Compsognathus specimen, was acquired by the paleontological state collection in Munich. | Compsognathus | Wikipedia | 494 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
Both the year of discovery and the exact locality of the German specimen are unknown, possibly because Oberndorfer did not reveal details of the discovery to prevent other collectors from exploiting the locality; later authors have suggested that the German specimen was probably discovered during the 1850s. Weathering of the slab on which the fossil is preserved indicates that it was collected from a pile of waste rock left behind by quarrying. The specimen either stems from Jachenhausen or the region Riedenburg–Kehlheim. All possible localities are part of lagoonal deposits of the Painten Formation, and date to the latest part of the late Kimmeridgian or the earlier part of the early Tithonian. In the Jurassic, the region was part of the Solnhofen archipelago. The limestone of the area, the Solnhofen limestone, had been quarried for centuries, and yielded such well-preserved fossils as Archaeopteryx with feather impressions and pterosaurs with imprints of their wing membranes.
In two publications in 1868 and 1870, Thomas Huxley, a major proponent of Charles Darwin's theory of evolution, compared Compsognathus with Archaeopteryx, which was considered the earliest known bird. Following earlier suggestions by Carl Gegenbaur and Edward Drinker Cope, Huxley found that Archaeopteryx was closely similar to Compsognathus, and referred to the latter as a "bird-like reptile". He concluded that birds must have evolved from dinosaurs, an assessment that established Compsognathus as one of the most widely known dinosaurs. The specimen has since been studied by many prominent paleontologists, including Othniel Charles Marsh, who visited Munich in 1881. The German paleontologist J.G. Baur, who worked as an assistant of Marsh, removed the right ankle from the slab for illustration and study; this removed part got lost since. Although Baur published a detailed study of the ankle in 1882, which is now the only available source of information of this part of the skeleton, his reconstruction was later found to be inconsistent with corresponding impressions on the slab. John Ostrom thoroughly described the German specimen as well as the newly discovered French specimen in 1978, making Compsognathus one of the best-known small theropods at that time. He also concluded that the German specimen likely belongs to an immature individual. | Compsognathus | Wikipedia | 492 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
The larger French specimen (Y85R M4M) was discovered in around 1971 in the Portlandian lithographic limestone of Canjuers near Nice. It dates to the lower Tithonian, as indicated by ammonite index fossils. As Solnhofen, Canjures was famous for its limestone plates, which were quarried and sold under the name "dalles de Provence". The specimen was originally part of a large private fossil collection of Louis Ghirardi, the owner of the Canjures quarries. The collection, including the Compsognathus specimen, was sold to the National Museum of Natural History in Paris in 1983. Alain Bidar and Gérard Thomel, in a brief 1972 description, announced the new find under a separate species, Compsognathus corallestris. A more comprehensive description followed in the same year. According to these authors, the new species differed from the German species in its larger size and modified, flipper-like hand. Ostrom, Jean-Guy Michard and others have since relabeled it as another example of Compsognathus longipes. In 1984, George Callison and Helen Quimby identified the smaller German specimen as a juvenile of the same species.
Collector Heinrich Fischer had originally labeled a partial foot consisting of three metatarsals and a phalanx, from the Solnhofen area, as belonging to Compsognathus longipes. This identification was rejected by Wilhelm Dames, when he described the specimen for the first time in 1884. Friedrich von Huene, in 1925 and 1932, also found that the foot did probably not belong to Compsognathus itself but to a closely related genus. Ostrom, in his 1978 monography, questioned the attribution of this fossil to Compsognathus once more. Jens Zinke, in 1998, assigned forty-nine isolated teeth from the Guimarota coal mine of Portugal to the genus. Zinke found that these teeth are not identical to those of Compsognathus longipes, having serrations on the front edge, and thus labeled the teeth as Compsognathus sp. (of unknown species).
Description | Compsognathus | Wikipedia | 456 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
For decades, Compsognathus was known as the smallest known non-avian dinosaur, although some dinosaurs discovered later, such as Mahakala and Microraptor, were even smaller. The German specimen was estimated to be and in length by separate authors, while the larger French specimen was estimated at and in length. The height at the hip has been estimated at for the German specimen and at for the French specimen. The German specimen was estimated to have weighed and , and the French specimen and . Compared to other compsognathids, the larger French specimen would have been similar in size to larger Sinosauropteryx specimens, but smaller than Huaxiagnathus and Mirischia.
Compsognathus were small, bipedal animals with long hind legs and longer tails, which they used for balance during locomotion. The forelimbs were smaller than the hindlimbs. The hand bore two large, clawed digits and a third, smaller digit that may have been non-functional. Their delicate skulls were narrow and long, with tapered snouts. The skull had five pairs of fenestrae (skull openings), the largest of which was for the orbit (eye socket), with the eyes being larger in proportion to the rest of the skull. The lower jaw was slender and had no mandibular fenestra, a hole in the side of the lower jawbone commonly seen in archosaurs. | Compsognathus | Wikipedia | 292 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
The teeth were small and pointed, suited for its diet of small vertebrates and possibly other small animals, such as insects. The German specimen had three teeth in each premaxilla (front bone of the lower jaw), 15 or 16 teeth in each maxilla, and 18 teeth in the lower jaw. The French specimen had more teeth, including four in each premaxilla, 17 or 18 in the maxilla, and at least 21 teeth in the dentary. Compsognathids were unique among theropods in having tooth crowns that curved backwards at two thirds of their height, while their mid-parts were straight; also, the crowns had expanded bases. In Compsognathus, the frontmost teeth of the upper and lower jaws were unserrated, while those further back had fine serrations on their rear edges. In the German specimen, the crowns were around two times higher than wide in the front of the jaws but diminished in height further back, with the last tooth about as high as wide. The German specimen also shows a diastema (tooth gap) behind the first three teeth of the premaxilla. As such a gap was not present in the French specimen, Peyer suggested that additional teeth were possibly present in this region the German specimen.
The number of digits on the hand of Compsognathus has been a source of debate. For much of its history, Compsognathus was typically depicted with three digits, as is typical for theropods. However, the type specimen only preserved phalanges from the first two digits, leading to the suggestion that Compsognathus bore only two functional digits, with the third metacarpal being extremely slender and reduced. Study of the French specimen indicated that the third digit bore at least one or two small phalanges. However, there remains no evidence for an ungual phalanx on the third digit, so the digit may have been reduced and non-functional.
Integument | Compsognathus | Wikipedia | 409 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
Some relatives of Compsognathus, namely Sinosauropteryx and Sinocalliopteryx, have been preserved with the remains of simple feathers covering the body like fur, prompting some scientists to suggest that Compsognathus might have been feathered in a similar way. Consequently, many depictions of Compsognathus show them with coverings of downy proto-feathers. However, no feathers or feather-like covering have been preserved with Compsognathus fossils, in contrast to Archaeopteryx, which are found in the same sediments. Karin Peyer, in 2006, reported skin impressions preserved on the side of the tail starting at the 13th tail vertebra. The impressions showed small bumpy tubercles, similar to the scales found on the tail and hind legs of Juravenator. Additional scales had in 1901 been reported by Von Huene, in the abdominal region of the German Compsognathus, but Ostrom subsequently disproved this interpretation; in 2012 they were by Achim Reisdorf seen as plaques of adipocere, corpse wax.
Like Compsognathus, and unlike Sinosauropteryx, a patch of fossilized skin from the tail and hindlimb of the possible relative Juravenator starki shows mainly scales, though there is some indication that simple feathers were also present in the preserved areas. This may mean that a feather covering was not ubiquitous in this group of dinosaurs, or maybe that some species had fewer feathers than others.
Classification | Compsognathus | Wikipedia | 312 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
Originally classified as a lizard, the dinosaurian affinities of Compsognathus were first noted by Gegenbaur, Cope, and Huxley between 1863 and 1868. Cope, in 1870, classified Compsognathus within a new clade of dinosaurs, the Symphypoda, which also contained Ornithotarsus (today classified as Hadrosaurus). Later, both genera were found to belong to other groups of Cope's classification of dinosaurs: Compsognathus to the Gonipoda (equivalent to Theropoda, in which it is now classified), and Ornithotarsus to the Orthopoda (equivalent to Ornithischia). Huxley, in 1870, rejected Cope's dinosaur classification scheme, and instead proposed the new clade Ornithoscelida, in which he included the Dinosauria (comprising several forms now considered as ornithischians) and another new clade, the Compsognatha, which contained Compsognathus as the only member. Later, these groups fell into disuse, although a resurrection of the Ornithoscelida was proposed in 2017. The group Compsognatha was used for the last time by Marsh in a 1896 publication, where it was treated as a suborder of Theropoda. In the same publication, Marsh erected the new family Compsognathidae. Friedrich von Huene, in 1914, erected the new infraorder Coelurosauria, which includes the Compsognathidae amongst other families of small theropods; this classification remained in use since. | Compsognathus | Wikipedia | 340 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
The Compsognathidae are a group of mostly small dinosaurs from the late Jurassic and early Cretaceous periods of China, Europe and South America. For many years, Compsognathus was the only member known, but in recent decades paleontologists have discovered several related genera. The clade includes Aristosuchus, Huaxiagnathus, Mirischia, Sinosauropteryx, and perhaps Juravenator and Scipionyx. At one time, Mononykus was proposed as a member of the family, but this was rejected by Chen and coauthors in a 1998 paper; they considered the similarities between Mononykus and the compsognathids to be an example of convergent evolution. The position of Compsognathus and its relatives within the coelurosaur group is uncertain. Some, such as theropod expert Thomas Holtz Jr. and co-authors Ralph Molnar and Phil Currie in the landmark 2004 text Dinosauria, hold the family as the most basal of the coelurosaurs, while others as part of the Maniraptora.
For almost a century, Compsognathus longipes was the only well-known small theropod species. This led to comparisons with Archaeopteryx and to suggestions of an especially close relationship with birds. In fact, Compsognathus, rather than Archaeopteryx, piqued Huxley's interest in the origin of birds. The two animals share similarities in shape and proportions, so many in fact that two specimens of Archaeopteryx, the "Eichstätt" and the "Solnhofen", were for a time misidentified as those of Compsognathus. Many other types of theropod dinosaurs, such as maniraptorans, are now known to have been more closely related to birds.
Below is a simplified cladogram placing Compsognathus in Compsognathidae by Senter et al. in 2012.
Here is an alternative phylogeny, published by Cau in 2024, with both specimens in bold.
Paleobiology
In a 2001 study conducted by Bruce Rothschild and other paleontologists, nine foot bones referred to Compsognathus were examined for signs of stress fracture, but none were found. | Compsognathus | Wikipedia | 478 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
Habitat
Bidar and colleagues, in their 1972 description of the French specimen, argued that this specimen had webbed hands which would look like flippers in life. This interpretation was based on a supposed impression of the flipper that consists of several undulating wrinkles running parallel to the forelimb on the surface of the slab. In a 1975 popular book, L. Beverly Halstead depicts the animal as an amphibious dinosaur capable of feeding on aquatic prey and swimming out of reach of larger predators. Ostrom debunked this hypothesis, noting that the forelimb of the French specimen is poorly preserved, and that the wrinkles extend well beyond the skeleton and thus are likely sedimentary structures unrelated to the fossil.
Diet
The remains of a lizard in the German specimen's thoracic cavity show that Compsognathus preyed on small vertebrates. Marsh, who examined the specimen in 1881, thought that this small skeleton in the Compsognathus belly was an embryo, but in 1903, Franz Nopcsa concluded that it was a lizard. Ostrom identified the remains as belonging to a lizard of the genus Bavarisaurus, which he concluded was a fast and agile runner owing to its long tail and limb proportions. This in turn led to the conclusion that its predators, Compsognathus, must have had sharp vision and the ability to rapidly accelerate and outrun the lizard. Conrad made the lizard found in the thoracic cavity of the German specimen of Compsognathus the holotype of a new species Schoenesmahl dyspepsia. The lizard is in several pieces, indicating that the Compsognathus must have dismembered it while restraining it with its hands and teeth, and then swallowed the remains whole; a similar strategy is used by modern predatory birds. The French specimen's gastric contents consist of unidentified lizards or sphenodontids. | Compsognathus | Wikipedia | 392 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
Possible eggs
The plate of the German Compsognathus shows several circular irregularities in diameter near the skeletal remains. Peter Griffiths interpreted them as immature eggs in 1993. However, later researchers have doubted their connection to the genus because they were found outside the body cavity of the animal. A well-preserved fossil of a Sinosauropteryx, a genus related to Compsognathus, shows two oviducts bearing two unlaid eggs. These proportionally larger and less numerous eggs of Sinosauropteryx cast further doubt on the original identification of the purported Compsognathus eggs. In 1964 German geologist Karl Werner Barthel had explained the discs as gas bubbles formed in the sediment because of the putrefaction of the carcass.
Speed
In 2007, William Sellers and Phillip Manning estimated a maximum speed of based on a computer model of the skeleton and muscles. This estimate has been criticized by other scholars.
Paleoenvironment
During the late Jurassic, Europe was a dry, tropical archipelago at the edge of the Tethys Sea. The fine limestone in which the skeletons of Compsognathus have been found originated in calcite from the shells of marine organisms. Both the German and French areas where Compsognathus specimens have been preserved were lagoons situated between the beaches and coral reefs of the Jurassic European islands in the Tethys Sea. Contemporaries of Compsognathus longipes include the early avialan Archaeopteryx lithographica and the pterosaurs Rhamphorhynchus muensteri and Pterodactylus antiquus. The same sediments in which Compsognathus have been preserved also contain fossils of a number of marine animals such as fish, crustaceans, echinoderms and marine mollusks, confirming the coastal habitat of this theropod. No other dinosaur has been found in association with Compsognathus, indicating that these little dinosaurs might in fact have been the top land predator in these islands. | Compsognathus | Wikipedia | 414 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
Taphonomy
Much discussion revolved around the taphonomy of the German specimen, i.e. how the individual died and became fossilized. Reisdorf and Wuttke, in 2012, speculated about the events that lead to the death and transportation of the specimen to its place of burial. First, the individual must have been brought into the lagoon from its habitat, which probably was on the surrounding islands. It is possible that a flash flood swept the animal into the sea, in which case it likely died by drowning. It is also possible that the animal swam or drifted onto the sea, or that it rafted on plants, and was then transported by surface currents to its place of burial. In any case, the specimen would have arrived on the sea floor within a few hours after its death, as otherwise gases forming in its body cavity would have prevented it from sinking in one piece. Water depth at the burial site would have been large enough to prevent refloating of the carcass after such gases were produced. Rounded structures on the slab might have been formed by the release of these gases.
Taphonomic reconstructions are complicated as the exact locality and the position and orientation of the fossil within the sediments is no longer known. As a compression fossil, the specimen would originally have been preserved on both the upper surface of a layer and the lower surface of the subsequent layer (i.e., on a slab and its counter-slab); the counter-slab is now lost. Reisdorf and Wuttke, in 2012, argued that the front and hind limbs of the left side of the body were better (still connected together) than those of the right side. This suggests that the specimen is located on the bottom side of the upper slab, and was lying on its left side. The German specimen was preserved with a high degree of articulation – only the skull, hands, cervical ribs and gastralia show disarticulation. The braincase was displaced behind the skull, the first tail vertebra was rotated by 90°, and the tail shows a break between the seventh and eighth tail vertebra. | Compsognathus | Wikipedia | 435 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
In both Compsognathus specimens, the neck is strongly curved, with the head coming to rest above the pelvis; the spine of the tail was likewise curved. This posture, known as the death pose, is found in many vertebrate fossils, and the German Compsognathus specimen was central in several studies that sought to explain this phenomenon. The physician Moodie, in 1918, suggested that the death pose in Compsognathus and similar fossils was the result of an opisthotonus – death throes causing spastic stiffening of the back musculature – while the animal was dying. This hypothesis was soon challenged by paleontologist Friedrich von Huene, who argued that the death pose was the result of desiccation and therefore occurred only after the death. Peter Wellnhofer, in 1991, argued that death poses resulted from the elastic pull of the ligaments, which are released after death. The veterinarian Cynthia Faux and the paleontologist Kevin Padian, in a 2007 study that gained much attention, supported the original opisthotonus hypothesis of Moodie. These authors furthermore argued that upon death, muscles are relaxed and body parts can be easily moved relative to each other. Since opisthotonic postures are already established during death, they may only be preserved if the animal dies in place and becomes buried rapidly. This contradicts previous interpretations on the environment and taphonomy of Compsognathus and other fossils from the Solnhofen limestones, which assumed very slow burial at the bottom of lagoons into which the carcasses were transported from nearby islands. Reisdorf and Wuttke concluded that the death posture indeed resulted from the release of ligaments, more specifically the , which spans the spine from the neck to tail in modern birds. The release of this ligament would have occurred gradually while the surrounding muscle tissue decayed, and only after the carcass was transported to its final site of deposition. | Compsognathus | Wikipedia | 406 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
The bottom water of the lagoon was likely anaerobic (devoid in oxygen), resulting in a sea floor devoid of life except for microbial mats, and therefore preventing scavenging of the carcass. In the trunk region of the German specimen, the surface of the slab is markedly different in texture to the surrounding areas of the slab, showing irregular, nodular surfaces within depressions. Ostrom, in 1978, interpreted these structures as traces of weathering that took place just before the fossil was collected. Nopcsa, in 1903, instead suggested that these structures resulted from decomposing tissue of the carcass. Reisdorf and Wuttke, in their 2012 study, suggested that the structures are the remains of adipocere (corpse wax formed by bacteria) that formed around the carcass before burial. Such adipocere would have helped in conserving the state of articulation of the fossil for years when burial was very slow. The presence of adipocere would possibly rule out hypersalinity (very high salt contents) of the bottom water, because such conditions appear to be unfavorable for the adipocere producing bacteria.
In popular culture
Compsognathus is one of the more popular dinosaurs. For a long time it was considered unique in its small size, which is commonly compared to that of a chicken. These animals have appeared in the Jurassic Park franchise: in the films The Lost World: Jurassic Park, Jurassic Park III, Jurassic World: Fallen Kingdom and Jurassic World Dominion and in the series Camp Cretaceous, where they were often nicknamed Compies. In The Lost World: Jurassic Park, one of the characters incorrectly identifies the species as "Compsognathus triassicus", combining the genus name of Compsognathus longipes with the specific name of Procompsognathus triassicus, a distantly related small carnivore featured in the Jurassic Park novels. | Compsognathus | Wikipedia | 400 | 577188 | https://en.wikipedia.org/wiki/Compsognathus | Biology and health sciences | Theropods | Animals |
In mathematics, the magnitude or size of a mathematical object is a property which determines whether the object is larger or smaller than other objects of the same kind. More formally, an object's magnitude is the displayed result of an ordering (or ranking) of the class of objects to which it belongs. Magnitude as a concept dates to Ancient Greece and has been applied as a measure of distance from one object to another. For numbers, the absolute value of a number is commonly applied as the measure of units between a number and zero.
In vector spaces, the Euclidean norm is a measure of magnitude used to define a distance between two points in space. In physics, magnitude can be defined as quantity or distance. An order of magnitude is typically defined as a unit of distance between one number and another's numerical places on the decimal scale.
History
Ancient Greeks distinguished between several types of magnitude, including:
Positive fractions
Line segments (ordered by length)
Plane figures (ordered by area)
Solids (ordered by volume)
Angles (ordered by angular magnitude)
They proved that the first two could not be the same, or even isomorphic systems of magnitude. They did not consider negative magnitudes to be meaningful, and magnitude is still primarily used in contexts in which zero is either the smallest size or less than all possible sizes.
Numbers
The magnitude of any number is usually called its absolute value or modulus, denoted by .
Real numbers
The absolute value of a real number r is defined by:
Absolute value may also be thought of as the number's distance from zero on the real number line. For example, the absolute value of both 70 and −70 is 70.
Complex numbers
A complex number z may be viewed as the position of a point P in a 2-dimensional space, called the complex plane. The absolute value (or modulus) of z may be thought of as the distance of P from the origin of that space. The formula for the absolute value of is similar to that for the Euclidean norm of a vector in a 2-dimensional Euclidean space:
where the real numbers a and b are the real part and the imaginary part of z, respectively. For instance, the modulus of is . Alternatively, the magnitude of a complex number z may be defined as the square root of the product of itself and its complex conjugate, , where for any complex number , its complex conjugate is .
(where ).
Vector spaces
Euclidean vector space | Magnitude (mathematics) | Wikipedia | 492 | 577301 | https://en.wikipedia.org/wiki/Magnitude%20%28mathematics%29 | Mathematics | Linear algebra | null |
A Euclidean vector represents the position of a point P in a Euclidean space. Geometrically, it can be described as an arrow from the origin of the space (vector tail) to that point (vector tip). Mathematically, a vector x in an n-dimensional Euclidean space can be defined as an ordered list of n real numbers (the Cartesian coordinates of P): x = [x1, x2, ..., xn]. Its magnitude or length, denoted by , is most commonly defined as its Euclidean norm (or Euclidean length):
For instance, in a 3-dimensional space, the magnitude of [3, 4, 12] is 13 because
This is equivalent to the square root of the dot product of the vector with itself:
The Euclidean norm of a vector is just a special case of Euclidean distance: the distance between its tail and its tip. Two similar notations are used for the Euclidean norm of a vector x:
A disadvantage of the second notation is that it can also be used to denote the absolute value of scalars and the determinants of matrices, which introduces an element of ambiguity.
Normed vector spaces
By definition, all Euclidean vectors have a magnitude (see above). However, a vector in an abstract vector space does not possess a magnitude.
A vector space endowed with a norm, such as the Euclidean space, is called a normed vector space. The norm of a vector v in a normed vector space can be considered to be the magnitude of v.
Pseudo-Euclidean space
In a pseudo-Euclidean space, the magnitude of a vector is the value of the quadratic form for that vector.
Logarithmic magnitudes
When comparing magnitudes, a logarithmic scale is often used. Examples include the loudness of a sound (measured in decibels), the brightness of a star, and the Richter scale of earthquake intensity. Logarithmic magnitudes can be negative. In the natural sciences, a logarithmic magnitude is typically referred to as a level.
Order of magnitude
Orders of magnitude denote differences in numeric quantities, usually measurements, by a factor of 10—that is, a difference of one digit in the location of the decimal point.
Other mathematical measures | Magnitude (mathematics) | Wikipedia | 456 | 577301 | https://en.wikipedia.org/wiki/Magnitude%20%28mathematics%29 | Mathematics | Linear algebra | null |
A tunnel boring machine (TBM), also known as a "mole" or a "worm", is a machine used to excavate tunnels. Tunnels are excavated through hard rock, wet or dry soil, or sand, each of which requires specialized technology.
Tunnel boring machines are an alternative to drilling and blasting (D&B) methods and "hand mining".
TBMs limit the disturbance to the surrounding ground and produce a smooth tunnel wall. This reduces the cost of lining the tunnel, and is suitable for use in urban areas. TBMs are expensive to construct, and larger ones are challenging to transport. These fixed costs become less significant for longer tunnels.
TBM-bored tunnel cross-sections range from to date. Narrower tunnels are typically bored using trenchless construction methods or horizontal directional drilling rather than TBMs. TBM tunnels are typically circular in cross-section although they may be u-shaped, horseshoes, square or rectangular.
Tunneling speeds increase over time. The first TBM peaked at 4 meters per week. This increased to 16 meters per week four decades later. By the end of the 19th century, speeds had reached over 30 meters per week. 21st century rock TBMs can excavate over 700 meters per week, while soil tunneling machines can exceed 200 meters per week. Speed generally declines as tunnel size increases.
History
1800s
The first successful tunnelling shield was developed by Sir Marc Isambard Brunel to excavate the Thames Tunnel in 1825. However, this was only the invention of the shield concept and did not involve the construction of a complete tunnel boring machine, the digging still having to be accomplished by the then standard excavation methods.
The first boring machine reported to have been built was Henri Maus's Mountain Slicer. Commissioned by the King of Sardinia in 1845 to dig the Fréjus Rail Tunnel between France and Italy through the Alps, Maus had it built in 1846 in an arms factory near Turin. It consisted of more than 100 percussion drills mounted in the front of a locomotive-sized machine, mechanically power-driven from the entrance of the tunnel. The Revolutions of 1848 affected the funding, and the tunnel was not completed until 10 years later, by using less innovative and less expensive methods such as pneumatic drills. | Tunnel boring machine | Wikipedia | 461 | 577307 | https://en.wikipedia.org/wiki/Tunnel%20boring%20machine | Technology | Transport infrastructure | null |
In the United States, the first boring machine to have been built was used in 1853 during the construction of the Hoosac Tunnel in northwest Massachusetts. Made of cast iron, it was known as Wilson's Patented Stone-Cutting Machine, after inventor Charles Wilson. It drilled into the rock before breaking down (the tunnel was eventually completed more than 20 years later, and as with the Fréjus Rail Tunnel, by using less ambitious methods). Wilson's machine anticipated modern TBMs in the sense that it employed cutting discs, like those of a disc harrow, which were attached to the rotating head of the machine. In contrast to traditional chiseling or drilling and blasting, this innovative method of removing rock relied on simple metal wheels to apply a transient high pressure that fractured the rock.
In 1853, the American Ebenezer Talbot also patented a TBM that employed Wilson's cutting discs, although they were mounted on rotating arms, which in turn were mounted on a rotating plate. In the 1870s, John D. Brunton of England built a machine employing cutting discs that were mounted eccentrically on rotating plates, which in turn were mounted eccentrically on a rotating plate, so that the cutting discs would travel over almost all of the rock face that was to be removed. | Tunnel boring machine | Wikipedia | 258 | 577307 | https://en.wikipedia.org/wiki/Tunnel%20boring%20machine | Technology | Transport infrastructure | null |
The first TBM that tunneled a substantial distance was invented in 1863 and improved in 1875 by British Army officer Major Frederick Edward Blackett Beaumont (1833–1895); Beaumont's machine was further improved in 1880 by British Army officer Major Thomas English (1843–1935). In 1875, the French National Assembly approved the construction of a tunnel under the English Channel and the British Parliament supported a trial run using English's TBM. Its cutting head consisted of a conical drill bit behind which were a pair of opposing arms on which were mounted cutting discs. From June 1882 to March 1883, the machine tunneled, through chalk, a total of 1,840 m (6,036 ft). A French engineer, Alexandre Lavalley, who was also a Suez Canal contractor, used a similar machine to drill 1,669 m (5,476 ft) from Sangatte on the French side. However, despite this success, the cross-Channel tunnel project was abandoned in 1883 after the British military raised fears that the tunnel might be used as an invasion route. Nevertheless, in 1883, this TBM was used to bore a railway ventilation tunnel — in diameter and long — between Birkenhead and Liverpool, England, through sandstone under the Mersey River.
The Hudson River Tunnel was constructed from 1889 to 1904 using a Greathead shield TBM. The project used air compressed to to reduce cave-ins. However, many workers died via cave-in or decompression sickness.
1900s
During the late 19th and early 20th century, inventors continued to design, build, and test TBMs for tunnels for railroads, subways, sewers, water supplies, etc. TBMs employing rotating arrays of drills or hammers were patented. TBMs that resembled giant hole saws were proposed. Other TBMs consisted of a rotating drum with metal tines on its outer surface, or a rotating circular plate covered with teeth, or revolving belts covered with metal teeth. However, these TBMs proved expensive, cumbersome, and unable to excavate hard rock; interest in TBMs therefore declined. Nevertheless, TBM development continued in potash and coal mines, where the rock was softer.
A TBM with a bore diameter of was manufactured by The Robbins Company for Canada's Niagara Tunnel Project. The machine was used to bore a hydroelectric tunnel beneath Niagara Falls. The machine was named "Big Becky" in reference to the Sir Adam Beck hydroelectric dams to which it tunnelled to provide an additional hydroelectric tunnel.
2000s | Tunnel boring machine | Wikipedia | 512 | 577307 | https://en.wikipedia.org/wiki/Tunnel%20boring%20machine | Technology | Transport infrastructure | null |
An earth pressure balance TBM known as Bertha with a bore diameter of was produced by Hitachi Zosen Corporation in 2013. It was delivered to Seattle, Washington, for its Highway 99 tunnel project. The machine began operating in July 2013, but stalled in December 2013 and required substantial repairs that halted the machine until January 2016. Bertha completed boring the tunnel on April 4, 2017.
Two TBMs supplied by CREG excavated two tunnels for Kuala Lumpur's Rapid Transit with a boring diameter of . The medium was water saturated sandy mudstone, schistose mudstone, highly weathered mudstone as well as alluvium. It achieved a maximum advance rate of more than per month.The world's largest hard rock TBM, known as Martina, was built by Herrenknecht AG. Its excavation diameter was , total length ; excavation area of , thrust value 39,485 t, total weight 4,500 tons, total installed capacity 18 MW. Its yearly energy consumption was about 62 GWh. It is owned and operated by the Italian construction company Toto S.p.A. Costruzioni Generali (Toto Group) for the Sparvo gallery of the Italian Motorway Pass A1 ("Variante di Valico A1"), near Florence. The same company built the world's largest-diameter slurry TBM, excavation diameter of , owned and operated by the French construction company Dragages Hong Kong (Bouygues' subsidiary) for the Tuen Mun Chek Lap Kok link in Hong Kong.
Types
TBMs typically consist of a rotating cutting wheel in front, called a cutter head, followed by a main bearing, a thrust system, a system to remove excavated material (muck), and support mechanisms. Machines vary with site geology, amount of ground water present, and other factors.
Rock boring machines differ from earth boring machines in the way they cut the tunnel, the way they provide traction to support the boring activity, and in the way they support the newly formed tunnels walls.
Tunnel wall types
Concrete lining
Shielded TBMs are typically used to excavate tunnels in soil. They erect concrete segments behind the TBM to support the tunnel walls.
The machine stabilizes itself in the tunnel with hydraulic cylinders that press against the shield, allowing the TBM to apply pressure at the tunnel face. | Tunnel boring machine | Wikipedia | 478 | 577307 | https://en.wikipedia.org/wiki/Tunnel%20boring%20machine | Technology | Transport infrastructure | null |
Main Beam
Main Beam machines do not install concrete segments behind the cutter head. Instead, the rock is held up using ground support methods such as ring beams, rock bolts, shotcrete, steel straps, ring steel and wire mesh.
Shield types
Depending on the stability of the local geology, the newly formed walls of the tunnel often need to be supported immediately after being dug to avoid collapse, before any permanent support or lining has been constructed. Many TBMs are equipped with one or more cylindrical shields following behind the cutter head to support the walls until permanent tunnel support is constructed further along the machine. The stability of the walls also influences the method by which the TBM anchors itself in place so that it can apply force to the cutting head. This in turn determines whether the machine can bore and advance simultaneously, or whether these are done in alternating modes.
Open/Gripper
Gripper TBMs are used in rock tunnels. They forgo the use of a shield and instead push directly against the unreinforced sides of the tunnel.
Machines such as a Wirth machine can be moved only while ungripped. Other machines can move continuously. At the end of a Wirth boring cycle, legs drop to the ground, the grippers are retracted, and the machine advances. The grippers then reengage and the rear legs lift for the next cycle.
Single shield
A single-shield TBM has a single cylindrical shield after the cutting head. A permanent concrete lining is constructed immediately after the shield, and the TBM pushes off the lining to apply force to the cutter head. Because this pushing cannot be done while a next ring of lining is being constructed, the single-shield TBM operates in alternating cutting and lining modes.
Double shield
Double Shield (or telescopic shield) TBMs have a leading shield that advances with the cutting head and a trailing shield that acts as a gripper. The two shields can move axially relative to each other (i.e., telescopically) over a limited distance. The gripper shield anchors the TBM so that pressure can be applied to the cutter head while simultaneously the concrete lining is being constructed.
Tunnel-face support methods | Tunnel boring machine | Wikipedia | 443 | 577307 | https://en.wikipedia.org/wiki/Tunnel%20boring%20machine | Technology | Transport infrastructure | null |
In hard rock with minimal ground water, the area around the cutter head of a TBM can be unpressurized, as the exposed rock face can support itself. In weaker soil, or when there is significant ground water, pressure must be applied to the face of the tunnel to prevent collapse and/or the infiltration of ground water into the machine.
Earth Pressure Balance
Earth pressure balance (EPB) machines are used in soft ground with less than of pressure. It uses muck to maintain pressure at the tunnel face. The muck (or spoil) is admitted into the TBM via a screw conveyor. By adjusting the rate of extraction of muck and the advance rate of the TBM, the pressure at the face of the TBM can be controlled without the use of slurry. Additives such as bentonite, polymers and foam can be injected ahead of the face to stabilize the ground. Such additives can separately be injected in the cutter head and extraction screw to ensure that the muck is sufficiently cohesive to maintain pressure and restrict water flow.
Like some other TBM types, EPB's use thrust cylinders to advance by pushing against concrete segments. The cutter head uses a combination of tungsten carbide cutting bits, carbide disc cutters, drag picks and/or hard rock disc cutters.
EPB has allowed soft, wet, or unstable ground to be tunneled with a speed and safety not previously possible. The Channel Tunnel, the Thames Water Ring Main, sections of the London Underground, and most new metro tunnels completed in the last 20 years worldwide were excavated using this method. EPB has historically competed with the slurry shield method (see below), where the slurry is used to stabilize the tunnel face and transport spoil to the surface. EPB TBMs are mostly used in finer ground (such as clay) while slurry TBMs are mostly used for coarser ground (such as gravel).
Slurry shield
Slurry shield machines can be used in soft ground with high water pressure or where granular ground conditions (sands and gravels) do not allow a plug to form in the screw. The cutter head is filled with pressurised slurry, typically made of bentonite clay that applies hydrostatic pressure to the face. The slurry mixes with the muck before it is pumped to a slurry separation plant, usually outside the tunnel. | Tunnel boring machine | Wikipedia | 495 | 577307 | https://en.wikipedia.org/wiki/Tunnel%20boring%20machine | Technology | Transport infrastructure | null |
Slurry separation plants use multi-stage filtration systems that separate spoil from slurry to allow reuse. The degree to which slurry can be 'cleaned' depends on the relative particle sizes of the muck. Slurry TBMs are not suitable for silts and clays as the particle sizes of the spoil are less than that of the bentonite. In this case, water is removed from the slurry leaving a clay cake, which may be polluted.
A caisson system is sometimes placed at the cutting head to allow workers to operate the machine, although air pressure may reach elevated levels in the caisson, requiring workers to be medically cleared as "fit to dive" and able to operate pressure locks.
Open face soft ground
Open face soft ground TBMs rely on the excavated ground to briefly stand without support. They are suitable for use in ground with a strength of up to about with low water inflows. They can bore tunnels with cross-section in excess of . A backactor arm or cutter head bore to within of the edge of the shield. After a boring cycle, the shield is jacked forward to begin a new cycle. Ground support is provided by precast concrete, or occasionally spheroidal graphite iron (SGI) segments that are bolted or supported until a support ring has been added. The final segment, called the key, is wedge-shaped, and expands the ring until it is tight against the ground.
Tunnel size
TBMs range diameter from . Micro tunnel shield TBMs are used to construct small tunnels, and is a smaller equivalent to a general tunnelling shield and generally bore tunnels of , too small for operators to walk in.
Backup systems
Behind all types of tunnel boring machines, in the finished part of the tunnel, are trailing support decks known as the backup system, whose mechanisms can include conveyors or other systems for muck removal; slurry pipelines (if applicable); control rooms; electrical, dust-removal and ventilation systems; and mechanisms for transport of pre-cast segments.
Urban tunnelling and near-surface tunnelling
Urban tunnelling has the special requirement that the surface remain undisturbed, and that ground subsidence be avoided. The normal method of doing this in soft ground is to maintain soil pressures during and after construction. | Tunnel boring machine | Wikipedia | 473 | 577307 | https://en.wikipedia.org/wiki/Tunnel%20boring%20machine | Technology | Transport infrastructure | null |
TBMs with positive face control, such as earth pressure balance (EPB) and slurry shield (SS), are used in such situations. Both types (EPB and SS) are capable of reducing the risk of surface subsidence and voids if ground conditions are well documented. When tunnelling in urban environments, other tunnels, existing utility lines and deep foundations must be considered, and the project must accommodate measures to mitigate any detrimental effects to other infrastructure. | Tunnel boring machine | Wikipedia | 96 | 577307 | https://en.wikipedia.org/wiki/Tunnel%20boring%20machine | Technology | Transport infrastructure | null |
An extraterrestrial vortex is a vortex that occurs on planets and natural satellites other than Earth that have sufficient atmospheres. Most observed extraterrestrial vortices have been seen in large cyclones, or anticyclones. However, occasional dust storms have been known to produce vortices on Mars and Titan. Various spacecraft missions have recorded evidence of past and present extraterrestrial vortices. The largest extraterrestrial vortices are found on the gas giants, Jupiter and Saturn; and the ice giants, Uranus and Neptune.
Mercury
Due to Mercury's thin atmosphere, it does not experience weather-like storms or other atmospheric weather phenomena such as clouds, winds, or rain. Rather unusually, Mercury has magnetic 'tornadoes' that were observed by NASA's Mercury MESSENGER during a flyby in 2008. The tornadoes are twisted bundles of magnetic fields that connect Mercury's magnetic field to space.
Venus
Venus Express observed two large shape-shifting vortices on Venus' poles (polar vortices) in 2006 on one of its close-up flybys of the planet. The south pole was seen to have a large, constantly changing, double-eye vortex through high-resolution infrared measurements obtained by the VIRTIS instrument on Venus Express. The cause of the double-eyed vortex is unknown but the polar vortices are caused by the Hadley Cell atmospheric circulation of the lower atmosphere. Unusually, neither of the double vortices at the south pole ever line up and are located at slightly different altitudes. The southern pole's cyclone-like storm is roughly the size of Europe. In addition, the southern polar vortex is constantly changing shape but the cause is still unknown.
In 1979, NASA's Pioneer Venus observed a double vortex cyclone at the north pole. There have not been many more close-up observations of the north pole since Pioneer Venus.
Since most of the planet's water has escaped to space, Venus does not experience rain like Earth does. However, there has been evidence of lightning on Venus as confirmed by data from Venus Express. The lightning on Venus is different than the lightning on all other planets as it is associated with sulfuric acid clouds instead of water clouds. The magnetometer instrument on Venus Express detected electrical discharges when the spacecraft was orbiting close to the upper atmosphere of Venus. Most storms form high up in the atmosphere about 25 miles from the surface and all precipitation evaporates about 20 miles above the surface.
Mars | Extraterrestrial vortex | Wikipedia | 501 | 8644994 | https://en.wikipedia.org/wiki/Extraterrestrial%20vortex | Physical sciences | Planetary science | Astronomy |
Most of the observed atmospheric events on Mars are dust storms which can sometimes disrupt enough dust to be seen from Earth. Many large dust storms occur every year on Mars but even more rare are the global dust storms that Mars experiences on average every 6 Earth years. NASA has observed global dust storms in 1971, 1977, 1982, 1994, 2001, 2007, and 2018. While these massive dust storms do cause problems for rovers and spacecraft operating on solar power, the winds on Mars top out at , less than half as strong as hurricane-force winds on Earth, which is not enough to rip apart mechanical equipment.
While Mars is most known for its recurring dust storms, it still experiences cyclone-like storms and polar vortices similar to Earth.
On April 27, 1999, a rare cyclone in diameter was detected by the Hubble Space Telescope in the northern polar region of Mars. It consisted of three cloud bands wrapped around a massive diameter eye, and contained features similar to storms that have been detected in the poles of Earth (see: polar low). It was only observed briefly, as it seemed to be dissipating when it was imaged six hours later, and was not seen on later imaging passes. Several other cyclones were imaged in about the same area: the March 2, 2001 cyclone, January 19, 2003 cyclone, and the November 27, 2004 cyclone.
In addition, NASA's 2001 Mars Odyssey Spacecraft observed a cold, low density, polar vortex in the planet's atmosphere above latitudes 70 degrees north and higher. NASA determined that every winter a polar vortex forms over the north pole above the atmosphere. The vortex and atmosphere are separated by a transition zone where strong winds encircle the pole and terrestrial jet stream-like characteristics. The stability of these annular polar vortices are still being researched as scientists believe Martian dust may play a role in their formation.
Jupiter
Jupiter's atmosphere is lined with hundreds of vortices most likely to be cyclones, or anticyclones, similar to those on Earth. Voyager and Cassini discovered that, unlike the terrestrial atmosphere, 90% of Jovian vortices are anticyclones, meaning they rotate in the opposite direction of the planet's rotation. Many cyclones have showed up and disappeared over the years with some even merging to form larger cyclones. | Extraterrestrial vortex | Wikipedia | 470 | 8644994 | https://en.wikipedia.org/wiki/Extraterrestrial%20vortex | Physical sciences | Planetary science | Astronomy |
When NASA's Juno Spacecraft arrived at Jupiter in 2016, it observed giant cyclones encircling the north and south poles of the planet. Nine large cyclones were spotted around the north pole and 6 around the south pole. Upon further flybys, Juno spotted another cyclone at the south pole and noticed that 6 of the 7 cyclones formed a hexagonal arrangement around the cyclone at the center of the south pole. Data from Juno has shown that this storm system is stable and there have been no signs of vortices attempting to merge.
The Great Red Spot on Jupiter is, by far, the largest extraterrestrial anticyclone (or cyclone) known. The Great Red Spot is located in the southern hemisphere and has wind speeds greater than any storm ever measured on Earth. New data from Juno found that the storm penetrates into Jupiter's atmosphere about . The giant storm has been monitored since 1830 but has possibly survived for over 350 years. Over 100 years ago, the Great Red Spot was well over two Earths wide but has been shrinking ever since. When Voyagers 1 and 2 flew by in 1979, they measured the massive cyclone to be twice Earth's diameter. Measurements today from telescopes have measured a diameter of 1.3 Earths wide.
Oval BA (or Red Spot Jr.) is the second-largest storm on Jupiter and formed from the merging of 3 smaller cyclones in 2000. It is located just to the south of the Great Red Spot and has been increasing in size in recent years, slowly turning a more uniform white.
The Great Dark Spot is a feature observed near Jupiter's north pole in 2000 by the Cassini–Huygens spacecraft that was a short-lived dark cloud that grew to the size of the Great Red Spot before disappearing after 11 weeks. The phenomenon is speculated by scientists to be a side-effect of strong auroras on Jupiter.
Saturn
Every Saturn year, about 28 Earth years, Saturn has massive planet-circling storms, called Great White Spots. The Great White Spots are short-lived but can impact the atmosphere and temperature of the planet for up to 3 Earth years after their collapse. The spots can be several thousand kilometers wide and can even run into their own tails and fade out once they circle the planet. | Extraterrestrial vortex | Wikipedia | 458 | 8644994 | https://en.wikipedia.org/wiki/Extraterrestrial%20vortex | Physical sciences | Planetary science | Astronomy |
Most storms on Saturn occur in a zone in the southern hemisphere dubbed 'storm alley' by scientists for its high abundance of storm activity. Storm alley lies 35 degrees south of the equator and it is still unknown why there is such a large quantity of storms that form here. There is also a long-lived storm known as the Dragon Storm, which flares occasionally on Saturn's southern latitudes. Cassini detected bursts of radio emissions from the storm on multiple occasions, similar to the short bursts of static that are produced from lightning on earth.
On October 11, 2006, the Cassini-Huygens spacecraft took images of a storm with a well-defined distinct eyewall over the south pole of Saturn. It was across, with storms in the eyewall reaching high. The storm had wind speeds of and appeared to be stationary over Saturn's south pole.
Saturn currently holds the record for the longest continuous thunderstorm in the Solar System with a storm that Cassini observed back in 2009 that lasted for over 8 months. Instruments on Cassini detected powerful radio waves coming from lightning discharges in Saturn's atmosphere. These radio waves are about 10,000 times stronger than the ones emitted by terrestrial lightning.
A hexagonal cyclone in Saturn's north pole has been spotted since the passage of Voyager 1 and 2, and was first imaged by Cassini on January 3, 2009. It is just under in diameter, with a depth of about , and encircles the north pole of the ringed planet at roughly 78° N latitude.
Titan
Titan is very similar to Earth and is the only known planetary body with a substantial atmosphere and stable bodies of surface liquid that still exist. Titan experiences storms similar to Earth, but instead of water there is methane and ethane liquids on Titan.
Data from Cassini found that Titan experiences dust storms similar to those on Earth and Mars. When Titan is in equinox, strong down-burst winds raise micron-sized particles up from sand dunes and create dust storms. The dust storms are relatively short but create intense infrared bright spots in the atmosphere, which is how Cassini detected them.
Cassini captured an image of a south polar vortex on Titan in June 2012. Titan was also found to have a northern polar vortex with similar characteristics as the southern polar vortex. Scientists later found that these vortices formed during the winter, meaning they were seasonal, similar to Earth's polar vortices. | Extraterrestrial vortex | Wikipedia | 495 | 8644994 | https://en.wikipedia.org/wiki/Extraterrestrial%20vortex | Physical sciences | Planetary science | Astronomy |
The south polar vortex was imaged again in 2013 and it was determined that the vortex forms higher up in the atmosphere than previously thought. The hazy atmosphere that Titan has leaves the moon unilluminated in the Sun's rays but the image of the vortex showed a bright spot on the south pole. Scientists derived that the vortex is high up in the atmosphere, possibly above the haze, because it can still be illuminated by the Sun.
Uranus
Uranus was long thought to be atmospherically static due to the lack of storms observed, but in recent years astronomers have started to see more storm activity on the planet. However, there is still limited data on Uranus as it is so far away from Earth and hard to observe regularly.
In 2018, Hubble Space Telescope (HST) captured an image of Uranus that showed a large, bright, polar cap over the north pole. The storm is thought to be long-lived and scientists hypothesize it formed by seasonal changes in atmospheric flow.
In 2006, Hubble Space Telescope imaged the Uranus Dark Spot. Scientists saw similarities between the Uranus Dark Spot (UDS) and the Great Dark Spots (GDS) on Neptune, although UDS was much smaller. GDS were thought to be anticyclonic vortices in Neptune's atmosphere and UDS is assumed to be similar in nature.
In 1998, HST captured infrared images of multiple storms raging on Uranus due to seasonal changes.
Neptune
The Great Dark Spot was an Earth-sized vortex observed in the southern hemisphere of Neptune by Voyager 2 in 1989. The storm had some of the highest recorded wind speeds in the Solar System at approximately and rotated around the planet once every 18.3 hours. When the Hubble Space Telescope turned its gaze to Neptune in 1994, the spot had vanished; but the storm causing the spot might have continued lower in the atmosphere.
The Small Dark Spot (sometimes called Great Dark Spot 2 or Wizard's Eye) was another vortex observed by Voyager 2 in its 1989 pass of Neptune. This spot is located approximately 30° further south on the planet and transits the planet once every 16.1 hours. The Small Dark Spot's distinct appearance comes from white methane-ice clouds which upwell through the center of the storm and give it an eye-like appearance. This storm had also apparently vanished by the time the Hubble Space Telescope inspected the planet in 1994. | Extraterrestrial vortex | Wikipedia | 493 | 8644994 | https://en.wikipedia.org/wiki/Extraterrestrial%20vortex | Physical sciences | Planetary science | Astronomy |
A total of 4 additional dark spots have been observed on Neptune since the discovery of the first two. A small storm which formed in the southern hemisphere in 2015 was tracked by Amy Simon and her team at NASA Goddard (she is now part of the Outer Planet Atmospheres Legacy project) from its birth to its death. While focused on tracking this small storm the team was able to discover the emergence of a giant spot the size of the Great Dark Spot at 23° North of the equator in 2018. The observations taken by this team were able to point to the importance of "companion clouds" in identifying the storms that cause these spots even while a dark spot was not present. This team also concluded that the storms have a likely lifespan of 2 years with a life of up to 6 years being possible, and will look to study the shape and speed of dark spots in the future. | Extraterrestrial vortex | Wikipedia | 175 | 8644994 | https://en.wikipedia.org/wiki/Extraterrestrial%20vortex | Physical sciences | Planetary science | Astronomy |
Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles either have their origins in soil and rocks and have been transported from the land to the sea, mainly by rivers but also by dust carried by wind and by the flow of glaciers into the sea, or they are biogenic deposits from marine organisms or from chemical precipitation in seawater, as well as from underwater volcanoes and meteorite debris.
Except within a few kilometres of a mid-ocean ridge, where the volcanic rock is still relatively young, most parts of the seafloor are covered in sediment. This material comes from several different sources and is highly variable in composition. Seafloor sediment can range in thickness from a few millimetres to several tens of kilometres. Near the surface seafloor sediment remains unconsolidated, but at depths of hundreds to thousands of metres the sediment becomes lithified (turned to rock).
Rates of sediment accumulation are relatively slow throughout most of the ocean, in many cases taking thousands of years for any significant deposits to form. Sediment transported from the land accumulates the fastest, on the order of one metre or more per thousand years for coarser particles. However, sedimentation rates near the mouths of large rivers with high discharge can be orders of magnitude higher. Biogenous oozes accumulate at a rate of about one centimetre per thousand years, while small clay particles are deposited in the deep ocean at around one millimetre per thousand years.
Sediments from the land are deposited on the continental margins by surface runoff, river discharge, and other processes. Turbidity currents can transport this sediment down the continental slope to the deep ocean floor. The deep ocean floor undergoes its own process of spreading out from the mid-ocean ridge, and then slowly subducts accumulated sediment on the deep floor into the molten interior of the earth. In turn, molten material from the interior returns to the surface of the earth in the form of lava flows and emissions from deep sea hydrothermal vents, ensuring the process continues indefinitely. The sediments provide habitat for a multitude of marine life, particularly of marine microorganisms. Their fossilized remains contain information about past climates, plate tectonics, ocean circulation patterns, and the timing of major extinctions. | Marine sediment | Wikipedia | 473 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Overview
Except within a few kilometres of a mid-ocean ridge, where the volcanic rock is still relatively young, most parts of the seafloor are covered in sediments. This material comes from several different sources and is highly variable in composition, depending on proximity to a continent, water depth, ocean currents, biological activity, and climate. Seafloor sediments (and sedimentary rocks) can range in thickness from a few millimetres to several tens of kilometres. Near the surface, the sea-floor sediments remain unconsolidated, but at depths of hundreds to thousands of metres (depending on the type of sediment and other factors) the sediment becomes lithified.
The various sources of seafloor sediment can be summarized as follows:
Terrigenous sediment is derived from continental sources transported by rivers, wind, ocean currents, and glaciers. It is dominated by quartz, feldspar, clay minerals, iron oxides, and terrestrial organic matter.
Pelagic carbonate sediment is derived from organisms (e.g., foraminifera) living in the ocean water (at various depths, but mostly near surface) that make their shells (a.k.a. tests) out of carbonate minerals such as calcite.
Pelagic silica sediment is derived from marine organisms (e.g., diatoms and radiolaria) that make their tests out of silica (microcrystalline quartz).
Volcanic ash and other volcanic materials are derived from both terrestrial and submarine eruptions.
Iron and manganese nodules form as direct precipitates from ocean-bottom water. | Marine sediment | Wikipedia | 323 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
The distributions of some of these materials around the seas are shown in the diagram at the start of this article ↑. Terrigenous sediments predominate near the continents and within inland seas and large lakes. These sediments tend to be relatively coarse, typically containing sand and silt, but in some cases even pebbles and cobbles. Clay settles slowly in nearshore environments, but much of the clay is dispersed far from its source areas by ocean currents. Clay minerals are predominant over wide areas in the deepest parts of the ocean, and most of this clay is terrestrial in origin. Siliceous oozes (derived from radiolaria and diatoms) are common in the south polar region, along the equator in the Pacific, south of the Aleutian Islands, and within large parts of the Indian Ocean. Carbonate oozes are widely distributed in all of the oceans within equatorial and mid-latitude regions. In fact, clay settles everywhere in the oceans, but in areas where silica- and carbonate-producing organisms are prolific, they produce enough silica or carbonate sediment to dominate over clay.
Carbonate sediments are derived from a wide range of near-surface pelagic organisms that make their shells out of carbonate. These tiny shells, and the even tinier fragments that form when they break into pieces, settle slowly through the water column, but they don't necessarily make it to the bottom. While calcite is insoluble in surface water, its solubility increases with depth (and pressure) and at around 4,000 m, the carbonate fragments dissolve. This depth, which varies with latitude and water temperature, is known as the carbonate compensation depth. As a result, carbonate oozes are absent from the deepest parts of the ocean (deeper than 4,000 m), but they are common in shallower areas such as the mid-Atlantic ridge, the East Pacific Rise (west of South America), along the trend of the Hawaiian/Emperor Seamounts (in the northern Pacific), and on the tops of many isolated seamounts.
Texture | Marine sediment | Wikipedia | 421 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Sediment texture can be examined in several ways. The first way is grain size. Sediments can be classified by particle size according to the Wentworth scale. Clay sediments are the finest with a grain diameter of less than .004 mm and boulders are the largest with grain diameters of 256 mm or larger. Among other things, grain size represents the conditions under which the sediment was deposited. High energy conditions, such as strong currents or waves, usually results in the deposition of only the larger particles as the finer ones will be carried away. Lower energy conditions will allow the smaller particles to settle out and form finer sediments.
Sorting is another way to categorize sediment texture. Sorting refers to how uniform the particles are in terms of size. If all of the particles are of a similar size, such as in beach sand, the sediment is well-sorted. If the particles are of very different sizes, the sediment is poorly sorted, such as in glacial deposits.
A third way to describe marine sediment texture is its maturity, or how long its particles have been transported by water. One way which can indicate maturity is how round the particles are. The more mature a sediment the rounder the particles will be, as a result of being abraded over time. A high degree of sorting can also indicate maturity, because over time the smaller particles will be washed away, and a given amount of energy will move particles of a similar size over the same distance. Lastly, the older and more mature a sediment the higher the quartz content, at least in sediments derived from rock particles. Quartz is a common mineral in terrestrial rocks, and it is very hard and resistant to abrasion. Over time, particles made from other materials are worn away, leaving only quartz behind. Beach sand is a very mature sediment; it is composed primarily of quartz, and the particles are rounded and of similar size (well-sorted).
Origins
Marine sediments can also classified by their source of origin. There are four types: | Marine sediment | Wikipedia | 399 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Lithogenous sediments, also called terrigenous sediments, are derived from preexisting rock and come from land via rivers, ice, wind and other processes. They are referred to as terrigenous sediments since most comes from the land.
Biogenous sediments are composed of the remains of marine organisms, and come from organisms like plankton when their exoskeletons break down
Hydrogenous sediments come from chemical reactions in the water, and are formed when materials that are dissolved in water precipitate out and form solid particles.
Cosmogenous sediments are derived from extraterrestrial sources, coming from space, filtering in through the atmosphere or carried to Earth on meteorites.
Lithogenous
Lithogenous or terrigenous sediment is primarily composed of small fragments of preexisting rocks that have made their way into the ocean. These sediments can contain the entire range of particle sizes, from microscopic clays to large boulders, and they are found almost everywhere on the ocean floor. Lithogenous sediments are created on land through the process of weathering, where rocks and minerals are broken down into smaller particles through the action of wind, rain, water flow, temperature- or ice-induced cracking, and other erosive processes. These small eroded particles are then transported to the oceans through a variety of mechanisms:
Streams and rivers: Various forms of runoff deposit large amounts of sediment into the oceans, mostly in the form of finer-grained particles. About 90% of the lithogenous sediment in the oceans is thought to have come from river discharge, particularly from Asia. Most of this sediment, especially the larger particles, will be deposited and remain fairly close to the coastline, however, smaller clay particles may remain suspended in the water column for long periods of time and may be transported great distances from the source.
Wind: Windborne (aeolian) transport can take small particles of sand and dust and move them thousands of kilometres from the source. These small particles can fall into the ocean when the wind dies down, or can serve as the nuclei around which raindrops or snowflakes form. Aeolian transport is particularly important near desert areas. | Marine sediment | Wikipedia | 446 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Glaciers and ice rafting: As glaciers grind their way over land, they pick up lots of soil and rock particles, including very large boulders, that get carried by the ice. When the glacier meets the ocean and begins to break apart or melt, these particles get deposited. Most of the deposition will happen close to where the glacier meets the water, but a small amount of material is also transported longer distances by rafting, where larger pieces of ice drift far from the glacier before releasing their sediment.
Gravity: Landslides, mudslides, avalanches, and other gravity-driven events can deposit large amounts of material into the ocean when they happen close to shore.
Waves: Wave action along a coastline will erode rocks and will pull loose particles from beaches and shorelines into the water.
Volcanoes: Volcanic eruptions emit vast amounts of ash and other debris into the atmosphere, where it can then be transported by wind to eventually get deposited in the oceans.
Gastroliths: Another, relatively minor, means of transporting lithogenous sediment to the ocean are gastroliths. Gastrolith means "stomach stone". Many animals, including seabirds, pinnipeds, and some crocodiles deliberately swallow stones and regurgitate them latter. Stones swallowed on land can be regurgitated at sea. The stones can help grind food in the stomach or act as ballast regulating buoyancy. Mostly these processes deposit lithogenous sediment close to shore. Sediment particles can then be transported farther by waves and currents, and may eventually escape the continental shelf and reach the deep ocean floor.
Composition
Lithogenous sediments usually reflect the composition of whatever materials they were derived from, so they are dominated by the major minerals that make up most terrestrial rock. This includes quartz, feldspar, clay minerals, iron oxides, and terrestrial organic matter. Quartz (silicon dioxide, the main component of glass) is one of the most common minerals found in nearly all rocks, and it is very resistant to abrasion, so it is a dominant component of lithogenous sediments, including sand.
Biogenous
Biogenous sediments come from the remains of living organisms that settle out as sediment when the organisms die. It is the "hard parts" of the organisms that contribute to the sediments; things like shells, teeth or skeletal elements, as these parts are usually mineralized and are more resistant to decomposition than the fleshy "soft parts" that rapidly deteriorate after death. | Marine sediment | Wikipedia | 505 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Macroscopic sediments contain large remains, such as skeletons, teeth, or shells of larger organisms. This type of sediment is fairly rare over most of the ocean, as large organisms do not die in enough of a concentrated abundance to allow these remains to accumulate. One exception is around coral reefs; here there is a great abundance of organisms that leave behind their remains, in particular the fragments of the stony skeletons of corals that make up a large percentage of tropical sand.
Microscopic sediment consists of the hard parts of microscopic organisms, particularly their shells, or tests. Although very small, these organisms are highly abundant and as they die by the billions every day their tests sink to the bottom to create biogenous sediments. Sediments composed of microscopic tests are far more abundant than sediments from macroscopic particles, and because of their small size they create fine-grained, mushy sediment layers. If the sediment layer consists of at least 30% microscopic biogenous material, it is classified as a biogenous ooze. The remainder of the sediment is often made up of clay.
The primary sources of microscopic biogenous sediments are unicellular algaes and protozoans (single-celled amoeba-like creatures) that secrete tests of either calcium carbonate (CaCO3) or silica (SiO2). Silica tests come from two main groups, the diatoms (algae) and the radiolarians (protozoans).
Diatoms are particularly important members of the phytoplankton, functioning as small, drifting algal photosynthesizers. A diatom consists of a single algal cell surrounded by an elaborate silica shell that it secretes for itself. Diatoms come in a range of shapes, from elongated, pennate forms, to round, or centric shapes that often have two halves, like a Petri dish. In areas where diatoms are abundant, the underlying sediment is rich in silica diatom tests, and is called diatomaceous earth. | Marine sediment | Wikipedia | 416 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Radiolarians are planktonic protozoans (making them part of the zooplankton), that like diatoms, secrete a silica test. The test surrounds the cell and can include an array of small openings through which the radiolarian can extend an amoeba-like "arm" or pseudopod. Radiolarian tests often display a number of rays protruding from their shells which aid in buoyancy. Oozes that are dominated by diatom or radiolarian tests are called siliceous oozes.
Like the siliceous sediments, the calcium carbonate, or calcareous sediments are also produced from the tests of microscopic algae and protozoans; in this case the coccolithophores and foraminiferans. Coccolithophores are single-celled planktonic algae about 100 times smaller than diatoms. Their tests are composed of a number of interlocking CaCO3 plates (coccoliths) that form a sphere surrounding the cell. When coccolithophores die the individual plates sink out and form an ooze. Over time, the coccolithophore ooze lithifies to becomes chalk. The White Cliffs of Dover in England are composed of coccolithophore-rich ooze that turned into chalk deposits.
Foraminiferans (also referred to as forams) are protozoans whose tests are often chambered, similar to the shells of snails. As the organism grows, is secretes new, larger chambers in which to reside. Most foraminiferans are benthic, living on or in the sediment, but there are some planktonic species living higher in the water column. When coccolithophores and foraminiferans die, they form calcareous oozes.
Older calcareous sediment layers contain the remains of another type of organism, the discoasters; single-celled algae related to the coccolithophores that also produced calcium carbonate tests. Discoaster tests were star-shaped, and reached sizes of 5-40 μm across. Discoasters went extinct approximately 2 million years ago, but their tests remain in deep, tropical sediments that predate their extinction. | Marine sediment | Wikipedia | 466 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Because of their small size, these tests sink very slowly; a single microscopic test may take about 10–50 years to sink to the bottom! Given that slow descent, a current of only 1 cm/sec could carry the test as much as 15,000 km away from its point of origin before it reaches the bottom. Despite this, the sediments in a particular location are well-matched to the types of organisms and degree of productivity that occurs in the water overhead. This means the sediment particles must be sinking to the bottom at a much faster rate, so they accumulate below their point of origin before the currents can disperse them. Most of the tests do not sink as individual particles; about 99% of them are first consumed by some other organism, and are then aggregated and expelled as large fecal pellets, which sink much more quickly and reach the ocean floor in only 10–15 days. This does not give the particles as much time to disperse, and the sediment below will reflect the production occurring near the surface. The increased rate of sinking through this mechanism has been called the "fecal express".
Hydrogenous
Seawater contains many different dissolved substances. Occasionally chemical reactions occur that cause these substances to precipitate out as solid particles, which then accumulate as hydrogenous sediment. These reactions are usually triggered by a change in conditions, such as a change in temperature, pressure, or pH, which reduces the amount of a substance that can remain in a dissolved state. There is not a lot of hydrogenous sediment in the ocean compared to lithogenous or biogenous sediments, but there are some interesting forms.
In hydrothermal vents seawater percolates into the seafloor where it becomes superheated by magma before being expelled by the vent. This superheated water contains many dissolved substances, and when it encounters the cold seawater after leaving the vent, these particles precipitate out, mostly as metal sulfides. These particles make up the "smoke" that flows from a vent, and may eventually settle on the bottom as hydrogenous sediment. Hydrothermal vents are distributed along the Earth's plate boundaries, although they may also be found at intra-plate locations such as hotspot volcanoes. Currently there are about 500 known active submarine hydrothermal vent fields, about half visually observed at the seafloor and the other half suspected from water column indicators and/or seafloor deposits. | Marine sediment | Wikipedia | 493 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Manganese nodules are rounded lumps of manganese and other metals that form on the seafloor, generally ranging between 3–10 cm in diameter, although they may sometimes reach up to 30 cm. The nodules form in a manner similar to pearls; there is a central object around which concentric layers are slowly deposited, causing the nodule to grow over time. The composition of the nodules can vary somewhat depending on their location and the conditions of their formation, but they are usually dominated by manganese- and iron oxides. They may also contain smaller amounts of other metals such as copper, nickel and cobalt. The precipitation of manganese nodules is one of the slowest geological processes known; they grow on the order of a few millimetres per million years. For that reason, they only form in areas where there are low rates of lithogenous or biogenous sediment accumulation, because any other sediment deposition would quickly cover the nodules and prevent further nodule growth. Therefore, manganese nodules are usually limited to areas in the central ocean, far from significant lithogenous or biogenous inputs, where they can sometimes accumulate in large numbers on the seafloor (Figure 12.4.2 right). Because the nodules contain a number of commercially valuable metals, there has been significant interest in mining the nodules over the last several decades, although most of the efforts have thus far remained at the exploratory stage. A number of factors have prevented large-scale extraction of nodules, including the high costs of deep sea mining operations, political issues over mining rights, and environmental concerns surrounding the extraction of these non-renewable resources. | Marine sediment | Wikipedia | 341 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Evaporites are hydrogenous sediments that form when seawater evaporates, leaving the dissolved materials to precipitate into solids, particularly halite (salt, NaCl). In fact, the evaporation of seawater is the oldest form of salt production for human use, and is still carried out today. Large deposits of halite evaporites exist in a number of places, including under the Mediterranean Sea. Beginning around 6 million years ago, tectonic processes closed off the Mediterranean Sea from the Atlantic, and the warm climate evaporated so much water that the Mediterranean was almost completely dried out, leaving large deposits of salt in its place (an event known as the Messinian Salinity Crisis). Eventually the Mediterranean re-flooded about 5.3 million years ago, and the halite deposits were covered by other sediments, but they still remain beneath the seafloor.
Oolites are small, rounded grains formed from concentric layers of precipitation of material around a suspended particle. They are usually composed of calcium carbonate, but they may also from phosphates and other materials. Accumulation of oolites results in oolitic sand, which is found in its greatest abundance in the Bahamas. | Marine sediment | Wikipedia | 247 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Methane hydrates are another type of hydrogenous deposit with a potential industrial application. All terrestrial erosion products include a small proportion of organic matter derived mostly from terrestrial plants. Tiny fragments of this material plus other organic matter from marine plants and animals accumulate in terrigenous sediments, especially within a few hundred kilometres of shore. As the sediments pile up, the deeper parts start to warm up (from geothermal heat), and bacteria get to work breaking down the contained organic matter. Because this is happening in the absence of oxygen (a.k.a. anaerobic conditions), the by-product of this metabolism is the gas methane (CH4). Methane released by the bacteria slowly bubbles upward through the sediment toward the seafloor. At water depths of 500 m to 1,000 m, and at the low temperatures typical of the seafloor (close to 4 °C), water and methane combine to create a substance known as methane hydrate. Within a few metres to hundreds of metres of the seafloor, the temperature is low enough for methane hydrate to be stable and hydrates accumulate within the sediment. Methane hydrate is flammable because when it is heated, the methane is released as a gas. The methane within seafloor sediments represents an enormous reservoir of fossil fuel energy. Although energy corporations and governments are anxious to develop ways to produce and sell this methane, anyone that understands the climate-change implications of its extraction and use can see that this would be folly.
Cosmogenous
Cosmogenous sediment is derived from extraterrestrial sources, and comes in two primary forms; microscopic spherules and larger meteor debris. Spherules are composed mostly of silica or iron and nickel, and are thought to be ejected as meteors burn up after entering the atmosphere. Meteor debris comes from collisions of meteorites with Earth. These high impact collisions eject particles into the atmosphere that eventually settle back down to Earth and contribute to the sediments. Like spherules, meteor debris is mostly silica or iron and nickel. One form of debris from these collisions are tektites, which are small droplets of glass. They are likely composed of terrestrial silica that was ejected and melted during a meteorite impact, which then solidified as it cooled upon returning to the surface. | Marine sediment | Wikipedia | 468 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Cosmogenous sediment is fairly rare in the ocean and it does not usually accumulate in large deposits. However, it is constantly being added to through space dust that continuously rains down on Earth. About 90% of incoming cosmogenous debris is vaporized as it enters the atmosphere, but it is estimated that 5 to 300 tons of space dust land on the Earth's surface each day.
Composition
Siliceous ooze
Siliceous ooze is a type of biogenic pelagic sediment located on the deep ocean floor. Siliceous oozes are the least common of the deep sea sediments, and make up approximately 15% of the ocean floor. Oozes are defined as sediments which contain at least 30% skeletal remains of pelagic microorganisms. Siliceous oozes are largely composed of the silica based skeletons of microscopic marine organisms such as diatoms and radiolarians. Other components of siliceous oozes near continental margins may include terrestrially derived silica particles and sponge spicules. Siliceous oozes are composed of skeletons made from opal silica Si(O2), as opposed to calcareous oozes, which are made from skeletons of calcium carbonate organisms (i.e. coccolithophores). Silica (Si) is a bioessential element and is efficiently recycled in the marine environment through the silica cycle. Distance from land masses, water depth and ocean fertility are all factors that affect the opal silica content in seawater and the presence of siliceous oozes.
Calcareous ooze | Marine sediment | Wikipedia | 336 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
The term calcareous can be applied to a fossil, sediment, or sedimentary rock which is formed from, or contains a high proportion of, calcium carbonate in the form of calcite or aragonite. Calcareous sediments (limestone) are usually deposited in shallow water near land, since the carbonate is precipitated by marine organisms that need land-derived nutrients. Generally speaking, the farther from land sediments fall, the less calcareous they are. Some areas can have interbedded calcareous sediments due to storms, or changes in ocean currents. Calcareous ooze is a form of calcium carbonate derived from planktonic organisms that accumulates on the sea floor. This can only occur if the ocean is shallower than the carbonate compensation depth. Below this depth, calcium carbonate begins to dissolve in the ocean, and only non-calcareous sediments are stable, such as siliceous ooze or pelagic red clay.
Lithified sediments
Distribution
Where and how sediments accumulate will depend on the amount of material coming from a source, the distance from the source, the amount of time that sediment has had to accumulate, how well the sediments are preserved, and the amounts of other types of sediments that are also being added to the system.
Rates of sediment accumulation are relatively slow throughout most of the ocean, in many cases taking thousands of years for any significant deposits to form. Lithogenous sediment accumulates the fastest, on the order of one metre or more per thousand years for coarser particles. However, sedimentation rates near the mouths of large rivers with high discharge can be orders of magnitude higher.
Biogenous oozes accumulate at a rate of about 1 cm per thousand years, while small clay particles are deposited in the deep ocean at around one millimetre per thousand years. As described above, manganese nodules have an incredibly slow rate of accumulation, gaining 0.001 millimetres per thousand years.
Marine sediments are thickest near the continental margins where they can be over 10 km thick. This is because the crust near passive continental margins is often very old, allowing for a long period of accumulation, and because there is a large amount of terrigenous sediment input coming from the continents. Near mid-ocean ridge systems where new oceanic crust is being formed, sediments are thinner, as they have had less time to accumulate on the younger crust. | Marine sediment | Wikipedia | 483 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
As distance increases from a ridge spreading center the sediments get progressively thicker, increasing by approximately 100–200 m of sediment for every 1000 km distance from the ridge axis. With a seafloor spreading rate of about 20–40 km/million years, this represents a sediment accumulation rate of approximately 100–200 m every 25–50 million years.
The diagram at the start of this article ↑ shows the distribution of the major types of sediment on the ocean floor. Cosmogenous sediments could potentially end up in any part of the ocean, but they accumulate in such small abundances that they are overwhelmed by other sediment types and thus are not dominant in any location. Similarly, hydrogenous sediments can have high concentrations in specific locations, but these regions are very small on a global scale. So cosmogenous and hydrogenous sediments can mostly be ignored in the discussion of global sediment patterns.
Coarse lithogenous/terrigenous sediments are dominant near the continental margins as land runoff, river discharge, and other processes deposit vast amounts of these materials on the continental shelf. Much of this sediment remains on or near the shelf, while turbidity currents can transport material down the continental slope to the deep ocean floor (abyssal plain). Lithogenous sediment is also common at the poles where thick ice cover can limit primary production, and glacial breakup deposits sediments along the ice edge.
Coarse lithogenous sediments are less common in the central ocean, as these areas are too far from the sources for these sediments to accumulate. Very small clay particles are the exception, and as described below, they can accumulate in areas that other lithogenous sediment will not reach.
The distribution of biogenous sediments depends on their rates of production, dissolution, and dilution by other sediments. Coastal areas display very high primary production, so abundant biogenous deposits might be expected in these regions. However, sediment must be >30% biogenous to be considered a biogenous ooze, and even in productive coastal areas there is so much lithogenous input that it swamps the biogenous materials, and that 30% threshold is not reached. So coastal areas remain dominated by lithogenous sediment, and biogenous sediments will be more abundant in pelagic environments where there is little lithogenous input. | Marine sediment | Wikipedia | 473 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
In order for biogenous sediments to accumulate their rate of production must be greater than the rate at which the tests dissolve. Silica is undersaturated throughout the ocean and will dissolve in seawater, but it dissolves more readily in warmer water and lower pressures; that is, it dissolves faster near the surface than in deep water. Silica sediments will therefore only accumulate in cooler regions of high productivity where they accumulate faster than they dissolve. This includes upwelling regions near the equator and at high latitudes where there are abundant nutrients and cooler water.
Oozes formed near the equatorial regions are usually dominated by radiolarians, while diatoms are more common in the polar oozes. Once the silica tests have settled on the bottom and are covered by subsequent layers, they are no longer subject to dissolution and the sediment will accumulate. Approximately 15% of the seafloor is covered by siliceous oozes.
Biogenous calcium carbonate sediments also require production to exceed dissolution for sediments to accumulate, but the processes involved are a little different than for silica. Calcium carbonate dissolves more readily in more acidic water. Cold seawater contains more dissolved CO2 and is slightly more acidic than warmer water. So calcium carbonate tests are more likely to dissolve in colder, deeper, polar water than in warmer, tropical, surface water. At the poles the water is uniformly cold, so calcium carbonate readily dissolves at all depths, and carbonate sediments do not accumulate. In temperate and tropical regions calcium carbonate dissolves more readily as it sinks into deeper water.
The depth at which calcium carbonate dissolves as fast as it accumulates is called the calcium carbonate compensation depth or calcite compensation depth, or simply the CCD. The lysocline represents the depths where the rate of calcium carbonate dissolution increases dramatically (similar to the thermocline and halocline). At depths shallower than the CCD carbonate accumulation will exceed the rate of dissolution, and carbonate sediments will be deposited. In areas deeper than the CCD, the rate of dissolution will exceed production, and no carbonate sediments can accumulate (see diagram at right). The CCD is usually found at depths of 4 – 4.5 km, although it is much shallower at the poles where the surface water is cold. Thus calcareous oozes will mostly be found in tropical or temperate waters less than about 4 km deep, such as along the mid-ocean ridge systems and atop seamounts and plateaus. | Marine sediment | Wikipedia | 509 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
The CCD is deeper in the Atlantic than in the Pacific since the Pacific contains more CO2, making the water more acidic and calcium carbonate more soluble. This, along with the fact that the Pacific is deeper, means that the Atlantic contains more calcareous sediment than the Pacific. All told, about 48% of the seafloor is dominated by calcareous oozes.
Much of the rest of the deep ocean floor (about 38%) is dominated by abyssal clays. This is not so much a result of an abundance of clay formation, but rather the lack of any other types of sediment input. The clay particles are mostly of terrestrial origin, but because they are so small they are easily dispersed by wind and currents, and can reach areas inaccessible to other sediment types. Clays dominate in the central North Pacific, for example. This area is too far from land for coarse lithogenous sediment to reach, it is not productive enough for biogenous tests to accumulate, and it is too deep for calcareous materials to reach the bottom before dissolving.
Because clay particles accumulate so slowly, the clay-dominated deep ocean floor is often home to hydrogenous sediments like manganese nodules. If any other type of sediment was produced here it would accumulate much more quickly and would bury the nodules before they had a chance to grow.
Coastal sediments
Shallow water marine environments are found in areas between the shore and deeper water, such as a reef wall or a shelf break. The water in this environment is shallow and clear, allowing the formation of different sedimentary structures, carbonate rocks, coral reefs, and allowing certain organisms to survive and become fossils.
The sediment itself is often composed of limestone, which forms readily in shallow, warm calm waters. The shallow marine environments are not exclusively composed of siliciclastic or carbonaceous sediments. While they cannot always coexist, it is possible to have a shallow marine environment composed solely of carbonaceous sediment or one that is composed completely of siliciclastic sediment. Shallow water marine sediment is made up of larger grain sizes because smaller grains have been washed out to deeper water. Within sedimentary rocks composed of carbonaceous sediment, there may also be evaporite minerals. The most common evaporite minerals found within modern and ancient deposits are gypsum, anhydrite, and halite; they can occur as crystalline layers, isolated crystals or clusters of crystals. | Marine sediment | Wikipedia | 492 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
In terms of geologic time, it is said that most Phanerozoic sedimentary rock was deposited in shallow marine environments as about 75% of the sedimentary carapace is made up of shallow marine sediments; it is then assumed that Precambrian sedimentary rocks were too, deposited in shallow marine waters, unless it is specifically identified otherwise. This trend is seen in the North American and Caribbean region. Also, as a result of supercontinent breakup and other shifting tectonic plate processes, shallow marine sediment displays large variations in terms of quantity in the geologic time.
Bioturbation
Bioturbation is the reworking of sediment by animals or plants. These include burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a primary driver of biodiversity. The formal study of bioturbation began in the 1800s by Charles Darwin experimenting in his garden. The disruption of aquatic sediments and terrestrial soils through bioturbating activities provides significant ecosystem services. These include the alteration of nutrients in aquatic sediment and overlying water, shelter to other species in the form of burrows in terrestrial and water ecosystems, and soil production on land.
Bioturbators are ecosystem engineers because they alter resource availability to other species through the physical changes they make to their environments. This type of ecosystem change affects the evolution of cohabitating species and the environment, which is evident in trace fossils left in marine and terrestrial sediments. Other bioturbation effects include altering the texture of sediments (diagenesis), bioirrigation, and displacement of microorganisms and non-living particles. Bioturbation is sometimes confused with the process of bioirrigation, however these processes differ in what they are mixing; bioirrigation refers to the mixing of water and solutes in sediments and is an effect of bioturbation
Walruses and salmon are examples of large bioturbators. Although the activities of these large macrofaunal bioturbators are more conspicuous, the dominant bioturbators are small invertebrates, such as polychaetes, ghost shrimp and mud shrimp. The activities of these small invertebrates, which include burrowing and ingestion and defecation of sediment grains, contribute to mixing and the alteration of sediment structure. | Marine sediment | Wikipedia | 471 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Bioirrigation
Bioirrigation is the process of benthic organisms flushing their burrows with overlying water. The exchange of dissolved substances between the porewater and overlying seawater that results is an important process in the context of the biogeochemistry of the oceans. Coastal aquatic environments often have organisms that destabilize sediment. They change the physical state of the sediment. Thus improving the conditions for other organisms and themselves. These organisms often also cause Bioturbation, which is commonly used interchangeably or in reference with bioirrigation.
Bioirrigation works as two different processes. These processes are known as particle reworking and ventilation, which is the work of benthic macro-invertebrates (usually ones that burrow). This particle reworking and ventilation is caused by the organisms when they feed (faunal feeding), defecate, burrow, and respire. Bioirrigation is responsible for a large amount of oxidative transport and has a large impact on biogeochemical cycles.
Pelagic sediments
Pelagic sediments, or pelagite, are fine-grained sediments that accumulate as the result of the settling of particles to the floor of the open ocean, far from land. These particles consist primarily of either the microscopic, calcareous or siliceous shells of phytoplankton or zooplankton; clay-size siliciclastic sediment; or some mixture of these. Trace amounts of meteoric dust and variable amounts of volcanic ash also occur within pelagic sediments.
Based upon the composition of the ooze, there are three main types of pelagic sediments: siliceous oozes, calcareous oozes, and red clays.
An extensive body of work on deep-water processes and sediments has been built over the past 150 years since the voyage of HMS Challenger (1872–1876), during which the first systematic study of seafloor sediments was made. For many decades since that pioneering expedition, and through the first half of the twentieth century, the deep sea was considered entirely pelagic in nature. | Marine sediment | Wikipedia | 436 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
The composition of pelagic sediments is controlled by three main factors. The first factor is the distance from major landmasses, which affects their dilution by terrigenous, or land-derived, sediment. The second factor is water depth, which affects the preservation of both siliceous and calcareous biogenic particles as they settle to the ocean bottom. The final factor is ocean fertility, which controls the amount of biogenic particles produced in surface waters.
Turbidites
Turbidites are the geologic deposits of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Turbidites are deposited in the deep ocean troughs below the continental shelf, or similar structures in deep lakes, by underwater avalanches which slide down the steep slopes of the continental shelf edge. When the material comes to rest in the ocean trough, it is the sand and other coarse material which settles first followed by mud and eventually the very fine particulate matter. This sequence of deposition creates the Bouma sequences that characterize these rocks.
Turbidites were first recognised in the 1950s and the first facies model was developed by Bouma in 1962. Since that time, turbidites have been one of the better known and most intensively studied deep-water sediment facies. They are now very well known from sediment cores recovered from modern deep-water systems, subsurface (hydrocarbon) boreholes and ancient outcrops now exposed on land. Each new study of a particular turbidite system reveals specific deposit characteristics and facies for that system. The most commonly observed facies have been variously synthesised into a range of facies schemes.
Contourites
A contourite is a sedimentary deposit commonly formed on continental rise to lower slope settings, although they may occur anywhere that is below storm wave base. Countourites are produced by thermohaline-induced deepwater bottom currents and may be influenced by wind or tidal forces. The geomorphology of contourite deposits is mainly influenced by the deepwater bottom-current velocity, sediment supply, and seafloor topography. | Marine sediment | Wikipedia | 450 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Contourites were first identified in the early 1960s by Bruce Heezen and co-workers at Woods Hole Oceanographic Institute. Their now seminal paper demonstrated the very significant effects of contour-following bottom currents in shaping sedimentation on the deep continental rise off eastern North America. The deposits of these semi-permanent alongslope currents soon became known as contourites, and the demarcation of slope-parallel, elongate and mounded sediment bodies made up largely of contourites became known as contourite drifts.
Hemipelagic
Hemipelagic sediments, or hemipelagite, are a type of marine sediments that consists of clay and silt-sized grains that are terrigenous and some biogenic material derived from the landmass nearest the deposits or from organisms living in the water. Hemipelagic sediments are deposited on continental shelves and continental rises, and differ from pelagic sediment compositionally. Pelagic sediment is composed of primarily biogenic material from organisms living in the water column or on the seafloor and contains little to no terrigenous material. Terrigenous material includes minerals from the lithosphere like feldspar or quartz. Volcanism on land, wind blown sediments as well as particulates discharged from rivers can contribute to Hemipelagic deposits. These deposits can be used to qualify climatic changes and identify changes in sediment provenances.
Ecology
Benthos () is the community of organisms that live on, in, or near the seafloor, also known as the benthic zone.
Hyperbenthos (or hyperbenthic organisms), prefix , live just above the sediment.
Epibenthos (or epibenthic organisms), prefix , live on top of the sediments.
Endobenthos (or endobenthic organisms), prefix , live buried, or burrowing in the sediment, often in the oxygenated top layer.
Microbenthos | Marine sediment | Wikipedia | 398 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Marine microbenthos are microorganisms that live in the benthic zone of the ocean – that live near or on the seafloor, or within or on surface seafloor sediments. The word benthos comes from Greek, meaning "depth of the sea". Microbenthos are found everywhere on or about the seafloor of continental shelves, as well as in deeper waters, with greater diversity in or on seafloor sediments. In shallow waters, seagrass meadows, coral reefs and kelp forests provide particularly rich habitats. In photic zones benthic diatoms dominate as photosynthetic organisms. In intertidal zones changing tides strongly control opportunities for microbenthos.
Diatoms form a (disputed) phylum containing about 100,000 recognised species of mainly unicellular algae. Diatoms generate about 20 per cent of the oxygen produced on the planet each year, take in over 6.7 billion metric tons of silicon each year from the waters in which they live, and contribute nearly half of the organic material found in the oceans.
Coccolithophores are minute unicellular photosynthetic protists with two flagella for locomotion. Most of them are protected by a shell covered with ornate circular plates or scales called coccoliths. The coccoliths are made from calcium carbonate. The term coccolithophore derives from the Greek for a seed carrying stone, referring to their small size and the coccolith stones they carry. Under the right conditions they bloom, like other phytoplankton, and can turn the ocean milky white.
Radiolarians are unicellular predatory protists encased in elaborate globular shells usually made of silica and pierced with holes. Their name comes from the Latin for "radius". They catch prey by extending parts of their body through the holes. As with the silica frustules of diatoms, radiolarian shells can sink to the ocean floor when radiolarians die and become preserved as part of the ocean sediment. These remains, as microfossils, provide valuable information about past oceanic conditions. | Marine sediment | Wikipedia | 448 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Like radiolarians, foraminiferans (forams for short) are single-celled predatory protists, also protected with shells that have holes in them. Their name comes from the Latin for "hole bearers". Their shells, often called tests, are chambered (forams add more chambers as they grow). The shells are usually made of calcite, but are sometimes made of agglutinated sediment particles or chiton, and (rarely) of silica. Most forams are benthic, but about 40 species are planktic. They are widely researched with well established fossil records which allow scientists to infer a lot about past environments and climates.
Both foraminifera and diatoms have planktonic and benthic forms, that is, they can drift in the water column or live on sediment at the bottom of the ocean. Either way, their shells end up on the seafloor after they die. These shells are widely used as climate proxies. The chemical composition of the shells are a consequence of the chemical composition of the ocean at the time the shells were formed. Past water temperatures can be also be inferred from the ratios of stable oxygen isotopes in the shells, since lighter isotopes evaporate more readily in warmer water leaving the heavier isotopes in the shells. Information about past climates can be inferred further from the abundance of forams and diatoms, since they tend to be more abundant in warm water.
The sudden extinction event which killed the dinosaurs 66 million years ago also rendered extinct three-quarters of all other animal and plant species. However, deep-sea benthic forams flourished in the aftermath. In 2020 it was reported that researchers have examined the chemical composition of thousands of samples of these benthic forams and used their findings to build the most detailed climate record of Earth ever.
Some endoliths have extremely long lives. In 2013 researchers reported evidence of endoliths in the ocean floor, perhaps millions of years old, with a generation time of 10,000 years. These are slowly metabolizing and not in a dormant state. Some Actinomycetota found in Siberia are estimated to be half a million years old.
Sediment cores
The diagram on the right shows an example of a sediment core. The sample was retrieved from the Upernavik Fjord circa 2018. Grain-size measurements were made, and the top 50 cm was dated with the 210Pb method.
Carbon processing | Marine sediment | Wikipedia | 505 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Thinking about ocean carbon and carbon sequestration has shifted in recent years from a structurally-based chemical reactivity viewpoint toward a view that includes the role of the ecosystem in organic carbon degradation rates. This shift in view towards organic carbon and ecosystem involvement includes aspects of the "molecular revolution" in biology, discoveries on the limits of life, advances in quantitative modelling, paleo studies of ocean carbon cycling, novel analytical techniques, and interdisciplinary efforts. In 2020, LaRowe et al. outlined a broad view of this issue that is spread across multiple scientific disciplines related to marine sediments and global carbon cycling.
Evolutionary history
To begin with, the Earth was molten due to extreme volcanism and frequent collisions with other bodies. Eventually, the outer layer of the planet cooled to form a solid crust and water began accumulating in the atmosphere. The Moon formed soon afterwards, possibly as a result of the impact of a planetoid with the Earth. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, augmented by ice delivered from comets, produced the oceans.
By the start of the Archean, about four billion years ago, rocks were often heavily metamorphized deep-water sediments, such as graywackes, mudstones, volcanic sediments and banded iron formations. Greenstone belts are typical Archean formations, consisting of alternating high- and low-grade metamorphic rocks. High-grade rocks were derived from volcanic island arcs, while low-grade metamorphic rocks represented deep-sea sediments eroded from the neighboring island rocks and deposited in a forearc basin. The earliest-known supercontinent Rodinia assembled about one billion years ago, and began to break apart after about 250 million years during the latter part of the Proterozoic. | Marine sediment | Wikipedia | 361 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
The Paleozoic, (Ma), started shortly after the breakup of Pannotia and at the end of a global ice age. Throughout the early Paleozoic, the Earth's landmass was broken up into a substantial number of relatively small continents. Toward the end of the era the continents gathered together into a supercontinent called Pangaea, which included most of the Earth's land area. During the Silurian, which started 444 Ma, Gondwana continued a slow southward drift to high southern latitudes. The melting of ice caps and glaciers contributed to a rise in sea levels, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. Other cratons and continent fragments drifted together near the equator, starting the formation of a second supercontinent known as Euramerica.
During the Triassic deep-ocean sediments were laid down and subsequently disappeared through the subduction of oceanic plates, so very little is known of the Triassic open ocean. The supercontinent Pangaea rifted during the Triassic – especially late in the period – but had not yet separated. The first non-marine sediments in the rift that marks the initial break-up of Pangea are of Late Triassic age. Because of the limited shoreline of one super-continental mass, Triassic marine deposits are globally relatively rare; despite their prominence in Western Europe where the Triassic was first studied. In North America, for example, marine deposits are limited to a few exposures in the west. Thus Triassic stratigraphy is mostly based on organisms living in lagoons and hypersaline environments, such as Estheria crustaceans and terrestrial vertebrates. | Marine sediment | Wikipedia | 349 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Patterns or traces of bioturbation are preserved in lithified rock. The study of such patterns is called ichnology, or the study of "trace fossils", which, in the case of bioturbators, are fossils left behind by digging or burrowing animals. This can be compared to the footprint left behind by these animals. In some cases bioturbation is so pervasive that it completely obliterates sedimentary structures, such as laminated layers or cross-bedding. Thus, it affects the disciplines of sedimentology and stratigraphy within geology. The study of bioturbator ichnofabrics uses the depth of the fossils, the cross-cutting of fossils, and the sharpness (or how well defined) of the fossil to assess the activity that occurred in old sediments. Typically the deeper the fossil, the better preserved and well defined the specimen.
Important trace fossils from bioturbation have been found in marine sediments from tidal, coastal and deep sea sediments. In addition sand dune, or Eolian, sediments are important for preserving a wide variety of fossils. Evidence of bioturbation has been found in deep-sea sediment cores including into long records, although the act extracting the core can disturb the signs of bioturbation, especially at shallower depths. Arthropods, in particular are important to the geologic record of bioturbation of Eolian sediments. Dune records show traces of burrowing animals as far back as the lower Mesozoic, 250 Ma, although bioturbation in other sediments has been seen as far back as 550 Ma.
Research history
The first major study of deep-ocean sediments occurred between 1872 and 1876 with the HMS Challenger expedition, which travelled nearly 70,000 nautical miles sampling seawater and marine sediments. The scientific goals of the expedition were to take physical measurements of the seawater at various depths, as well as taking samples so the chemical composition could be determined, along with any particulate matter or marine organisms that were present. This included taking samples and analysing sediments from the deep ocean floor. Before the Challenger voyage, oceanography had been mainly speculative. As the first true oceanographic cruise, the Challenger expedition laid the groundwork for an entire academic and research discipline. | Marine sediment | Wikipedia | 458 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
Earlier theories of continental drift proposed that continents in motion "plowed" through the fixed and immovable seafloor. Later in the 1960s the idea that the seafloor itself moves and also carries the continents with it as it spreads from a central rift axis was proposed by Harold Hess and Robert Dietz. The phenomenon is known today as plate tectonics. In locations where two plates move apart, at mid-ocean ridges, new seafloor is continually formed during seafloor spreading. In 1968, the oceanographic research vessel Glomar Challenger was launched and embarked on a 15-year-long program, the Deep Sea Drilling Program. This program provided crucial data that supported the seafloor spreading hypothesis by collecting rock samples that confirmed that the farther from the mid-ocean ridge, the older the rock was. | Marine sediment | Wikipedia | 166 | 11779912 | https://en.wikipedia.org/wiki/Marine%20sediment | Physical sciences | Oceanography | Earth science |
A speculum (Latin for 'mirror'; : specula or speculums) is a medical tool for investigating body orifices, with a form dependent on the orifice for which it is designed. In old texts, the speculum may also be referred to as a diopter or dioptra. Like an endoscope, a speculum allows a view inside the body; endoscopes, however, tend to have optics while a speculum is intended for direct vision.
History
Vaginal and anal specula were used by the ancient Greeks and Romans, and speculum artifacts have been found in Pompeii. The modern vaginal speculum, developed by J. Marion Sims, consists of a hollow cylinder with a rounded end that is divided into two hinged parts, somewhat like the beak of a duck. This speculum is inserted into the vagina to dilate it for examination of the vagina and cervix.
The modern vaginal speculum was developed by J. Marion Sims, a plantation doctor in Lancaster County, United States. Between 1845 and 1849, Sims performed dozens of surgeries, without anesthesia, on at least 12 enslaved women. In these experiments, Sims developed a technique to repair fistula and in the process invented the duckbill speculum. These experiments, and the development of the modern specula, led some to regard Sims as the "father of modern gynaecology."
By the 1860s, specula were integrated into criminal justice practices in the UK. In Great Britain, examinations of the cervix were made mandatory for all women convicted of prostitution by the country's Contagious Disease Act.
In the 19th century, the vaginal speculum became a cultural symbol of the tenuous relationship between women and their physicians. Use of the speculum was generally avoided in medical practices, and most vaginal conditions were diagnosed through symptoms or palpating the abdomen. Many practitioners had moral concerns about the use of the speculum, and preferred to diagnose through palpating the abdomen. As late as 1910, physicians believed the vaginal speculum to be inferior to the "educated touch." | Speculum (medicine) | Wikipedia | 443 | 320320 | https://en.wikipedia.org/wiki/Speculum%20%28medicine%29 | Biology and health sciences | Diagnostics | Health |
These concerns continued into the early 20th century as the speculum became commonplace in gynecology practices. Often, nurses played a major role in ensuring the proper use of the speculum during medical exams. The 1946 and 1956 editions of a multi-volume gynecology text for nurses required that nurses remain present during examination to protect both the patient and physician from "blackmail by designing persons."
, 85% of gynecologists are women. As a result of this demographic shift, the procedures around speculum use have also changed.
Construction
Specula have been made of glass or metal. They were generally made of stainless steel and sterilized between uses, but particularly in the 21st century, many — especially those used in emergency departments and doctor's offices — are made of plastic, and are disposable, single-use items. Those used in surgical suites are still commonly made of stainless steel.
Types
Specula come in a variety of shapes based on their purpose, and a variety of sizes; in any case the cylinder or bill(s) of the instrument allow the operator a direct vision of the area of interest and the possibility to introduce instruments for further interventions such as a biopsy.
Vaginal
The most common specula used in gynecologic practice are varying sizes of bivalved vaginal speculum; the two bills are hinged and are "closed" when the speculum is inserted to facilitate its entry and "opened" in its final position where they can be arrested by a screw mechanism, so that the operator is freed from keeping the bills apart.
A cylindrical-shaped speculum, introduced in 2001, the dilating vaginal speculum (also known as the Veda-scope) invented by Clemens van der Weegen, inflates the vagina with filtered air. (see diagram) The device has two main functions: a) to take a normal Pap smear with a cervical brush or a cytology brush; and b) as an internal colposcope so that the operator can pivot the Veda-scope to view any part of the vagina barrel and cervix facilitated by an internal light source that can illuminate the vaginal wall and cervix with multi-coloured light filters, which can detect pre-cancerous cells with the aid of acetic acid solution and iodine solution. It also has a facility to attach a digital camera for viewing and recording. | Speculum (medicine) | Wikipedia | 496 | 320320 | https://en.wikipedia.org/wiki/Speculum%20%28medicine%29 | Biology and health sciences | Diagnostics | Health |
A specialized form of vaginal speculum is the weighted speculum, which consists of a broad half tube which is bent at about a 90-degree angle, with the channel of the tube on the exterior side of the angle. One end of the tube has a roughly spherical metal weight surrounding the channel of the speculum. A weighted speculum is placed in the vagina during vaginal surgery with the patient in the lithotomy position. The weight holds the speculum in place and frees the surgeon's hands for other tasks.
A vaginal speculum is also used in fertility treatments, particularly artificial insemination, and allows the vaginal cavity to be opened and observed thereby facilitating the deposit of semen into the vagina.
Cylindrical shape
One bill
Two bills (bivalved)
Three bills
Rectal
Vaginal specula are also used for anal surgery, although several other forms of anal specula exist. One form, the anoscope, resembles a tube that has a removable bullet-shaped insert. When the anoscope is inserted into the anus, the insert dilates the anus to the diameter of the tube. The insert is then removed, leaving the tube to allow examination of the lower rectum and anus.
This style of anal speculum is one of the oldest designs for surgical instruments still in use, with examples dating back many centuries. The sigmoidoscope can be further advanced into the lower intestinal tract and requires an endoscopic set-up.
Tubal shape
One bill
Two bills
Three bills
Nasal
Nasal specula have two relatively flat bills with handle. The instrument is hinged so that when the handles are squeezed together the bills spread laterally, allowing examination.
Additionally, the Thudichum nasal speculum is commonly used in the outpatient examination of the nose.
Aural
Ear or aural specula resemble a funnel, and come in a variety of sizes.
Eyelid
For ophthalmic surgery such as cataract surgery, a speculum designed to retract the eyelids is used.
Oral
In veterinary medicine, a McPherson Speculum can be used for oral examination. The speculum helps keep the mouth open during the exam and helps avoid biting injuries.
Non-medical use
Specula are used for sexual pleasure, both vaginally and anally. | Speculum (medicine) | Wikipedia | 471 | 320320 | https://en.wikipedia.org/wiki/Speculum%20%28medicine%29 | Biology and health sciences | Diagnostics | Health |
A hand axe (or handaxe or Acheulean hand axe) is a prehistoric stone tool with two faces that is the longest-used tool in human history. It is made from stone, usually flint or chert that has been "reduced" and shaped from a larger piece by knapping, or hitting against another stone. They are characteristic of the lower Acheulean and middle Palaeolithic (Mousterian) periods, roughly 1.6 million years ago to about 100,000 years ago, and used by Homo erectus and other early humans, but rarely by Homo sapiens.
Their technical name (biface) comes from the fact that the archetypical model is a generally bifacial (with two wide sides or faces) and almond-shaped (amygdaloidal) lithic flake. Hand axes tend to be symmetrical along their longitudinal axis and formed by pressure or percussion. The most common hand axes have a pointed end and rounded base, which gives them their characteristic almond shape, and both faces have been knapped to remove the natural cortex, at least partially. Hand axes are a type of the somewhat wider biface group of two-faced tools or weapons.
Hand axes were the first prehistoric tools to be recognized as such: the first published representation of a hand axe was drawn by John Frere and appeared in a British publication in 1800. Until that time, their origins were thought to be natural or supernatural. They were called thunderstones, because popular tradition held that they had fallen from the sky during storms or were formed inside the earth by a lightning strike and then appeared at the surface. They are used in some rural areas as an amulet to protect against storms.
Handaxes are generally thought to have been primarily used as cutting tools, with the wide base serving as an ergonomic area for the hand to grip the tool, though other uses, such as throwing weapons and use as social and sexual signaling have been proposed.
Terminology
The four classes of hand axe are:
Large, thick hand axes reduced from cores or thick flakes, referred to as blanks
Thinned blanks. While form remains rough and uncertain, an effort has been made to reduce the thickness of the flake or core
Either a preform or crude formalized tool, such as an adze
Finer formalized tool types such as projectile points and fine bifaces | Hand axe | Wikipedia | 484 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
While Class 4 hand axes are referred to as "formalized tools", bifaces from any stage of a lithic reduction sequence may be used as tools. (Other biface typologies make five divisions rather than four.)
French antiquarian André Vayson de Pradenne introduced the word in 1920. This term co-exists with the more popular hand axe (), that was coined by Gabriel de Mortillet much earlier. The continued use of the word biface by François Bordes and Lionel Balout supported its use in France and Spain, where it replaced the term hand axe. Use of the expression hand axe has continued in English as the equivalent of the French ( in Spanish), while biface applies more generally for any piece that has been carved on both sides by the removal of shallow or deep flakes. The expression is used in German; it can be literally translated as hand axe, although in a stricter sense it means "fist wedge". It is the same in Dutch where the expression used is which literally means "fist axe". The same locution occurs in other languages. | Hand axe | Wikipedia | 229 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
However, the general impression of these tools was based on ideal (or classic) pieces that were of such perfect shape that they caught the attention of non-experts. Their typology broadened the term's meaning. Biface hand axes and bifacial lithic items are distinguished. A hand axe need not be a bifacial item and many bifacial items are not hand axes. Nor were hand axes and bifacial items exclusive to the Lower Palaeolithic period in the Old World. They appear throughout the world and in many different pre-historical epochs, without necessarily implying an ancient origin. Lithic typology is not a reliable chronological reference and was abandoned as a dating system. Examples of this include the "quasi-bifaces" that sometimes appear in strata from the Gravettian, Solutrean and Magdalenian periods in France and Spain, the crude bifacial pieces of the Lupemban culture (9000 B.C.) or the pyriform tools found near Sagua La Grande in Cuba. The word biface refers to something different in English than in French or in Spanish, which could lead to many misunderstandings. Bifacially carved cutting tools, similar to hand axes, were used to clear scrub vegetation throughout the Neolithic and Chalcolithic periods. These tools are similar to more modern adzes and were a cheaper alternative to polished axes. The modern day villages along the Sepik river in New Guinea continue to use tools that are virtually identical to hand axes to clear forest. "The term biface should be reserved for items from before the Würm II-III interstadial", although certain later objects could exceptionally be called bifaces.
Hand axe does not relate to axe, which was overused in lithic typology to describe a wide variety of stone tools. At the time the use of such items was not understood. In the particular case of Palaeolithic hand axes the term axe is an inadequate description. Lionel Balout stated, "the term should be rejected as an erroneous interpretation of these objects that are not 'axes. Subsequent studies supported this idea, particularly those examining the signs of use.
Materials
Hand axes are mainly made of flint, but rhyolites, phonolites, quartzites and other coarse rocks were used as well. Obsidian, natural volcanic glass, shatters easily and was rarely used. | Hand axe | Wikipedia | 494 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Uses
Most researchers think that handaxes were primarily used as cutting tools. The pioneers of Palaeolithic tool studies first suggested that bifaces were used as axes despite the fact that they have a sharp border all around. Other uses seem to show that hand axes were a multi-functional tool, leading some to describe them as the "Acheulean Swiss Army knife". Other academics have suggested that the hand axe was simply a byproduct of being used as a core to make other tools, a weapon, or was perhaps used ritually.
Wells proposed in 1899 that hand axes were used as missile weapons to hunt prey – an interpretation supported by Calvin, who suggested that some of the rounder specimens of Acheulean hand axes were used as hunting projectiles or as "killer frisbees" meant to be thrown at a herd of animals at a water hole so as to stun one of them. This assertion was inspired by findings from the Olorgesailie archaeological site in Kenya. Few specimens indicate hand axe hafting, and some are too large for that use. However, few hand axes show signs of heavy damage indicative of throwing, modern experiments have shown the technique to often result in flat-faced landings, and many modern scholars consider the "hurling" theory to be poorly conceived but so attractive that it has taken a life of its own.
As hand axes can be recycled, resharpened and remade, they could have been used for varied tasks. For this reason it may be misleading to think of them as axes, they could have been used for tasks such as digging, cutting, scraping, chopping, piercing and hammering. However, other tools, such as small knives, are better suited for some of these tasks, and many hand axes have been found with no traces of use.
Baker suggested that since so many hand axes have been found that have no retouching, perhaps the hand axe was not itself a tool, but a large lithic core from which flakes had been removed and used as tools (flake core theory). On the other hand, there are many hand axes found with retouching such as sharpening or shaping, which casts doubt on this idea. | Hand axe | Wikipedia | 450 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Other theories suggest the shape is part tradition and part by-product of its manufacture. Many early hand axes appear to be made from simple rounded pebbles (from river or beach deposits). It is necessary to detach a 'starting flake', often much larger than the rest of the flakes (due to the oblique angle of a rounded pebble requiring greater force to detach it), thus creating an asymmetry. Correcting the asymmetry by removing material from the other faces, encouraged a more pointed (oval) form factor. (Knapping a completely circular hand axe requires considerable correction of the shape.) Studies in the 1990s at Boxgrove, in which a butcher attempted to cut up a carcass with a hand axe, revealed that the hand axe was able to expose bone marrow. | Hand axe | Wikipedia | 165 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Kohn and Mithen independently arrived at the explanation that symmetric hand axes were favoured by sexual selection as fitness indicators. Kohn in his book As We Know It wrote that the hand axe is "a highly visible indicator of fitness, and so becomes a criterion of mate choice." Miller followed their example and said that hand axes have characteristics that make them subject to sexual selection, such as that they were made for over a million years throughout Africa, Europe and Asia, they were made in large numbers, and most were impractical for utilitarian use. He claimed that a single design persisting across time and space cannot be explained by cultural imitation and draws a parallel between bowerbirds' bowers (built to attract potential mates and used only during courtship) and Pleistocene hominids' hand axes. He called hand axe building a "genetically inherited propensity to construct a certain type of object." He discards the idea that they were used as missile weapons because more efficient weapons were available, such as javelins. Although he accepted that some hand axes may have been used for practical purposes, he agreed with Kohn and Mithen who showed that many hand axes show considerable skill, design and symmetry beyond that needed for utility. Some were too big, such as the Maritime Academy handaxe or the "Great Hand Axe" found in Furze Platt, England that is 30.6 cm long (other scholars measure it as 39.5 cm long). Some were too small - less than two inches. Some were "overdetermined", featuring symmetry beyond practical requirements and showing evidence of unnecessary attention to form and finish. Some were actually made out bone instead of stone and thus were not very practical, suggesting a cultural or ritual use. Miller thinks that the most important clue is that under electron microscopy hand axes show no signs of use or evidence of edge wear. Others argue that little evidence for use-wear simply relates to the particular sedimentological conditions, rather than being evidence of discarding without use. It has been noted that hand axes can be good handicaps in Zahavi's handicap principle theory: learning costs are high, risks of injury, they require physical strength, hand-eye coordination, planning, patience, pain tolerance and resistance to infection from cuts and bruises when making or using such a hand axe. | Hand axe | Wikipedia | 471 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Evidence from wear analysis
The use-wear analysis of Palaeolithic hand axes is carried out on findings from emblematic sites across nearly all of Western Europe. Keeley and Semenov were the pioneers of this specialized investigation. Keeley stated, "The morphology of typical hand axes suggests a greater range of potential activities than those of flakes".
Many problems need to be overcome in carrying out this type of analysis. One is the difficulty in observing larger pieces with a microscope. Of the millions of known pieces and despite their long role in human history, few have been thoroughly studied. Another arises from the clear evidence that the same tasks were performed more effectively using utensils made from flakes:
Keeley based his observations on archaeological sites in England. He proposed that in base settlements where it was possible to predict future actions and where greater control on routine activities was common, the preferred tools were made from specialized flakes, such as racloirs, backed knives, scrapers and punches. However, hand axes were more suitable on expeditions and in seasonal camps, where unforeseen tasks were more common. Their main advantage in these situations was the lack of specialization and adaptability to multiple eventualities. A hand axe has a long blade with different curves and angles, some sharper and others more resistant, including points and notches. All of this is combined in one tool. Given the right circumstances, it is possible to make use of loose flakes. In the same book, Keeley states that a number of the hand axes studied were used as knives to cut meat (such as hand axes from Hoxne and Caddington). He identified that the point of another hand axe had been used as a clockwise drill. This hand axe came from Clacton-on-Sea (all of these sites are located in the east of England). Toth reached similar conclusions for pieces from the Spanish site in Ambrona (Soria). Analysis carried out by Domínguez-Rodrigo and co-workers on the primitive Acheulean site in Peninj (Tanzania) on a series of tools dated 1.5 mya shows clear microwear produced by plant phytoliths, suggesting that the hand axes were used to work wood. Among other uses, use-wear evidence for fire making has been identified on dozens of later Middle Palaeolithic hand axes from France, suggesting Neanderthals struck these tools with the mineral pyrite to produce sparks at least 50,000 years ago. | Hand axe | Wikipedia | 510 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Macroscopic traces
Some hand axes were used with force that left clearly visible marks. Other visible marks can be left as the scars from retouching, on occasion it is possible to distinguish them from marks left by the initial manufacture. One of the most common cases is when a point breaks. This was seen at sites in Europe, Africa and Asia. One example comes from the El Basalito site in Salamanca, where excavation uncovered fragments of a hand axe with marks at the tip that appeared to be the result of the action of a wedge, which would have subjected the object to high levels of torsion that broke the tip. A break or extreme wear can affect a tool's point or any other part. Such wear was reworked by means of a secondary working as discussed above. In some cases this reconstruction is easily identifiable and was carried out using techniques such as the (French, meaning "tranchet blow"), or simply with scale or scalariform retouches that alter an edge's symmetry and line.
Forms
The most characteristic and common shape is a pointed area at one end, cutting edges along its side and a rounded base (this includes hand axes with a lanceolate and amygdaloidal shape as well as others from the family). The axes are almost always symmetrical despite studies showing that hand axe symmetry does not help in tasks such as skinning animals. While there is a "typical" shape to most hand axes, there are some displaying a variety of shapes, including circular, triangular and elliptical—calling in to question the contention that they had a constant and only symbolic significance. They are typically between long, although they can be bigger or smaller.
They were typically made from a rounded stone, a block or lithic flake, using a hammer to remove flakes from both sides of the item. This hammer can be made of hard stone, or of wood or antler. The latter two, softer hammers can produce more delicate results. However, a hand axe's technological aspect can reflect more differences. For example, uniface tools have only been worked on one side and partial bifaces retain a high proportion of the natural cortex of the tool stone, often making them easy to confuse with chopping tools. Further, simple bifaces may have been created from a suitable tool stone, but they rarely show evidence of retouching. Later hand axes were improved by the use of the Levallois technique to make the more sophisticated and lighter Levallois core. | Hand axe | Wikipedia | 505 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
In summary, hand axes are recognized by many typological schools under different archaeological paradigms and are quite recognisable (at least the most typical examples). However, they have not been definitively categorized. Stated more formally, the idealised model combines a series of well-defined properties, but no set of these properties are necessary or sufficient to identify a hand axe.
History and distribution
In 1969 in the 2nd edition of World Prehistory, Grahame Clark proposed an evolutionary progression of flint-knapping industries (also known as complexes or technocomplexes) in which the "dominant lithic technologies" occurred in a fixed sequence where simple Oldowan one-edged tools were replaced by these more complex Acheulean hand axes, which were then eventually replaced by the even more complex Mousterian tools made with the Levallois technique.
The oldest known Oldowan tools were found in Gona, Ethiopia. These are dated to about 2.6 mya.
Early examples of hand axes date back to 1.6 mya in the later Oldowan (Mode I), called the "developed Oldowan" by Mary Leakey. These hand axes became more abundant in mode II Acheulean industries that appeared in Southern Ethiopia around 1.4 mya. Some of the best specimens come from 1.2 mya deposits in Olduvai Gorge.
By 1.8 mya early man was present in Europe. Remains of their activities were excavated in Spain at sites in the Guadix-Baza basin and near Atapuerca. Most early European sites yield "mode 1" or Oldowan assemblages. The earliest Acheulean sites in Europe appear around 0.5 mya. In addition, the Acheulean tradition did not spread to Eastern Asia. In Europe and particularly in France and England, the oldest hand axes appear after the Beestonian Glaciation–Mindel Glaciation, approximately 750,000 years ago, during the so-called Cromerian complex. They became more widely produced during the Abbevillian tradition. | Hand axe | Wikipedia | 429 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
The apogee of hand axe manufacture took place in a wide area of the Old World, especially during the Riss glaciation, in a cultural complex that can be described as cosmopolitan and which is known as the Acheulean. The use of hand axes survived the Middle Palaeolithic in a much smaller area and were especially important during the Mousterian, up to the middle of the Last glacial period.
Hand axes dating from the lower Palaeolithic were found on the Asian continent, on the Indian subcontinent and in the Middle East (to the south of parallel 40° N), but they were absent from the area to the east of the 90° E meridian. Movius designated a border (the so-called Movius Line) between the cultures that used hand axes to the west and those that made chopping tools and small retouched lithic flakes, such as were made by Peking Man and the Ordos culture in China, or their equivalents in Indochina such as the Hoabinhian. However, Movius' hypothesis was proved incorrect when many hand axes made in Palaeolithic era were found in 1978 at Hantan River, Jeongok, Yeoncheon County, South Korea for the first time in East Asia. Some of them are exhibited at the Jeongok Prehistory Museum, South Korea.
The Padjitanian culture from Java was traditionally thought to be the only oriental culture to manufacture hand axes. However, a site in Baise, Guangxi, China shows that hand axes were made in eastern Asia.
Hand axe technology is almost unknown in Australian prehistory, although a few have been found.
Construction
Experiments in knapping have demonstrated the relative ease with which a hand axe can be made, which could help explain their success. In addition, they demand relatively little maintenance and allow a choice of raw materials–any rock will suffice that supports a conchoidal fracture. With early hand axes, it is easy to improvise their manufacture, correct mistakes without requiring detailed planning, and no long or demanding apprenticeship is necessary to learn the necessary techniques. These factors combine to allow these objects to remain in use throughout pre-history. Their adaptability makes them effective in a variety of tasks, from heavy duty such as digging in soil, felling trees or breaking bones to delicate such as cutting ligaments, slicing meat or perforating a variety of materials. | Hand axe | Wikipedia | 493 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Later examples of hand axes are more sophisticated with their use of two layers of knapping (one made with stone knapping and one made with bone knapping).
Lastly, a hand axe represents a prototype that can be refined giving rise to more developed, specialised and sophisticated tools such as the tips of various projectiles, knives, adzes and hatchets.
Analysis
Given the typological difficulties in defining the essence of a hand axe, it is important when analysing them to take account of their archaeological context (geographical location, stratigraphy, the presence of other elements associated with the same level, chronology etc.). It is necessary to study their physical state to establish any natural alterations that may have occurred: patina, shine, wear and tear, mechanical, thermal and / or physical-chemical changes such as cracking, in order to distinguish these factors from the scars left during the tool's manufacture or use.
The raw material is an important factor, because of the result that can be obtained by working it and in order to reveal the economy and movement of prehistoric humans. In the Olduvai Gorge the raw materials were most readily available some ten kilometres from the nearest settlements. However, flint or silicate is readily available on the fluvial terraces of Western Europe. This means that different strategies were required for the procurement and use of available resources. The supply of materials was the most important factor in the manufacturing process as Palaeolithic artisans were able to adapt their methods to available materials, obtaining adequate results from even the most difficult raw materials. Despite this it is important to study the rock's grain, texture, the presence of joints, veins, impurities or shatter cones etc.
In order to study the use of individual items it is necessary to look for traces of wear such as pseudo-retouches, breakage or wear, including areas that are polished. If the item is in a good condition it is possible to submit it to use-wear analysis, which is discussed in more detail below. Apart from these generalities, which are common to all carved archaeological pieces, hand axes need a technical analysis of their manufacture and a morphological analysis. | Hand axe | Wikipedia | 442 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Technical analysis
The technical analysis of a hand axe tries to discover each of the phases in its chaîne opératoire (operational sequence). The chain is highly flexible, as a toolmaker may focus narrowly on just one of the sequence's links or equally on each link. The links examined in this type of study start with the extraction methods of the raw material, then include the actual manufacture of the item, its use, maintenance throughout its working life, and finally its disposal.
A toolmaker may put a lot of effort into finding the highest quality raw material or the most suitable tool stone. In this way more effort is invested in obtaining a good foundation, but time is saved on shaping the stone: that is, the effort is focused on the start of the operational chain. Equally the artisan may concentrate the most effort in the manufacture so that the quality or suitability of the raw material is less important. This will minimize the initial effort, but will result in a greater effort at the end of the operational chain.
Tool stone and cortex
Hand axes are most commonly made from rounded pebbles or nodules, but many are also made from a large flake. Hand axes made from flakes first appeared at the start of the Acheulean period and became more common with time. Manufacturing a hand axe from a flake is actually easier than from a pebble. It is also quicker, as flakes are more likely to be closer to the desired shape. This allows easier manipulation and fewer knaps are required to finish the tool; it is also easier to obtain straight edges. When analysing a hand axe made from a flake, it should be remembered that its shape was predetermined (by use of the Levallois technique or Kombewa technique or similar). Notwithstanding this, it is necessary to note a tool's characteristics: type of flake, heel, knap direction. | Hand axe | Wikipedia | 387 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
The natural external cortex or rind of the tool stone, which is due to erosion and the physical-chemical alterations of weathering, is different from the stone's interior. In the case of chert, quartz or quartzite, this alteration is basically mechanical, and apart from the colour and the wear it has the same characteristics as the interior in terms of hardness, toughness etc. However, flint is surrounded by a limestone cortex that is soft and unsuitable for stone tools. As hand axes are made from a tool stone's core, it is normal to indicate the thickness and position of the cortex in order to better understand the techniques that are required in their manufacture. The variation in cortex between utensils should not be taken as an indication of their age.
Many partially-worked hand axes do not require further work in order to be effective tools. They can be considered to be simple hand axes. Less suitable tool stone requires more thorough working. In some specimens the cortex is unrecognisable due to the complete working that it has undergone, which has eliminated any vestige of the original cortex.
Types
It is possible to distinguish multiple types of hand axe: | Hand axe | Wikipedia | 236 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Uniface—flaked on one face with cortex completely covering the other side. This characteristic does not disqualify such tools as hand axes and gives no indication of their age.
Partial biface—The cortex is present on the tool's base and central part. The overall area that is not knapped may extend to up to two thirds of its length.
Bifaces with basal cortex coverage—Only the artefact's base is covered with cortex, which does not cover more than a third of total length. In some cases the cortex is present on both the base and one side, thereby affecting one edge: such tools are called "natural backed". De Mortillet emphasised the importance of the presence or absence of the cortex around the edge in the 19th century: "Even on some of the best worked pieces it is common to see, sometimes on the base but more often on the side, a small area that has not been worked, that is uncut. It could be thought that this is a mistake or an error. But often the most probable reason for this is that it was intentional. There are a large number of hand axes with an uncut base, unworked or partially cleaned ... an area has intentionally been left on these pieces as a grip, it is called the heel. This heel acts as a handle as it is easy to grip". (This hypothesis remains unproven and is not commonly used.)
Hand axes with residual cortex on an edge—The whole of their edges are knapped except for a small area where the cortex remains (leaving a small area without a sharp edge). This area can be at the base, side or oblique. In all cases it is small, leaving cutting edges on both sides.
Hand axes with a cutting edge around the whole circumference—The circumference is knapped to a cutting edge, although some residual areas of cortex may persist on either face, without affecting the cutting edge's effectiveness.
Production
Older hand axes were produced by direct percussion with a stone hammer and can be distinguished by their thickness and a sinuous border. Mousterian hand axes were produced with a soft billet of antler or wood and are much thinner, more symmetrical and have a straight border. An experienced flintknapper needs less than 15 minutes to produce a good quality hand axe. A simple hand axe can be made from a beach pebble in less than 3 minutes. | Hand axe | Wikipedia | 505 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
The manufacturing process employs lithic reduction. This phase is commonly thought of as the most important in hand axe fabrication, although it is not always used, such as for hand axes made from flakes or a suitable tool stone. An important concern is the implement that has been used to form the biface. If multiple implements were used, it is essential to discover in what order they were used and the result obtained by each one. The most common implements are:
Hard hammer faces
Hand axes can be made without subsequent reworking of the edges. A hammerstone was the most common percussive tool used during the Acheulean. The resulting artefact is usually easily recognizable given its size and irregular edges, as the removed flakes leave pronounced percussion bulbs and compression rings. A hammerstone produces a small number of flakes that are wide and deep leaving long edges on the tool as their highly concave form yields curving edges. The cross-section is irregular, often sub-rhombic, while the intersection between the faces forms an acute angle of between 60° and 90° degrees. The shape is similar to that of the core as the irregularities formed during knapping are not removed. The notches obtained were exploited in the production sequence. It is common that this type of manufacture yields "partial bifaces" (an incomplete working that leaves many areas covered with cortex), "unifaces" (tools that have only been worked on one face), "bifaces in the Abbevillian style" and "nucleiform bifaces". This type of manufacturing style is generally an indication of the age when a tool was made and with other archaeological data can provide a context that allows its age to be estimated.
Hard hammer faces and edges | Hand axe | Wikipedia | 356 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
These hand axes have a more balanced appearance as the modification consists of a second (or third) series of blows to make the piece more uniform and provide a better finish. The modification is often called retouching and is sometimes carried out using invasive retouching or using softer, marginal, shallow blows that are only applied to the most marked irregularities leaving scale-like marks. The modification of edges with a hard hammer was carried out from the beginning of the Acheulean and persisted into the Mousterian. It is therefore not useful as an indicator of chronology (in order for it to be considered as a marker it has to be accompanied by other complementary and independent archaeological data). The hand axes arising from this methodology have a more classical profile with either a more symmetrical almond or oval shape and with a lower proportion of the cortex of the original core. It is not always the case that the retouching had the objective of reducing an edge's irregularities or deformities. In fact, it has been shown that in some cases the retouching was carried out to sharpen an edge that had been blunted by use or a point that had deteriorated.
Soft hammer finish
Some hand axes were formed with a hard hammer and finished with a soft hammer. Blows that result in deep conchoidal fractures (the first phase of manufacture) can be distinguished from features resulting from sharpening with a soft hammer. The latter leaves shallower, more distended, broader scars, sometimes with small, multiple shock waves. However, marks left by a small, hard hammer can leave similar marks to a soft hammer.
Soft hammer finished pieces are usually balanced and symmetrical, and can be relatively smooth. Soft hammer works first appeared in the Acheulean period, allowing tools with these markings to be used as a estimation, but with no greater precision. The main advantage of a soft hammer is that a flintknapper is able to remove broader, thinner flakes with barely developed heels, which allows a cutting edge to be maintained or even improved with minimal raw material wastage. However, a high-quality raw material is required to make their use effective. No studies compare the two methods in terms of yield per unit weight of raw material, or the difference in energy use. The use of a soft hammer requires greater use of force by the flintknapper and a steeper learning curve, although it offers more flakes for less raw material.
Soft hammer only | Hand axe | Wikipedia | 495 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
Hand axes made using only a soft hammer are much less common. In most cases at least initial work was done with a hard hammer, before subsequent flaking with a soft hammer erased all vestiges of that work. A soft hammer is not suitable for all types of percussion platform and it cannot be used on certain types of raw material. It is, therefore, necessary to start with a hard hammer or with a flake as a core as its edge will be fragile (flat, smooth pebbles are also useful). This means that although it was possible to manufacture a hand axe using a soft hammer, it is reasonable to suppose that a hard hammer was used to prepare a blank followed by one or more phases of retouching to finish the piece. However, the degree of separation between the phases is not certain, as the work could have been carried out in one operation.
Working with a soft hammer allows a knapper greater control of the knapping and reduces waste of the raw material, allowing the production of longer, sharper, more uniform edges that will increase the tool's working life. Hand axes made with a soft hammer are usually more symmetrical and smooth, with rectilinear edges and shallow indentations that are broad and smooth so that it is difficult to distinguish where one flake starts and another ends. They generally have a regular biconvex cross-section and the intersection of the two faces forms an edge with an acute angle, usually of around 30°. They were worked with great skill and therefore they are more aesthetically attractive. They are usually associated with periods of highly developed tool making such as the Micoquien or the Mousterian. Soft hammer manufacturing is not reliable as the sole dating method.
Hand axes were created to be tools and as such they wore out, deteriorated and/or broke during use. Relics have suffered dramatic changes throughout their useful lives. It is common to find edges that have been sharpened, points that have been reconstructed and profiles that have been deformed by reworking in order to extend the piece's useful lifetime. Some tools were recycled later, leading Bordes to note that hand axes "are sometimes found in the Upper Palaeolithic. Their presence, which is quite normal in the Perigordian I, is often due, in other levels, to the collection of Mousterian or Acheulean tools."
Morphology | Hand axe | Wikipedia | 487 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
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