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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. Thoma... | 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, Gloss... | 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... | 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 (Kun... | 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 foun... | 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 pr... | 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... | 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 ... | 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 mil... | 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... | 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 catchin... | 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 intro... | 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... | 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 ... | 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, t... | 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 ... | 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 speedom... | 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... | 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... | 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... | 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 err... | 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 faci... | 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 4... | 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 calcula... | 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 a... | 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 ... | 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... | 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. Th... | 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... | 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 w... | 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... | 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, Huaxia... | 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 su... | 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... | 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 int... | 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 ... | 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 ... | 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 ... | 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 Cart... | 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".... | 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 tunne... | 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 appro... | 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 ma... | 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 t... | 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 i... | 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 benton... | 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 uti... | 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. Variou... | 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... | 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 cyclo... | 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 th... | 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 ... | 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 f... | 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 glacie... | 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 curren... | 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 peb... | 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... | 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 orga... | 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 ... | 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 ... | 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 prot... | 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 ... | 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, causin... | 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 evapor... | 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 t... | 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 ... | 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 or... | 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... | 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... | 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 seafloo... | 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 spec... | 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... | 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 a... | 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 ... | 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 ... | 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 calci... | 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 ... | 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 Pan... | 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 ca... | 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 phenomen... | 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, ... | 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... | 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 spec... | 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 low... | 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 | 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 ... | 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 describ... | 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... | 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 ... | 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 potent... | 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 ... | 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 ... | 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 importan... | 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 projec... | 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 t... | 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 character... | 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 o... | 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 i... | 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... | 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 m... | Hand axe | Wikipedia | 487 | 320336 | https://en.wikipedia.org/wiki/Hand%20axe | Technology | Hand tools | null |
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