text stringlengths 9 3.55k | source stringlengths 31 280 |
|---|---|
The product can simply be discontinued, or it can be sold to another company. Production may shift to the developing countries. Labor costs again play an important role, and the developed countries are busy introducing other products. | https://en.wikipedia.org/wiki/Product_life-cycle_theory |
For instance, the trade pattern shows that the United States and other developed countries have now started importing the product from the developing countries. On costs and revenues: Low production costs and a high demand ensures a longer product life. When production costs are high and demand is low, it is not offere... | https://en.wikipedia.org/wiki/Product_life-cycle_theory |
An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ice formed over a range of years. Cores are drilled with hand augers (for shall... | https://en.wikipedia.org/wiki/Ice_core_dating |
The proportions of different oxygen and hydrogen isotopes provide information about ancient temperatures, and the air trapped in tiny bubbles can be analysed to determine the level of atmospheric gases such as carbon dioxide. Since heat flow in a large ice sheet is very slow, the borehole temperature is another indicat... | https://en.wikipedia.org/wiki/Ice_core_dating |
These data can be combined to find the climate model that best fits all the available data. Impurities in ice cores may depend on location. Coastal areas are more likely to include material of marine origin, such as sea salt ions. | https://en.wikipedia.org/wiki/Ice_core_dating |
Greenland ice cores contain layers of wind-blown dust that correlate with cold, dry periods in the past, when cold deserts were scoured by wind. Radioactive elements, either of natural origin or created by nuclear testing, can be used to date the layers of ice. Some volcanic events that were sufficiently powerful to se... | https://en.wikipedia.org/wiki/Ice_core_dating |
Ice cores have been studied since the early 20th century, and several cores were drilled as a result of the International Geophysical Year (1957–1958). Depths of over 400 m were reached, a record which was extended in the 1960s to 2164 m at Byrd Station in Antarctica. Soviet ice drilling projects in Antarctica include ... | https://en.wikipedia.org/wiki/Ice_core_dating |
An ice core is a vertical column through a glacier, sampling the layers that formed through an annual cycle of snowfall and melt. As snow accumulates, each layer presses on lower layers, making them denser until they turn into firn. Firn is not dense enough to prevent air from escaping; but at a density of about 830 kg... | https://en.wikipedia.org/wiki/Ice_core_dating |
At Summit Camp in Greenland, the depth is 77 m and the ice is 230 years old; at Dome C in Antarctica the depth is 95 m and the age 2500 years. As further layers build up, the pressure increases, and at about 1500 m the crystal structure of the ice changes from hexagonal to cubic, allowing air molecules to move into the... | https://en.wikipedia.org/wiki/Ice_core_dating |
The weight above makes deeper layers of ice thin and flow outwards. Ice is lost at the edges of the glacier to icebergs, or to summer melting, and the overall shape of the glacier does not change much with time. The outward flow can distort the layers, so it is desirable to drill deep ice cores at places where there is... | https://en.wikipedia.org/wiki/Ice_core_dating |
These can be located using maps of the flow lines.Impurities in the ice provide information on the environment from when they were deposited. These include soot, ash, and other types of particle from forest fires and volcanoes; isotopes such as beryllium-10 created by cosmic rays; micrometeorites; and pollen. | https://en.wikipedia.org/wiki/Ice_core_dating |
The lowest layer of a glacier, called basal ice, is frequently formed of subglacial meltwater that has refrozen. It can be up to about 20 m thick, and though it has scientific value (for example, it may contain subglacial microbial populations), it often does not retain stratigraphic information.Cores are often drilled... | https://en.wikipedia.org/wiki/Ice_core_dating |
It can make some snow sublimate, leaving the top inch or so less dense. When the sun approaches its lowest point in the sky, the temperature drops and hoar frost forms on the top layer. Buried under the snow of following years, the coarse-grained hoar frost compresses into lighter layers than the winter snow. As a resu... | https://en.wikipedia.org/wiki/Ice_core_dating |
Ice cores are collected by cutting around a cylinder of ice in a way that enables it to be brought to the surface. Early cores were often collected with hand augers and they are still used for short holes. A design for ice core augers was patented in 1932 and they have changed little since. An auger is essentially a cy... | https://en.wikipedia.org/wiki/Ice_core_dating |
Hand augers can be rotated by a T handle or a brace handle, and some can be attached to handheld electric drills to power the rotation. With the aid of a tripod for lowering and raising the auger, cores up to 50 m deep can be retrieved, but the practical limit is about 30 m for engine-powered augers, and less for hand ... | https://en.wikipedia.org/wiki/Ice_core_dating |
The cuttings (chips of ice cut away by the drill) must be drawn up the hole and disposed of or they will reduce the cutting efficiency of the drill. They can be removed by compacting them into the walls of the hole or into the core, by air circulation (dry drilling), or by the use of a drilling fluid (wet drilling). Dr... | https://en.wikipedia.org/wiki/Ice_core_dating |
The fluid must have a low kinematic viscosity to reduce tripping time (the time taken to pull the drilling equipment out of the hole and return it to the bottom of the hole). Since retrieval of each segment of core requires tripping, a slower speed of travel through the drilling fluid could add significant time to a pr... | https://en.wikipedia.org/wiki/Ice_core_dating |
Historically, there have been three main types of ice drilling fluids: two-component fluids based on kerosene-like products mixed with fluorocarbons to increase density; alcohol compounds, including aqueous ethylene glycol and ethanol solutions; and esters, including n-butyl acetate. Newer fluids have been proposed, in... | https://en.wikipedia.org/wiki/Ice_core_dating |
It uses a string of drill pipe rotated from the top, and drilling fluid is pumped down through the pipe and back up around it. The cuttings are removed from the fluid at the top of the hole and the fluid is then pumped back down. This approach requires long trip times, since the entire drill string must be hoisted out ... | https://en.wikipedia.org/wiki/Ice_core_dating |
Along with the logistical difficulties associated with bringing heavy equipment to ice sheets, this makes traditional rotary drills unattractive. In contrast, wireline drills allow the removal of the core barrel from the drill assembly while it is still at the bottom of the borehole. The core barrel is hoisted to the s... | https://en.wikipedia.org/wiki/Ice_core_dating |
Another alternative is flexible drill-stem rigs, in which the drill string is flexible enough to be coiled when at the surface. This eliminates the need to disconnect and reconnect the pipes during a trip. The need for a string of drillpipe that extends from the surface to the bottom of the borehole can be eliminated b... | https://en.wikipedia.org/wiki/Ice_core_dating |
These cable-suspended drills can be used for both shallow and deep holes; they require an anti-torque device, such as leaf-springs that press against the borehole, to prevent the drill assembly rotating around the drillhead as it cuts the core. The drilling fluid is usually circulated down around the outside of the dri... | https://en.wikipedia.org/wiki/Ice_core_dating |
Some drills have been designed to retrieve a second annular core outside the central core, and in these drills the space between the two cores can be used for circulation. Cable-suspended drills have proved to be the most reliable design for deep ice drilling.Thermal drills, which cut ice by electrically heating the dr... | https://en.wikipedia.org/wiki/Ice_core_dating |
Early thermal drills, designed for use without drilling fluid, were limited in depth as a result; later versions were modified to work in fluid-filled holes but this slowed down trip times, and these drills retained the problems of the earlier models. In addition, thermal drills are typically bulky and can be impractic... | https://en.wikipedia.org/wiki/Ice_core_dating |
Hot-water drills use jets of hot water at the drill head to melt the water around the core. The drawbacks are that it is difficult to accurately control the dimensions of the borehole, the core cannot easily be kept sterile, and the heat may cause thermal shock to the core.When drilling in temperate ice, thermal drills... | https://en.wikipedia.org/wiki/Ice_core_dating |
The casing has to reach down to the impermeable ice layers. To install casing a shallow auger can be used to create a pilot hole, which is then reamed (expanded) until it is wide enough to accept the casing; a large diameter auger can also be used, avoiding the need for reaming. An alternative to casing is to use water... | https://en.wikipedia.org/wiki/Ice_core_dating |
The logistics of any coring project are complex because the locations are usually difficult to reach, and may be at high altitude. The largest projects require years of planning and years to execute, and are usually run as international consortiums. The EastGRIP project, for example, which as of 2017 is drilling in eas... | https://en.wikipedia.org/wiki/Ice_core_dating |
Over the course of a drilling season, scores of people work at the camp, and logistics support includes airlift capabilities provided by the US Air National Guard, using Hercules transport planes owned by the National Science Foundation. In 2015 the EastGRIP team moved the camp facilities from NEEM, a previous Greenlan... | https://en.wikipedia.org/wiki/Ice_core_dating |
With some variation between projects, the following steps must occur between drilling and final storage of the ice core.The drill removes an annulus of ice around the core but does not cut under it. A spring-loaded lever arm called a core dog can break off the core and hold it in place while it is brought to the surfac... | https://en.wikipedia.org/wiki/Ice_core_dating |
The surface that receives the core should be aligned as accurately as possible with the drill barrel to minimise mechanical stress on the core, which can easily break. The ambient temperature is kept well below freezing to avoid thermal shock.A log is kept with information about the core, including its length and the d... | https://en.wikipedia.org/wiki/Ice_core_dating |
The cores are then stored on site, usually in a space below snow level to simplify temperature maintenance, though additional refrigeration can be used. If more drilling fluid must be removed, air may be blown over the cores. Any samples needed for preliminary analysis are taken. | https://en.wikipedia.org/wiki/Ice_core_dating |
The core is then bagged, often in polythene, and stored for shipment. Additional packing, including padding material, is added. When the cores are flown from the drilling site, the aircraft's flight deck is unheated to help maintain a low temperature; when they are transported by ship they must be kept in a refrigerati... | https://en.wikipedia.org/wiki/Ice_core_dating |
Over a depth range known as the brittle ice zone, bubbles of air are trapped in the ice under great pressure. When the core is brought to the surface, the bubbles can exert a stress that exceeds the tensile strength of the ice, resulting in cracks and spall. At greater depths, the air disappears into clathrates and the... | https://en.wikipedia.org/wiki/Ice_core_dating |
Some steps can be taken to alleviate the problem. Liners can be placed inside the drill barrel to enclose the core before it is brought to the surface, but this makes it difficult to clean off the drilling fluid. In mineral drilling, special machinery can bring core samples to the surface at bottom-hole pressure, but t... | https://en.wikipedia.org/wiki/Ice_core_dating |
Keeping the processing facilities at very low temperatures limits thermal shocks. Cores are most brittle at the surface, so another approach is to break them into 1 m lengths in the hole. Extruding the core from the drill barrel into a net helps keep it together if it shatters. Brittle cores are also often allowed to r... | https://en.wikipedia.org/wiki/Ice_core_dating |
Many different kinds of analysis are performed on ice cores, including visual layer counting, tests for electrical conductivity and physical properties, and assays for inclusion of gases, particles, radionuclides, and various molecular species. For the results of these tests to be useful in the reconstruction of palaeo... | https://en.wikipedia.org/wiki/Ice_core_dating |
Another method is to correlate radionuclides or trace atmospheric gases with other timescales such as periodicities in the earth's orbital parameters.A difficulty in ice core dating is that gases can diffuse through firn, so the ice at a given depth may be substantially older than the gases trapped in it. As a result, ... | https://en.wikipedia.org/wiki/Ice_core_dating |
At locations with very low snowfall, such as Vostok, the uncertainty in the difference between ages of ice and gas can be over 1,000 years.The density and size of the bubbles trapped in ice provide an indication of crystal size at the time they formed. The size of a crystal is related to its growth rate, which in turn ... | https://en.wikipedia.org/wiki/Ice_core_dating |
The CO2 can be isolated by subliming the ice in a vacuum, keeping the temperature low enough to avoid the loess giving up any carbon. The results have to be corrected for the presence of 14C produced directly in the ice by cosmic rays, and the amount of correction depends strongly on the location of the ice core. Corre... | https://en.wikipedia.org/wiki/Ice_core_dating |
Carbon in particulates can also be dated by separating and testing the water-insoluble organic components of dust. The very small quantities typically found require at least 300 g of ice to be used, limiting the ability of the technique to precisely assign an age to core depths.Timescales for ice cores from the same he... | https://en.wikipedia.org/wiki/Ice_core_dating |
The Laschamp event, a geomagnetic reversal about 40,000 years ago, can be identified in cores; away from that point, measurements of gases such as CH4 (methane) can be used to connect the chronology of a Greenland core (for example) with an Antarctic core. In cases where volcanic tephra is interspersed with ice, it can... | https://en.wikipedia.org/wiki/Ice_core_dating |
Another approach is to use Bayesian probability techniques to find the optimal combination of multiple independent records. This approach was developed in 2010 and has since been turned into a software tool, DatIce.The boundary between the Pleistocene and the Holocene, about 11,700 years ago, is now formally defined wi... | https://en.wikipedia.org/wiki/Ice_core_dating |
Cores show visible layers, which correspond to annual snowfall at the core site. If a pair of pits is dug in fresh snow with a thin wall between them and one of the pits is roofed over, an observer in the roofed pit will see the layers revealed by sunlight shining through. A six-foot pit may show anything from less tha... | https://en.wikipedia.org/wiki/Ice_core_dating |
When this turns to ice, the two layers will make up no more than a foot of ice. The layers corresponding to the summer snow will contain bigger bubbles than the winter layers, so the alternating layers remain visible, which makes it possible to count down a core and determine the age of each layer. As the depth increas... | https://en.wikipedia.org/wiki/Ice_core_dating |
Dust layers may now become visible. Ice from Greenland cores contains dust carried by wind; the dust appears most strongly in late winter, and appears as cloudy grey layers. | https://en.wikipedia.org/wiki/Ice_core_dating |
These layers are stronger and easier to see at times in the past when the earth's climate was cold, dry, and windy.Any method of counting layers eventually runs into difficulties as the flow of the ice causes the layers to become thinner and harder to see with increasing depth. The problem is more acute at locations wh... | https://en.wikipedia.org/wiki/Ice_core_dating |
Identification of these layers, both visually and by measuring density of the core against depth, allows the calculation of a melt-feature percentage (MF): an MF of 100% would mean that every year's deposit of snow showed evidence of melting. MF calculations are averaged over multiple sites or long time periods in orde... | https://en.wikipedia.org/wiki/Ice_core_dating |
The isotopic composition of the oxygen in a core can be used to model the temperature history of the ice sheet. Oxygen has three stable isotopes, 16O, 17O and 18O. The ratio between 18O and 16O indicates the temperature when the snow fell. Because 16O is lighter than 18O, water containing 16O is slightly more likely to... | https://en.wikipedia.org/wiki/Ice_core_dating |
At lower temperatures, the difference is more pronounced. The standard method of recording the 18O/16O ratio is to subtract the ratio in a standard known as standard mean ocean water (SMOW): δ 18 O = ( ( 18 O 16 O ) s a m p l e ( 18 O 16 O ) S M O W − 1 ) × 1000 o / o o , {\displaystyle \mathrm {\delta ^{18}O} ={\Biggl... | https://en.wikipedia.org/wiki/Ice_core_dating |
Combining the δ18O measurements of an ice core sample with the borehole temperature at the depth it came from provides additional information, in some cases leading to significant corrections to the temperatures deduced from the δ18O data. Not all boreholes can be used in these analyses. If the site has experienced sig... | https://en.wikipedia.org/wiki/Ice_core_dating |
Deuterium (2H, or D) is heavier than hydrogen (1H) and makes water more likely to condense and less likely to evaporate. A δD ratio can be defined in the same way as δ18O. | https://en.wikipedia.org/wiki/Ice_core_dating |
There is a linear relationship between δ18O and δD: δ D = 8 × δ 18 O + d , {\displaystyle \mathrm {\delta D} =8\times \mathrm {\delta ^{18}O} +\mathrm {d} ,} where d is the deuterium excess. It was once thought that this meant it was unnecessary to measure both ratios in a given core, but in 1979 Merlivat and Jouzel sh... | https://en.wikipedia.org/wiki/Ice_core_dating |
It was understood in the 1960s that analyzing the air trapped in ice cores would provide useful information on the paleoatmosphere, but it was not until the late 1970s that a reliable extraction method was developed. Early results included a demonstration that the CO2 concentration was 30% less at the last glacial maxi... | https://en.wikipedia.org/wiki/Ice_core_dating |
N2O (nitrous oxide) levels are also correlated with glacial cycles, though at low temperatures the graph differs somewhat from the CO2 and CH4 graphs. Similarly, the ratio between N2 (nitrogen) and O2 (oxygen) can be used to date ice cores: as air is gradually trapped by the snow turning to firn and then ice, O2 is los... | https://en.wikipedia.org/wiki/Ice_core_dating |
Gravity causes heavier molecules to be enriched at the bottom of a gas column, with the amount of enrichment depending on the difference in mass between the molecules. Colder temperatures cause heavier molecules to be more enriched at the bottom of a column. These fractionation processes in trapped air, determined by t... | https://en.wikipedia.org/wiki/Ice_core_dating |
Summer snow in Greenland contains some sea salt, blown from the surrounding waters; there is less of it in winter, when much of the sea surface is covered by pack ice. Similarly, hydrogen peroxide appears only in summer snow because its production in the atmosphere requires sunlight. These seasonal changes can be detec... | https://en.wikipedia.org/wiki/Ice_core_dating |
Dragging them down the length of the core, and recording the conductivity at each point, gives a graph that shows an annual periodicity. Such graphs also identify chemical changes caused by non-seasonal events such as forest fires and major volcanic eruptions. When a known volcanic event, such as the eruption of Laki i... | https://en.wikipedia.org/wiki/Ice_core_dating |
Material from Laki can be identified in Greenland ice cores, but did not spread as far as Antarctica; the 1815 eruption of Tambora in Indonesia injected material into the stratosphere, and can be identified in both Greenland and Antarctic ice cores. If the date of the eruption is not known, but it can be identified in ... | https://en.wikipedia.org/wiki/Ice_core_dating |
There are also more ancient reference points, such as the eruption of Toba about 72,000 years ago.Many other elements and molecules have been detected in ice cores. In 1969, it was discovered that lead levels in Greenland ice had increased by a factor of over 200 since pre-industrial times, and increases in other eleme... | https://en.wikipedia.org/wiki/Ice_core_dating |
Methanesulfonate (MSA) (CH3SO−3) is produced in the atmosphere by marine organisms, so ice core records of MSA provide information on the history of the oceanic environment. Both hydrogen peroxide (H2O2) and formaldehyde (HCHO) have been studied, along with organic molecules such as carbon black that are linked to vege... | https://en.wikipedia.org/wiki/Ice_core_dating |
In some cases there are contributions from more than one source to a given species: for example, Ca++ comes from dust as well as from marine sources; the marine input is much greater than the dust input and so although the two sources peak at different times of the year, the overall signal shows a peak in the winter, w... | https://en.wikipedia.org/wiki/Ice_core_dating |
Galactic cosmic rays produce 10Be in the atmosphere at a rate that depends on the solar magnetic field. The strength of the field is related to the intensity of solar radiation, so the level of 10Be in the atmosphere is a proxy for climate. Accelerator mass spectrometry can detect the low levels of 10Be in ice cores, a... | https://en.wikipedia.org/wiki/Ice_core_dating |
Meteorites and micrometeorites that land on polar ice are sometimes concentrated by local environmental processes. For example, there are places in Antarctica where winds evaporate surface ice, concentrating the solids that are left behind, including meteorites. Meltwater ponds can also contain meteorites. At the South... | https://en.wikipedia.org/wiki/Ice_core_dating |
These have been collected by a robotic "vacuum cleaner" and examined, leading to improved estimates of their flux and mass distribution. The well is not an ice core, but the age of the ice that was melted is known, so the age of the recovered particles can be determined. | https://en.wikipedia.org/wiki/Ice_core_dating |
The well becomes about 10 m deeper each year, so micrometeorites collected in a given year are about 100 years older than those from the previous year. Pollen, an important component of sediment cores, can also be found in ice cores. It provides information on changes in vegetation. | https://en.wikipedia.org/wiki/Ice_core_dating |
In addition to the impurities in a core and the isotopic composition of the water, the physical properties of the ice are examined. Features such as crystal size and axis orientation can reveal the history of ice flow patterns in the ice sheet. The crystal size can also be used to determine dates, though only in shallo... | https://en.wikipedia.org/wiki/Ice_core_dating |
In 1841 and 1842, Louis Agassiz drilled holes in the Unteraargletscher in the Alps; these were drilled with iron rods and did not produce cores. The deepest hole achieved was 60 m. On Erich von Drygalski's Antarctic expedition in 1902 and 1903, 30 m holes were drilled in an iceberg south of the Kerguelen Islands and te... | https://en.wikipedia.org/wiki/Ice_core_dating |
Similar devices are in use today, modified to allow sampling to a depth of about 9 m. They are simply pushed into the snow and rotated by hand.The first systematic study of snow and firn layers was by Ernst Sorge, who was part of the Alfred Wegener Expedition to central Greenland in 1930–1931. Sorge dug a 15 m pit to e... | https://en.wikipedia.org/wiki/Ice_core_dating |
Three other expeditions in the 1950s began ice coring work: a joint Norwegian-British-Swedish Antarctic Expedition (NBSAE), in Queen Maud Land in Antarctica; the Juneau Ice Field Research Project (JIRP), in Alaska; and Expéditions Polaires Françaises, in central Greenland. Core quality was poor, but some scientific wor... | https://en.wikipedia.org/wiki/Ice_core_dating |
In Antarctica, a 307 m core was drilled at Byrd Station in 1957–1958, and a 264 m core at Little America V, on the Ross Ice Shelf, the following year. The success of the IGY core drilling led to increased interest in improving ice coring capabilities, and was followed by a CRREL project at Camp Century, where in the ea... | https://en.wikipedia.org/wiki/Ice_core_dating |
Soviet ice drilling projects began in the 1950s, in Franz Josef Land, the Urals, Novaya Zemlya, and at Mirny and Vostok in the Antarctic; not all these early holes retrieved cores. Over the following decades work continued at multiple locations in Asia. Drilling in the Antarctic focused mostly on Mirny and Vostok, with... | https://en.wikipedia.org/wiki/Ice_core_dating |
The first deep hole at Vostok reached 506.9 m in April 1970; by 1973 a depth of 952 m had been reached. A subsequent hole, Vostok 2, drilled from 1971 to 1976, reached 450 m, and Vostok 3 reached 2202 m in 1985 after six drilling seasons. Vostok 3 was the first core to retrieve ice from the previous glacial period, 150... | https://en.wikipedia.org/wiki/Ice_core_dating |
Drilling was interrupted by a fire at the camp in 1982, but further drilling began in 1984, eventually reaching 2546 m in 1989. A fifth Vostok core was begun in 1990, reached 3661 m in 2007, and was later extended to 3769 m. The estimated age of the ice is 420,000 years at 3310 m depth; below that point it is difficult... | https://en.wikipedia.org/wiki/Ice_core_dating |
The Dome C core had very low accumulation rates, which mean that the climate record extended a long way; by the end of the project the usable data extended to 800,000 years ago.Other deep Antarctic cores included a Japanese project at Dome F, which reached 2503 m in 1996, with an estimated age of 330,000 years for the ... | https://en.wikipedia.org/wiki/Ice_core_dating |
A 948 m core was drilled at Berkner Island by a project managed by the British Antarctic Survey from 2002 to 2005, extending into the last glacial period; and an Italian-managed ITASE project completed a 1620 m core at Talos Dome in 2007.In 2016, cores were retrieved from the Allan Hills in Antarctica in an area where ... | https://en.wikipedia.org/wiki/Ice_core_dating |
In 1970, scientific discussions began which resulted in the Greenland Ice Sheet Project (GISP), a multinational investigation into the Greenland ice sheet that lasted until 1981. Years of field work were required to determine the ideal location for a deep core; the field work included several intermediate-depth cores, ... | https://en.wikipedia.org/wiki/Ice_core_dating |
Two holes, 30 km apart, were eventually drilled at the north-central location in the early 1990s by two groups: GRIP, a European consortium, and GISP-2, a group of US universities. GRIP reached bedrock at 3029 m in 1992, and GISP-2 reached bedrock at 3053 m the following year. Both cores were limited to about 100,000 y... | https://en.wikipedia.org/wiki/Ice_core_dating |
Drilling began in 1996; the first hole had to be abandoned at 1400 m in 1997, and a new hole was begun in 1999, reaching 3085 m in 2003. The hole did not reach bedrock, but terminated at a subglacial river. The core provided climatic data back to 123,000 years ago, which covered part of the last interglacial period. | https://en.wikipedia.org/wiki/Ice_core_dating |
The subsequent North Greenland Eemian (NEEM) project retrieved a 2537 m core in 2010 from a site further north, extending the climatic record to 128,500 years ago; NEEM was followed by EastGRIP, which began in 2015 in east Greenland and was planned to be completed in 2020. In March 2020, the 2020 EGRIP field campaign w... | https://en.wikipedia.org/wiki/Ice_core_dating |
Ice cores have been drilled at locations away from the poles, notably in the Himalayas and the Andes. Some of these cores reach back to the last glacial period, but they are more important as records of El Niño events and of monsoon seasons in south Asia. Cores have also been drilled on Mount Kilimanjaro, in the Alps, ... | https://en.wikipedia.org/wiki/Ice_core_dating |
IPICS (International Partnerships in Ice Core Sciences) has produced a series of white papers outlining future challenges and scientific goals for the ice core science community. These include plans to: Retrieve ice cores that reach back over 1.2 million years, in order to obtain multiple iterations of ice core record ... | https://en.wikipedia.org/wiki/Ice_core_dating |
Identify additional proxies from ice cores, for example for sea ice, marine biological productivity, or forest fires. Drill additional cores to provide high-resolution data for the last 2,000 years, to use as input for detailed climate modelling. Identify an improved drilling fluid Improve the ability to handle brittle... | https://en.wikipedia.org/wiki/Ice_core_dating |
Prehistoric archaeology is a subfield of archaeology, which deals specifically with artefacts, civilisations and other materials from societies that existed before any form of writing system or historical record. Often the field focuses on ages such as the Stone Age, Bronze Age and Iron Age, although it also encompasse... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
Prehistoric archaeology is also sometimes termed as anthropological archaeology because of its indirect traces with complex patterns. Due to the unique nature of prehistoric archaeology, in that written records can not be drawn upon to aid the study of the societies it focuses on, the subject matter investigated is ent... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
The subfield has existed since at least the late 1820s or early 1830s and is now a fully recognised and separate field of archaeology. Other fields of archaeology include; Classical archaeology, Near Eastern archaeology - as known as Biblical archaeology, Historical archaeology, Underwater archaeology and many more, ea... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
As such, there are many excavations attributed to this field which have occurred and are occurring all over the world to uncover all different types of settlements and civilisations. Without history to provide evidence for names, places and motivations, prehistoric archaeologists speak in terms of cultures which can on... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
Prehistoric archaeology, as with many other fields of archaeology, is attributed to multiple different individuals therefore an accurate and definitive timeline for its creation is difficult to present. The origins of prehistoric archaeology were marked by treasure hunting also known as antiquarianism and the individua... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
Beyond that, there are three other individuals who represented different field schools who are thought to have begun the first excavations dedicated solely to the study of prehistoric archaeology at roughly the same time between the 1820s to 1830s. Boucher de Perthes – a French archaeologist leading the Abbeville field... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
Several examples, though not a complete list of every country, are listed below by continental area. Within Europe exploration began in England with several individuals such as amateur archaeologist William Pengelly who studied the Kent Cavern in approximately 1846, and within Turkey excavation into specifically prehis... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
In North America exploration began in the United States in the mid-1800s with the collective excavation interests being led by the works of the American Philosophical Society, the American Antiquarian Society, and the Smithsonian Institution and in Canada excavations started in 1935 though it was not until 1965 that it... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
The purpose of prehistoric archaeology is to explore and understand civilisations that existed before writing systems; including the Stone, Bronze and Iron Age societies across the world. Within its early origins prehistoric archaeology had a focus on gathering artefacts and treasures to display in museums and private ... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
There are multitudes of credible past and emerging prehistoric archaeologists who have dedicated time and effort into honing their craft in order to accurately understand the lives of the individuals and societies they are studying. Some of the important foundational archaeologists are; Daniel Wilson – a Scottish-born ... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
More modern archaeologists, including Ali Umut Türkcan – who directed the excavations at Çatalhöyük as of 2022, have helped to further these developments in the field by directing excavations and studying materials found within the sites. Other modern archaeologists include; Paul Bahn – a British archaeologist who stud... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
Some of the main types of sites include early proto-city and proto city-states, settlements, temples and sanctuaries of worship and cave sites. To define each of these terms archaeologically; a proto city-state is a large town or village that existed in the Neolithic era, it is also categorised by its lack of central r... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
All prehistoric archaeology sites must contain evidence of humans – even if they did not actively live on the site or visited it occasionally, and a lack of historical record within the society. Sites that feature the ability of the inhabitants to record information about themselves are not considered prehistoric. Preh... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
The period in which prehistoric archaeology covers is most often the Stone, Bronze and Iron ages, within each of these ages periods such as the Neolithic within the Stone age are explored deeply. In Western Europe the prehistoric period ends with Roman colonisation in 43 AD, with some non-Romanised areas the period doe... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
Archaeologists use many different methods to research the artefacts and materials that may be found during an excavation. Within early excavations dedicated to treasure hunting little to no care was taken when removing soil covering artefacts or when removing the artefacts and materials themselves from sites which may ... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
Within aerial photography several important markers of archaeological sites can be revealed such as; shadow marks, crop marks and soil marks. Archaeologists also use a range of techniques when excavating a site to uncover materials including; digging test pits, creating trenches and using the box-grid or quadrant metho... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
There are a vast amount of difficulties faced within prehistoric archaeology including; site degradation, which makes understanding a site very difficult as it erases evidence that may have been useful for gaining insight into the civilisation. Degradation of a site may be exacerbated by climate change as often prehist... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
It is because of these gaps that in order to understand the physical evidence that has been recovered prehistoric archaeologists, as well as their counterparts in the sibling fields of archaeology, must make educated guesses as to what is there and what should be there based on the finds that they have. The variety of ... | https://en.wikipedia.org/wiki/Prehistoric_archaeology |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.