# data[].attributes.body
Lightly compressed mass of plant remains. p149

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geographic coordinate that specifies the north–south position of a point on the Earth's surface

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geographic coordinate that specifies the east–west position of a point on the Earth's surface.

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each layer of rock is older than the layer above it and younger than the rock layer below it.

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the process whereby organisms better adapted to their environment tend to survive and produce more offspring.

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the change in the characteristics of a species over several generations and relies on the process of natural selection

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The theory of evolution is based on the idea that all species are related and gradually change over time.

Evolution relies on there being genetic variation in a population which affects the physical characteristics (phenotype) of an organism.

Some of these characteristics may give the individual an advantage over other individuals which they can then pass on to their offspring.

What is natural selection?

Charles Darwin's theory of evolution states that evolution happens by natural selection.

Individuals in a species show variation in physical characteristics. This variation is because of differences in their genes.

Individuals with characteristics best suited to their environment are more likely to survive, finding food, avoiding predators and resisting disease. These individuals are more likely to reproduce and pass their genes on to their children.

Individuals that are poorly adapted to their environment are less likely to survive and reproduce. Therefore their genes are less likely to be passed on to the next generation.

As a consequence those individuals most suited to their environment survive and, given enough time, the species will gradually evolve.

Natural selection in action: the Peppered moth

Before the industrial revolution in the mid-1700s, the peppered moth was most commonly a pale whitish colour with black spots.

This colouring enabled them to hide from potential predators on trees with pale-coloured bark, such as birch trees.

The rarer dark-coloured peppered moths were easily seen against the pale bark of trees and therefore more easily seen by predators.

As the Industrial Revolution reached its peak, the air in industrial areas became full of soot. This stained trees and buildings black.

As a result, the lighter moths became much easier to spot than the darker ones, making them vulnerable to being eaten by birds.

The darker moths were now camouflaged against the soot-stained trees and therefore less likely to be eaten.

Over time this change in the environment led to the darker moths becoming more common and the pale moths rarer.

What have genes got to do with it?

The mechanisms of evolution operate at the genomic level. Changes in DNA sequences affect the composition and expression of our genes, the basic units of inheritance.

To understand how different species have evolved we have to look at the DNA sequences in their genomes.

Our evolutionary history is written into our genome. The human genome looks the way it does because of all the genetic changes that affected our ancestors.

When DNA and genes in different species look very similar, this is usually taken as evidence of them sharing ancestors.

For example, humans and the fruit fly, Drosophila melanogaster, share much of their DNA. 75 per cent of genes that cause diseases in humans are also found in the fruit fly.

DNA accumulates changes over time. Some of these changes can be beneficial, and provide a selective advantage for an organism.

Other changes may be harmful if they affect an important, everyday function. As a result some genes do not change much. They are said to be conserved.

Different types of evolution
Convergent evolution

When the same adaptations evolve independently, under similar selection pressures.

For example, flying insects, birds and bats have all evolved the ability to fly, but independently of each other.

Co-evolution

When two species or groups of species have evolved alongside each other where one adapts to changes in the other.

For example, flowering plants and pollinating insects such as bees.

Adaptive radiation

When a species splits into a number of new forms when a change in the environment makes new resources available or creates new environmental challenges.

For example, finches on the Galapagos Islands have developed different shaped beaks to take advantage of the different kinds of food available on different islands.

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In biology, evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection.

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the termination of an organism or of a group of organisms (taxon), usually a species

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Radiocarbon dating is essentially a method designed to measure residual radioactivity

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What is Radiocarbon Dating?

Radiocarbon dating is a method of what is known as "Absolute Dating". Despite the name, it does not give an absolute date of organic material - but an approximate age, usually within a range of a few years either way. The other method is "Relative Dating" which gives an order of events without giving an exact age (1): typically artefact typology or the study of the sequence of the evolution of fossils.

There are three carbon isotopes that occur as part of the Earth's natural processes; these are carbon-12, carbon-13 and carbon-14. The unstable nature of carbon 14 (with a precise half-life that makes it easy to measure) means it is ideal as an absolute dating method. The other two isotopes in comparison are more common than carbon-14 in the atmosphere but increase with the burning of fossil fuels making them less reliable for study (2); carbon-14 also increases, but its relative rarity means its increase is negligible. The half-life of the ¹⁴C isotope is 5,730 years, adjusted from 5,568 years originally calculated in the 1940s; the upper limit of dating is in the region of 55-60,000 years, after which the amount of ¹⁴C is negligible (3). After this point, other Absolute Dating methods may be used.

Today, the radiocarbon-14 dating method is used extensively in environmental sciences and in human sciences such as archaeology and anthropology. It also has some applications in geology; its importance in dating organic materials cannot be underestimated enough. In 1979, Desmond Clark said of the method "we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation" (3).

Radiocarbon dating may only be used on organic materials. Typically (6):

Wood and charcoal

Seeds, spores and pollen

Bone, leather, hair, fur, horn and blood residue

Peat, mud and soil

Shells, coral and chitin

Pottery (where there is organic residue)

Wall paintings (as they usually contain organic material such as crushed fruit and insects)

Paper and parchment

The above list is not exhaustive; most organic material is suitable so long as it is of sufficient age and has not mineralised - dinosaur bones are out as they no longer have any carbon left. Stone and metal cannot be dated but pottery may be dated through surviving residue such as food particles or paint that uses organic material (8).

There are a number of ways to enter into a career in studying radiocarbon dating. Typically, a Master's Degree in chemistry is required because of the extensive lab work. Increasingly though, students are learning about the principles of radiocarbon dates in archaeology, palaeontology and climate science degrees and can combine cross-disciplinary studies.

History of Radiocarbon-14 Dating

The method developed in the 1940's and was a ground-breaking piece of research that would change dating methods forever. A team of researchers led by Willard F. Libby calculated the rate of radioactive decay of the ¹⁴C isotope (4) in carbon black powder. As a test, the team took samples of acacia wood from two Egyptian Pharaohs and dated them; the results came back to within what was then a reasonable range: 2800BC +/- 250 years whereas the earlier independent dates (largely the dendrochronology records) were 2625 +/- 75 years (3), (5). Archaeologists had used Relative Dating methods to calculate their reigns. Though their initial calculations were slightly incorrect thanks to the contaminants of extensive nuclear testing of the age, scientists soon discovered the error and developed methods that were more accurate, including a date of calibration to 1950. This new method was based on gas and liquid scintillation counting and these methods are still used today, having been demonstrated as more accurate than Libby's original method (3). Willard Libby would receive a Nobel Prize for Chemistry in 1960.

The next big step in the radiocarbon dating method would be Accelerated Mass Spectrometry which was developed in the late 1980s and published its first results in 1994 (3). This was a giant leap forward in that it offered far more accurate dates for a far smaller sample (9); this made destruction of samples a far less delicate issue to researchers, especially on artefacts such as The Shroud of Turin for which accurate dates were now possible without damaging a significant part of the artefact. AMS counts the quantity of ¹⁴ C in a sample rather than waiting for the isotope to decay; this also means greater accuracy readings for older dates.

How it Works

The ¹⁴C isotope is constantly formed in the upper atmosphere thanks to the effects of cosmic rays on nitrogen-14 atoms. It is oxidised quickly and absorbed in great quantities by all living organisms - animal and plant, land and ocean dwelling alike. When an organism dies, it stops absorbing the radioactive isotope and immediately starts decaying (7). As previously mentioned, the half life of the ¹⁴C isotope is 5,730 years - this means that it takes 5,730 years to reach half the radioactivity that the organism had at the point of death, another 5,730 years to reach 25% radioactivity it had at the point of death and so on. Radiocarbon dating is simply a measure of the level of ¹⁴C isotope within the organic remains (8). This is not as clear-cut as it seems as the amount of ¹⁴ C isotopes in the atmosphere can vary. This is why calibration against objects whose age is known is required (14).

AMS works slightly differently; it converts the atoms of the sample into fast-moving ions so that they become charged atoms. By applying magnetic and electrical fields, the mass of these ions is measured and the accelerator is used to remove ions that might contaminate the dating. The sample passes through several accelerators in order to remove as many atoms as possible until the ¹⁴C and some ¹²C and ¹³C pass into the detector. These latter atoms are used as part of the calibration process to measure the relative number of isotopes (9).

How is a Date Calibrated?

When the half-life was corrected in 1950, the year was taken as a base date from which to calculate all resulting dates. Therefore, any expression of "before present" will mean "before 1950". It is presumed that the proportion of atmospheric ¹⁴C is the same today as it was in 1950 (10), (11) and that the half-life remains the same. If a radioactivity level comes back as half of what would have been expected if the organism had died in 1950, then it is presumed to be 5,730 years before 1950. This does not mean that we have a precise year of 3780BC, it means we then need to calibrate through other methods that will show us how atmospheric concentrations of the ¹⁴C isotope has changed - most typically through the dendrochronology records (tree ring data) (10). Very old trees such as North American Bristlecone Pine are ideal for constructing long and accurate records of the state of the atmosphere. This allows researchers to account for variation by comparing the known records of ¹⁴C levels in the tree record, looking for a tree record that has the same proportion of radiocarbon. The overlapping nature of the tree records means this is the most accurate record we have. There will of course be several possible calendar years within the expected range, which is why radiocarbon dates come with a variation such as +/- 25 years for example (11).

Radiocarbon-14 Dating in Action

Archaeology was one of the first, and remains the major, disciplines to use radiocarbon dating and this is why many enter into the lab through combining chemistry and archaeological studies. It has a greater impact on our understanding of the human past than in any other field.

Radiocarbon dating is profoundly useful in archaeology, especially since the dawn of the even more accurate AMS method when more accurate dates could be obtained for smaller sample sizes. One good example is a critical piece of research into the diet of the fragile Viking colonies of Greenland (13) for example; the study examined not just the ¹⁴C dates of the people in the graves, but was also in examining their diet through examining the carbon isotopes themselves. The study concluded dates that were already suspected but not confirmed: that the colony was occupied between the late 10 th century and the early 12 th century. Radiocarbon AMS was also used to calculate when the last Vikings departed Greenland (17).

There has been much debate about the age of The Shroud of Turin. It has become an important relic for many Catholics. The debate raged on for the decades after its discovery. Experts pointed to its medieval design, depiction of Christ and several other key factors marking it as in the region of 700 years old. It wasn't until 1988, and several subsequent tests since then, that this was confirmed (14); it is now the best-known example of the success of the AMS method as countless tests have been carried out and confirmed the dates. A significant portion of the Shroud would have been destroyed using the older method. The paper for the 1988 study is available online (15). Each subsequent test has come back with dates of the mid 14 th century.

Landscape Archaeology is a bridge between archaeology and environmental sciences though many consider it an environmental science in its own right. It is the study of how people in the past exploited and changed the environment around them. Typically, this will involve examining spores and pollen to examine when land was cleared of scrub and trees in the Neolithic Revolution to make way for crops. It also makes use of phytoliths, entomological remains, GIS (digital mapping), soil sampling, bone analyses, ground penetrating radar, and map studies and other documentary data. It has been fundamental, especially in Europe, to demonstrating how landscapes are relics and monuments in themselves and are worthy of study as such. Returning to the example of the Vikings in Greenland above, the extended study and dating of the faunal remains shows distinct changes that were made by the Vikings. The studies show the approximate date of arrival of European livestock and crops (13) and when these finally disappeared from the record (17). Studies such as this are fundamental to determining not just how the environment has changed thanks to human manipulation, but also to natural changes due to fluctuations in the environment and climate.

The practical uses of radiocarbon dating in climate science covers similar examples to the archaeological examples seen above (changes in fauna and vegetation for example) but it is fundamental in other areas too (12). Most critically, it is used when studying ice core date in determining the composition of the climate of the past. Many hundreds of ice samples have been taken in Antarctica and this is fundamental to understanding how we are changing the climate today, and how it may change in future when accounting for fluctuations in atmospheric carbon (18). There are complications however and researchers check the known ice records against any new samples, taking into consideration known ice dates in factoring in their margin of error. Atmospheric composition, the amount of ice coverage at a given time... all of these factors are important in examining past climates (19).

Phytolith studies (fossilised plant remains), entomology (study of insects) as well as the previously mentioned studies of pollen and spores can not only show how an environment changed and what caused it (human engineering or environmental change), but also when the changes occurred.

Sources

http://paleobiology.si.edu/geotime/main/foundation_dating2.html

http://www.skepticalscience.com/history-climate-science.html

http://www.c14dating.com/int.html

http://www.physics.arizona.edu/ams/education/rcarbon_history.htm

http://hbar.phys.msu.ru/gorm/fomenko/libby.htm http://www.sciencemag.org/content/110/2869/678

http://www.radiocarbon.com/about-carbon-dating.htm

http://www.c14dating.com/k12.html

https://c14.arch.ox.ac.uk/embed.php?File=dating.html

https://c14.arch.ox.ac.uk/embed.php?File=ams.html

https://c14.arch.ox.ac.uk/embed.php?File=calibration.html

http://www.c14dating.com/agecalc.html

http://www.aip.org/history/climate/Radioc.htm

Arneborg, J., Heinemeier, J., Lynnerup, N., Nielsen, H.L., Rud, N., Sveinbjörnsdóttir, A. E.: 1999: CHANGE OF DIET OF THE GREENLAND VIKINGS DETERMINED FROM STABLE CARBON ISOTOPE ANALYSIS AND 14C DATING OF THEIR BONES. Radiocarbon 41 (2): p157-168 (http://natmus.dk/fileadmin/user_upload/natmus/forskning/dokumenter/SILA/Projects/radiocarbon.pdf)

http://nvlpubs.nist.gov/nistpubs/jres/109/2/j92cur.pdf

shroud.com/nature.htm

Erika Martin Seibert. "Archaeology and Landscape" (http://www.nps.gov/nr/publications/guidance/NR_workshop_3-11-09/Archeol_and_landscapes_Erika.doc)

Arneborg, J., Heinemeier, J., Lynnerup, N., Nielsen, H. L., Rud, N., Sveinbjornsdottir, A.E., 2002: C-14 dating and the disappearance of Norsemen from Greenland. Europhysics News 33 (3), 77-80 (http://www.europhysicsnews.org/articles/epn/pdf/2002/03/epn02301.pdf)

https://journals.uair.arizona.edu/index.php/radiocarbon/article/viewFile/1487/1491

http://onlinelibrary.wiley.com/doi/10.1029/2009JD011860/full

# data[].attributes.attachment_link.description
Radiocarbon dating is a method of what is known as "Absolute Dating". Despite the name, it does not give an absolute date of organic material - but an approximate age, usually within a range of a few years either way.

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layers of sediment are originally deposited horizontally under the action of gravity.

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The Principle of Original Horizontality was proposed by the Danish geological pioneer Nicholas Steno (1638-1686). This principle states that layers of sediment are originally deposited horizontally under the action of gravity. The principle is important to the analysis of folded and tilted strata.

From these observations is derived the conclusion that the Earth has not been static and that great forces have been at work over long periods of time, further leading to the conclusions of the science of plate tectonics; that movement and collisions of large plates of the Earth's crust is the cause of folded strata.

As one of Steno's Laws, the Principle of Original Horizontality served well in the nascent days of geological science. However, it is now known that not all sedimentary layers are deposited purely horizontally.

For instance, coarser grained sediments such as sand may be deposited at angles of up to 15 degrees, held up by the internal friction between grains which prevents them slumping to a lower angle without additional reworking or effort. This is known as the angle of repose, and a prime example is the surface of sand dunes.

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The Principle of Original Horizontality was proposed by the Danish geological pioneer Nicholas Steno (1638-1686). This principle states that layers of sediment are originally deposited horizontally under the action of gravity. The principle is important to the analysis of folded and tilted strata.

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the surface of a division between parallel rock strata, indicating interruption of sedimentation: a type of unconformity.

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the forms of life which existed during limited periods of geologic time and thus are used as guides to define periods of geologic time

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Eon: Eon, Long span of geologic time. In formal usage, eons are the longest portions of geologic time (eras are the second-longest). Three eons are recognized: the Phanerozoic Eon (dating from the present back to the beginning of the Cambrian Period), the Proterozoic Eon, and the Archean Eon. Less

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a major division of time that is a subdivision of an eon and is itself subdivided into periods.

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Subdivision of a geologic era

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A subdivision of a geological period on the geological time scale.

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Age of Invertebrates 543-290 Million years ago

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Volcanic rock formed at the Earth's surface (cooled lava). These rocks cool and solidify quickly to form small crystals.

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Volcanic rock that cools and solidify within Earth's surface. These rocks cool slowly and allow for large crystal formation.

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An intrusive volcanic rock that forms as a result of magma squeezing into a crevice or crack

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Magma that reaches Earth's surface (p 200)

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A type of magma that is rich in silica and aluminum that forms light-colored igneous rock containing minerals such as quartz and feldspar.

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Type of magma rich in iron and magnesium. Forms dark-colored igneous rock containing minerals such as hornblende, augite, and biotite.

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Process by which sediments are compacted under pressure to become sedimentary rocks.

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Clastic sedimentary rocks are made up of pieces of other rocks

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Sedimentary rock whose sediment is made of plants and animals or fossils
.
Examples include limestone and coal.

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A void within a rock, which can contain air, water, hydrocarbons or other fluids. In a rock, the percentage of pore space is the porosity.

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Process by which a sediment progressively loses its porosity due to the effects of loading.

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Lightly compressed mass of plant remains. p149

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Any rock composed mainly of carbonate minerals. The principal members of the group are the sedimentary rocks dolomite and limestone

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A change in the type of sediment being laid down. The arrangement of visible layers. Bedding planes (lines between different layers) are usually horizontal.

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The remains, impression, or any other evidence of a plant or animal preserved in rock.

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Process by which a rock's Structure is changed by pressure, heat, and moisture. p133

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Change in shape due to heat from friction, stress and pressure. p134

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epetitive layering in metamorphic rocks

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Hot, molten rock p 118

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Occurs when hot magma moves into rock, heating and changing it.
p 134

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Metamorphism that's due only to the consequences of very deep burial.

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The breakup of rock due to exposure to processes that occur at Earth's surface. p 258

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An occurrence of rock or sediment that contains sufficient minerals with economically important elements, typically metals, that can be economically extracted from the deposit.

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Processes involving interactions between hot water or steam and rocks and minerals. Process in which ore forms as a result of interactions between hot water or steam, dissolved metals, and rocks and minerals.

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KIT - IKFT - Thermochemical Conversion of Biomass - Platform Chemicals and Materials from Biomass - Hydrothermal Processes

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A process in water at raised temperatures and pressures is called a hydrothermal process. The concept comes originally from the geology. The picture on the left shows a simplified overview about different hydrothermal processes and includes the vapour pressure curve of the water.

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A surface mineral deposit formed by the mechanical concentration of mineral particles (usually by water) from weathered debris.

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A chemically precipitated sedimentary rock that formed when dissolved ions were concentrated by evaporation of water.

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A gray, yellow, or reddish brown rock composed of a mix of aluminum oxides and hydroxides. It is the principal ore of aluminum.

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The known supply of ore in the ground.

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Fuels formed from the partially decayed remains of plants and animals. Most common examples are petroleum, coal, and natural gas.

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Coal is an organic sedimentary rock that forms from the accumulation and preservation of plant materials, usually in a swamp environment.

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A natural occurring liquid composed of a complex mixture of hydrocarbons.

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Porous and permeable Rock in which liquid petroleum or gas accumulate.

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A mixture of naturally occurring light hydrocarbons composed mainly of methane.

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Sand deposits permeated with heavy oil and an oil-like substance called bitumen.
Tar sands are dug up and heated with steam to make bitumen fluid, which is separated out from the sand. The bitumen is then treated chemically and heated to convert it to crude oil.

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A dry desert lake bed

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A large elevated area of comparatively flat land.

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A flat-topped mountain, with several steep cliff faces. A butte is smaller and more tower-like than a mesa.

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Wind-deposited sediment consisting of fine, silt-sized particles.

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"Loess" is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. It covers about 10% of the Earth's surface. Loess is an aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20-50 micrometer size range, twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate.

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Weathering is the breakdown of rocks at the Earth’s surface, by the action of rainwater, extremes of temperature, and biological activity.

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Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind or water. A similar process, weathering, breaks down or dissolves rock, but does not involve movement.

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Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind or water. A similar process, weathering, breaks down or dissolves rock, but does not involve movement. Erosion is the opposite of deposition, the geological process in which earthen materials are deposited, or built up, on a landform. Most erosion is performed by liquid water, wind, or ice (usually in the form of a glacier). If the wind is dusty, or water or glacial ice is muddy, erosion is taking place. The brown color indicates that bits of rock and soil are suspended in the fluid (air or water) and being transported from one place to another. This transported material is called sediment.

Physical erosion describes the process of rocks changing their physical properties without changing their basic chemical composition. Physical erosion often causes rocks to get smaller or smoother. Rocks eroded through physical erosion often form clastic sediments. Clastic sediments are composed of fragments of older rocks that have been transported from their place of origin. Landslides and other forms of mass wasting are associated with physical weathering. These processes cause rocks to dislodge from hillsides and crumble as they tumble down a slope.

Plant growth can also contribute to physical erosion in a process called bioerosion. Plants break up earthen materials as they take root, and can create cracks and crevices in rocks they encounter. Ice and liquid water can also contribute to physical erosion as their movement forces rocks to crash together or crack apart. Some rocks shatter and crumble, while others are worn away. River rocks are often much smoother than rocks found elsewhere, for instance, because they have been eroded by constant contact with other river rocks.

Erosion by Water

Liquid water is the major agent of erosion on Earth. Rain, rivers, floods, lakes, and the ocean carry away bits of soil and sand and slowly wash away the sediment. Rainfall produces four types of soil erosion: splash erosion, sheet erosion, rill erosion, and gully erosion.

Splash erosion describes the impact of a falling raindrop, which can scatter tiny soil particles as far as 0.6 meters (two feet).

Sheet erosion describes erosion caused by runoff.

Rill erosion describes erosion that takes place as runoff develops into discrete streams (rills).

Finally, gully erosion is the stage in which soil particles are transported through large channels.

The Fish River Canyon, in southern Namibia, is the largest canyon in Africa and a product of valley erosion. Over millions of years, the Fish River wore away at the hard gneiss bedrock, carving a canyon about 160 kilometers (99 miles) in length, 27 kilometers (17 miles) wide, and 550 meters (1,084 feet) deep.

The battering force of ocean waves also erodes seaside cliffs. The action of erosion can create an array of coastal landscape features. For example, erosion can bore holes that form caves. When water breaks through the back of the cave, it can create an arch. The continual pounding of waves can cause the top of the arch to fall, leaving nothing but rock columns called sea stacks. The seven remaining sea stacks of Twelve Apostles Marine National Park, in Victoria, Australia, are among the most dramatic and well-known of these features of coastal erosion.

Erosion by Wind

Erosion by Ice

Ice, usually in the form of glaciers, can erode the earth and create dramatic landforms. In frigid areas and on some mountaintops, glaciers move slowly downhill and across the land. As they move, they transport everything in their path, from tiny grains of sand to huge boulders. Rocks carried by glaciers scrape against the ground below, eroding both the ground and the rocks. In this way, glaciers grind up rocks and scrape away the soil. Moving glaciers gouge out basins and form steep-sided mountain valleys. Eroded sediment called moraine is often visible on and around glaciers.

Several times in Earth's history, vast glaciers covered parts of the Northern Hemisphere. These glacial periods are known as ice ages. Ice Age glaciers carved much of the modern northern North American and European landscape. Ice Age glaciers scoured the ground to form what are now the Finger Lakes in the U.S. state of New York, for example. They carved fjords, deep inlets along the coast of Scandinavia. The snout of a glacier eroded Cape Cod Bay, Massachusetts, U.S., and formed the recognizable fishhook shape of Cape Cod itself.

Today, in places such as Greenland and Antarctica, glaciers continue to erode the earth. Ice sheets there can be more than a mile thick, making it difficult for scientists to measure the speed and patterns of erosion. However, ice sheets do erode remarkably quickly-as much as half a centimeter (0.2 inch) every year.

Other Forces of Erosion

Factors Impacting Erosion

Some of the natural factors impacting erosion in a landscape include climate, topography, vegetation, and tectonic activity. Climate is perhaps the most influential force impacting the effect of erosion on a landscape. Climate includes precipitation and wind. Climate also includes seasonal variability, which influences the likelihood of weathered sediments being transported during a weather event such as a snowmelt, breeze, or hurricane. Topography, the shape of surface features of an area, can contribute to how erosion impacts that area. The earthen floodplains of river valleys are much more prone to erosion than rocky flood channels, which may take centuries to erode. Soft rock like chalk will erode more quickly than hard rocks like granite.

Vegetation can slow the impact of erosion. Plant roots adhere to soil and rock particles, preventing their transport during rainfall or wind events. Trees, shrubs, and other plants can even limit the impact of mass wasting events such as landslides and other natural hazards such as hurricanes. Deserts, which generally lack thick vegetation, are often the most eroded landscapes on the planet.

Finally, tectonic activity shapes the landscape itself, and thus influences the way erosion impacts an area. Tectonic uplift, for example, causes one part of the landscape to rise higher than others. In a span of about 5 million years, tectonic uplift caused the Colorado River to cut deeper and deeper into the Colorado Plateau, land in what is now the U.S. state of Arizona. It eventually formed the Grand Canyon, which is more than 1,600 meters (one mile) deep and as much as 29 kilometers (18 miles) wide in some places.

Erosion and People
Deposition, Soils, and Sediments
Eroded sediments have profoundly influenced the development of civilizations around the world. Agricultural development is often reliant on the nutrient-rich soils created by the accumulation of eroded earth. When the velocity of wind or water slows, eroded sediment is deposited in a new location. The sediment builds up in a process called sedimentation and creates fertile land. River deltas are made almost entirely of sediment that has eroded from the banks and bed of a river.

The rich delta soils of the San Joaquin and Sacramento rivers in northern California, for example, have created one of the most agriculturally productive areas in the world. Loess is an agriculturally rich sediment made almost entirely of wind-blown, eroded sediment.

The Yellow River in central China gets its name from the yellow loess blown into and suspended in its water. The fertile lands around the Yellow River have been among China's most productive for thousands of years.

Erosion is a natural process, but human activity can make it happen more quickly. Human activity altering the vegetation of an area is perhaps the biggest human factor contributing to erosion. Trees and plants hold soil in place. When people cut down forests or plow up grasses for agriculture and development, the soil is more vulnerable to washing or blowing away. Landslides become more common. Water rushes over exposed soil rather than soaking into it, causing flooding.

The rise in temperature is also quickly melting glaciers. The slower, more massive form of glacial erosion is being supplanted by the cumulative impact of rill, gully, and valley erosion. In areas downstream from glacial snouts, rapidly melting glaciers are contributing to sea level rise. The rising sea erodes beaches more quickly.

Erosion control is the process of reducing erosion by wind and water. Farmers and engineers must regularly practice erosion control. Sometimes, engineers simply install structures to physically prevent soil from being transported. Gabions are huge wireframes that hold boulders in place, for instance. Gabions are often placed near cliffs. These cliffs, often near the coast, have homes, businesses, and highways near them. When erosion by water or wind threatens to tumble the boulders toward buildings and cars, gabions protect landowners and drivers by holding the rocks in place.

Living shorelines are another form of erosion control in wetland areas. Living shorelines are constructed by placing native plants, stone, sand, and even living organisms such as oysters along wetland coasts. These plants help anchor the soil to the area, preventing erosion. By securing the land, living shorelines establish a natural habitat. They protect coastlines from powerful storm surges as well as erosion.

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Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind or water.

# data[].attributes.attachment_link.readable_text
Chemical weathering is caused by rain water reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts. These reactions occur particularly when the water is slightly acidic.

Where does it occur?

These chemical processes need water, and occur more rapidly at higher temperature, so warm, damp climates are best. Chemical weathering (especially hydrolysis and oxidation) is the first stage in the production of soils.

How does it occur?

There are different types of chemical weathering, the most important are:

Solution - removal of rock in solution by acidic rainwater. In particular, limestone is weathered by rainwater containing dissolved CO2, (this process is sometimes called carbonation).

Hydrolysis - the breakdown of rock by acidic water to produce clay and soluble salts.

Oxidation - the breakdown of rock by oxygen and water, often giving iron-rich rocks a rusty-coloured weathered surface.

# data[].attributes.attachment_link.description
Chemical weathering is caused by rain water reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts. These reactions occur particularly when the water is slightly acidic. Where does it occur? These chemical processes need water, and occur more rapidly at higher temperature, so warm, damp climates are best.

# data[].attributes.attachment_link.readable_text
Chemical weathering is caused by rain water reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts. These reactions occur particularly when the water is slightly acidic.

Where does it occur?

These chemical processes need water, and occur more rapidly at higher temperature, so warm, damp climates are best. Chemical weathering (especially hydrolysis and oxidation) is the first stage in the production of soils.

How does it occur?

There are different types of chemical weathering, the most important are:

Solution - removal of rock in solution by acidic rainwater. In particular, limestone is weathered by rainwater containing dissolved CO2, (this process is sometimes called carbonation).

Hydrolysis - the breakdown of rock by acidic water to produce clay and soluble salts.

Oxidation - the breakdown of rock by oxygen and water, often giving iron-rich rocks a rusty-coloured weathered surface.

# data[].attributes.attachment_link.description
Chemical weathering is caused by rain water reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts. These reactions occur particularly when the water is slightly acidic. Where does it occur? These chemical processes need water, and occur more rapidly at higher temperature, so warm, damp climates are best.

# data[].attributes.attachment_link.readable_text
The supercontinent Pangaea in the early Mesozoic (at 200 Ma)

Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million years ago, and began to break apart about 200 million years ago, at the end of the Triassic and beginning of the Jurassic. In contrast to the present Earth and its distribution of continental mass, Pangaea was C-shaped, with the bulk of its mass stretching between Earth's northern and southern polar regions and surrounded by the superocean Panthalassa and the Paleo-Tethys and subsequent Tethys Oceans. Pangaea is the most recent supercontinent to have existed and the first to be reconstructed by geologists.

Origin of the concept

Alfred Wegener c. 1924-1930

World map of Pangaea created by Alfred Wegener to illustrate his concept

The name "Pangaea" is derived from Ancient Greek pan (, "all, entire, whole") and or Gaea (, " Mother Earth, land"). The first to suggest that the continents were once joined and later separated may have been Abraham Ortelius in 1596. The concept that the continents once formed a contiguous land mass was hypothesised, with corroborating evidence, by Alfred Wegener, the originator of the scientific theory of continental drift, in three 1912 academic journal articles written in German titled Die Entstehung der Kontinente ( The Origin of Continents). He expanded upon his hypothesis in his 1915 book of the same title, in which he postulated that, before breaking up and drifting to their present locations, all the continents had formed a single supercontinent that he called the Urkontinent.

Wegener used the name "Pangaea" once in the 1920 edition of his book, referring to the ancient supercontinent as "the Pangaea of the Carboniferous". He used the Germanized form Pangäa, but the name entered German and English scientific literature (in 1922 and 1926, respectively) in the Latinized form Pangaea, especially during a symposium of the American Association of Petroleum Geologists in November 1926.

Wegener originally proposed that the breakup of Pangaea was caused by centripetal forces from Earth's rotation acting on the high continents. However, this mechanism was easily shown to be physically implausible, which delayed acceptance of the Pangaea hypothesis. Arthur Holmes proposed the more plausible mechanism of mantle convection, which, together with evidence provided by the mapping of the ocean floor following the Second World War, led to the development and acceptance of the theory of plate tectonics. This theory provides the widely-accepted explanation for the existence and breakup of Pangaea.

Evidence of existence

The distribution of fossils across the continents is one line of evidence pointing to the existence of Pangaea.

The geography of the continents bordering the Atlantic Ocean was the first evidence suggesting the existence of Pangaea. The seemingly close fit of the coastlines of North and South America with Europe and Africa was remarked on almost as soon as these coasts were charted. Careful reconstructions showed that the mismatch at the 500 fathoms (3,000 feet; 910 meters) contour was less than 130 km (81 mi), and it was argued that this was much too similar to be attributed to coincidence.

Additional evidence for Pangaea is found in the geology of adjacent continents, including matching geological trends between the eastern coast of South America and the western coast of Africa. The polar ice cap of the Carboniferous covered the southern end of Pangaea. Glacial deposits, specifically till, of the same age and structure are found on many separate continents that would have been together in the continent of Pangaea. The continuity of mountain chains provides further evidence, such as the Appalachian Mountains chain extending from the southeastern United States to the Scandinavian Caledonides of Europe; these are now believed to have formed a single chain, the Central Pangean Mountains.

Fossil evidence for Pangaea includes the presence of similar and identical species on continents that are now great distances apart. For example, fossils of the therapsid Lystrosaurus have been found in South Africa, India and Antarctica, alongside members of the Glossopteris flora, whose distribution would have ranged from the polar circle to the equator if the continents had been in their present position; similarly, the freshwater reptile Mesosaurus has been found in only localized regions of the coasts of Brazil and West Africa.

Geologists can also determine the movement of continental plates by examining the orientation of magnetic minerals in rocks. When rocks are formed, they take on the magnetic orientation of the Earth, showing which direction the poles lie relative to the rock; this determines latitudes and orientations (though not longitudes). Magnetic differences between samples of sedimentary and intrusive igneous rock whose age varies by millions of years is due to a combination of magnetic polar wander (with a cycle of a few thousand years) and the drifting of continents over millions of years. The polar wander component, which is identical for all contemporaneous samples, can be subtracted, leaving the portion that shows continental drift and can be used to help reconstruct earlier continental latitudes and orientations.

Appalachian orogeny

Pangaea is the most recent supercontinent reconstructed from the geologic record and therefore is by far the best understood. The formation of supercontinents and their breakup appears to be cyclical through Earth's history. There may have been several others before Pangaea.

Paleomagnetic measurements help geologists determine the latitude and orientation of ancient continental blocks, and newer techniques may help determine longitudes. Paleontology helps determine ancient climates, confirming latitude estimates from paleomagnetic measurements, and the distribution of ancient forms of life provides clues on which continental blocks were close to each other at particular geological moments. However, reconstructions of continents prior to Pangaea, including the ones in this section, remain partially speculative, and different reconstructions will differ in some details.

Previous supercontinents

The fourth-last supercontinent, called Columbia or Nuna, appears to have assembled in the period 2.0-1.8 billion years ago (Ga). Columbia/Nuna broke up, and the next supercontinent, Rodinia, formed from the accretion and assembly of its fragments. Rodinia lasted from about 1.3 billion years ago until about 750 million years ago, but its configuration and geodynamic history are not nearly as well understood as those of the later supercontinents, Pannotia and Pangaea.

According to one reconstruction, when Rodinia broke up, it split into three pieces: proto- Laurasia, proto-Gondwana, and the smaller Congo Craton. Proto-Laurasia and proto-Gondwana were separated by the Proto-Tethys Ocean. Proto-Laurasia split apart to form the continents of Laurentia, Siberia, and Baltica. Baltica moved to the east of Laurentia, and Siberia moved northeast of Laurentia. The split created two oceans, the Iapetus Ocean and Paleoasian Ocean.

Most of these landmasses coalesced again to form the relatively short-lived supercontinent Pannotia, which included large areas of land near the poles and a small strip connecting the polar masses near the equator. Pannotia lasted until 540 Ma, near the beginning of the Cambrian and then broke up, giving rise to the continents of Laurentia, Baltica, and the southern supercontinent Gondwana.

Formation of Euramerica (Laurussia)

In the Cambrian, Laurentia-which would later become North America-sat on the equator with three bordering oceans: the Panthalassic Ocean to the north and west, the Iapetus Ocean to the south, and the Khanty Ocean to the east. In the early Ordovician, around 480 Ma, the microcontinent Avalonia-a landmass incorporating fragments of what would become eastern Newfoundland, the southern British Isles, and parts of Belgium, northern France, Nova Scotia, New England, South Iberia, and northwest Africa-broke free from Gondwana and began its journey to Laurentia. Baltica, Laurentia, and Avalonia all came together by the end of the Ordovician to form a landmass called Euramerica or Laurussia, closing the Iapetus Ocean. The collision resulted in the formation of the northern Appalachians. Siberia sat near Euramerica, with the Khanty Ocean between the two continents. While all this was happening, Gondwana drifted slowly towards the South Pole. This was the first step of the formation of Pangaea.

Collision of Gondwana with Euramerica

The second step in the formation of Pangaea was the collision of Gondwana with Euramerica. By the middle of the Silurian, 430 Ma, Baltica had already collided with Laurentia, forming Euramerica, an event called the Caledonian orogeny. As Avalonia inched towards Laurentia, the seaway between them, a remnant of the Iapetus Ocean, was slowly shrinking. Meanwhile, southern Europe broke off from Gondwana and began to move towards Euramerica across the Rheic Ocean. It collided with southern Baltica in the Devonian.

By the late Silurian, Annamia ( Indochina) and the South China Craton split from Gondwana and moved northward, shrinking the Proto-Tethys Ocean and opening the Paleo-Tethys Ocean to the south. In the Devonian Gondwana moved towards Euramerica, causing the Rheic Ocean to shrink. In the Early Carboniferous, northwest Africa had touched the southeastern coast of Euramerica, creating the southern portion of the Appalachian Mountains, the Meseta Mountains, and the Mauritanide Mountains, an event called the Variscan orogeny. South America moved northward to southern Euramerica, while the eastern portion of Gondwana ( India, Antarctica, and Australia) headed toward the South Pole from the equator. North and South China were on independent continents. The Kazakhstania microcontinent had collided with Siberia. (Siberia had been a separate continent for millions of years since the breakup of Pannotia.)

The Variscan orogeny raised the Central Pangaean Mountains, which were comparable to the modern Himalayas in scale. With Pangaea stretching from the South Pole across the equator and well into the Northern Hemisphere, an intense megamonsoon climate was established, except for a perpetually wet zone immediately around the central mountains.

Formation of Laurasia

Western Kazakhstania collided with Baltica in the late Carboniferous, closing the Ural Ocean and the western Proto-Tethys ( Uralian orogeny), causing the formation of the Ural Mountains and Laurasia. This was the last step of the formation of Pangaea. Meanwhile, South America had collided with southern Laurentia, closing the Rheic Ocean and completing the Variscian orogeny with the formation the southernmost part of the Appalachians and Ouachita Mountains. By this time, Gondwana was positioned near the South Pole, and glaciers formed in Antarctica, India, Australia, southern Africa, and South America. The North China Craton collided with Siberia by the Jurassic, completely closing the Proto-Tethys Ocean.

By the Early Permian, the Cimmerian plate split from Gondwana and moved towards Laurasia, thus closing the Paleo-Tethys Ocean and forming the Tethys Ocean in its southern end. Most of the landmasses were all in one. By the Triassic, Pangaea rotated a little, and the Cimmerian plate was still travelling across the shrinking Paleo-Tethys until the Middle Jurassic. By the Late Triassic, the Paleo-Tethys had closed from west to east, creating the Cimmerian Orogeny. Pangaea, which looked like a C, with the Tethys Ocean inside the C, had rifted by the Middle Jurassic.

Paleogeography of Earth in the late Cambrian, around 490 Ma

Paleogeography of Earth in the middle Silurian, around 430 Ma. Avalonia and Baltica have fused with Laurentia to form Laurussia.

Paleogeography of Earth in the late Carboniferous, around 310 Ma. Laurussia has fused with Gondwana to form Pangaea.

Paleogeography of the Earth at the Permian-Triassic boundary, around 250 Ma. Siberia has fused with Pangaea to complete the assembly of the supercontinent.

Dicroidium zuberi, an Early Triassic plant from Pangaea (present-day Argentina)

The four floristic provinces of the world at the Permian-Carboniferous boundary, 300 million years ago

Pangaea existed as a supercontinent for 160 million years, from its assembly around 335 Ma (Early Carboniferous) to its breakup 175 Ma (Middle Jurassic). During this interval, important developments in the evolution of life took place. The seas of the Early Carboniferous were dominated by rugose corals, brachiopods, bryozoans, sharks, and the first bony fish. Life on land was dominated by lycopsid forests inhabited by insects and other arthropods and the first tetrapods. By the time Pangaea broke up, in the Middle Jurassic, the seas swarmed with molluscs (particularly ammonites), ichthyosaurs, sharks and rays, and the first ray-finned bony fishes, while life on land was dominated by forests of cycads and conifers in which dinosaurs flourished and in which the first true mammals had appeared.

The evolution of life in this time reflected the conditions created by the assembly of Pangaea. The union of most of the continental crust into one landmass reduced the extent of sea coasts. Increased erosion from uplifted continental crust increased the importance of floodplain and delta environments relative to shallow marine environments. Continental assembly and uplift also meant increasingly arid land climates, favoring the evolution of amniote animals and seed plants, whose eggs and seeds were better adapted to dry climates. The early drying trend was most pronounced in western Pangaea, which became a center of the evolution and geographical spread of amniotes.

Coal swamps typically form in perpetually wet regions close to the equator. The assembly of Pangaea disrupted the intertropical convergence zone and created an extreme monsoon climate that reduced the deposition of coal to its lowest level in the last 300 million years. During the Permian, coal deposition was largely restricted to the North and South China microcontinents, which were among the few areas of continental crust that had not joined with Pangaea. The extremes of climate in the interior of Pangaea are reflected in bone growth patterns of pareiasaurs and the growth patterns in gymnosperm forests.

Early Triassic Lystrosaurus fossil from South Africa

The lack of oceanic barriers is thought to have favored cosmopolitanism, in which successful species attain wide geographical distribution. Cosmopolitanism was also driven by mass extinctions, including the Permian-Triassic extinction event, the most severe in the fossil record, and also the Triassic-Jurassic extinction event. These events resulted in disaster fauna showing little diversity and high cosmopolitanism, including Lystrosaurus, which opportunistically spread to every corner of Pangaea following the Permian-Triassic extinction event. On the other hand, there is evidence that many Pangaean species were provincial, with a limited geographical range, despite the absence of geographical barriers. This may be due to the strong variations in climate by latitude and season produced by the extreme monsoon climate. For example, cold-adapted pteridosperms (early seed plants) of Gondwana were blocked from spreading throughout Pangaea by the equatorial climate, and northern pteridosperms ended up dominating Gondwana in the Triassic.

Mass extinctions

The tectonics and geography of Pangaea may have worsened the Permian-Triassic extinction event or other mass extinctions. For example, the reduced area of continental shelf environments may have left marine species vulnerable to extinction. However, no evidence for a species-area effect has been found in more recent and better characterized portions of the geologic record. Another possibility is that reduced seafloor spreading associated with the formation of Pangaea, and the resulting cooling and subsidence of oceanic crust, may have reduced the number of islands that could have served as refugia for marine species. Species diversity may have already been reduced prior to mass extinction events due to mingling of species possible when formerly separate continents were merged. However, there is strong evidence that climate barriers continued to separate ecological communities in different parts of Pangaea. The eruptions of the Emeishan Traps may have eliminated South China, one of the few continental areas not merged with Pangaea, as a refugium.

Rifting and break-up

The breakup of Pangaea over time

There were three major phases in the break-up of Pangaea.

Opening of the Atlantic

The Atlantic Ocean did not open uniformly; rifting began in the north-central Atlantic. The first breakup of Pangaea is proposed for the late Ladinian (230 Ma) with initial spreading in the opening central Atlantic. Then the rifting proceeded along the eastern margin of North America, the northwest African margin and the High, Saharan and Tunisian Atlas Mountains.

Another phase began in the Early-Middle Jurassic (about 175 Ma), when Pangaea began to rift from the Tethys Ocean in the east to the Pacific Ocean in the west. The rifting that took place between North America and Africa produced multiple failed rifts. One rift resulted in the North Atlantic Ocean.

The South Atlantic did not open until the Cretaceous when Laurasia started to rotate clockwise and moved northward with North America to the north, and Eurasia to the south. The clockwise motion of Laurasia led much later to the closing of the Tethys Ocean and the widening of the "Sinus Borealis", which later became the Arctic Ocean. Meanwhile, on the other side of Africa and along the adjacent margins of east Africa, Antarctica and Madagascar, rifts formed that led to the formation of the southwestern Indian Ocean in the Cretaceous.

Break-up of Gondwana

The second major phase in the break-up of Pangaea began in the Early Cretaceous (150-140 Ma), when Gondwana separated into multiple continents (Africa, South America, India, Antarctica, and Australia). The subduction at Tethyan Trench probably caused Africa, India and Australia to move northward, causing the opening of a "South Indian Ocean". In the Early Cretaceous, Atlantica, today's South America and Africa, separated from eastern Gondwana. Then in the Middle Cretaceous, Gondwana fragmented to open up the South Atlantic Ocean as South America started to move westward away from Africa. The South Atlantic did not develop uniformly; rather, it rifted from south to north.

Also, at the same time, Madagascar and Insular India began to separate from Antarctica and moved northward, opening up the Indian Ocean. Madagascar and India separated from each other 100-90 Ma in the Late Cretaceous. India continued to move northward toward Eurasia at 15 centimeters (6 in) per year (a plate tectonic record), closing the eastern Tethys Ocean, while Madagascar stopped and became locked to the African Plate. New Zealand, New Caledonia and the rest of Zealandia began to separate from Australia, moving eastward toward the Pacific and opening the Coral Sea and Tasman Sea.

Opening of the Norwegian Sea and break-up of Australia and Antarctica

The third major and final phase of the break-up of Pangaea occurred in the early Cenozoic ( Paleocene to Oligocene). Laurasia split when Laurentia broke from Eurasia, opening the Norwegian Sea about 60-55 Ma. The Atlantic and Indian Oceans continued to expand, closing the Tethys Ocean.

Meanwhile, Australia split from Antarctica and moved quickly northward, just as India had done more than 40 million years before. Australia is currently on a collision course with eastern Asia. Both Australia and India are currently moving northeast at 5-6 centimeters (2-3 in) per year. Antarctica has been near or at the South Pole since the formation of Pangaea about 280 Ma. India started to collide with Asia beginning about 35 Ma, forming the Himalayan orogeny and closing the Tethys Ocean; this collision continues today. The African Plate started to change directions, from west to northwest toward Europe, and South America began to move in a northward direction, separating it from Antarctica and allowing complete oceanic circulation around Antarctica for the first time. This motion, together with decreasing atmospheric carbon dioxide concentrations, caused a rapid cooling of Antarctica and allowed glaciers to form. This glaciation eventually coalesced into the kilometers-thick ice sheets seen today. Other major events took place during the Cenozoic, including the opening of the Gulf of California, the uplift of the Alps, and the opening of the Sea of Japan. The break-up of Pangaea continues today in the Red Sea Rift and East African Rift.

Climate change after Pangaea

The breakup of Pangaea was accompanied by outgassing of large quantities of carbon dioxide from continental rifts. This produced a Mesozoic CO ₂ high that contributed to the very warm climate of the Early Cretaceous. The opening of the Tethys Ocean also contributed to the warming of the climate. The very active mid-ocean ridges associated with the breakup of Pangaea raised sea levels to the highest in the geological record, flooding much of the continents.

The expansion of the temperate climate zones that accompanied the breakup of Pangaea may have contributed to the diversification of the angiosperms.

References

1. As "Pangaea", it appears in ^ Greek mythology as a mountain battle site during the Titanomachia. As "Pangaeus", it was the name of a specific mountain range in southern Thrace. "Pangaea" also appears in Vergil's Georgics and Lucan's Pharsalia The scholiast on Lucan glossed Pangaea id est totum terra-"Pangaea: that is, all land"-as having received its name on account of its smooth terrain and unexpected fertility.

2. See: ^

Wegener, Alfred, Die Entstehung der Kontinente und Ozeane, 2nd ed. (Braunschweig, Germany: F. Vieweg, 1920), p. 120: "Schon die Pangäa der Karbonzeit hatte so einen Vorderrand ... " [Already the Pangaea of the Carboniferous era had such a leading edge ...] (In the 1922 edition, see p. 130.)

Wegener, A.; Krause, R.; Thiede, J. (2005). "Kontinental-Verschiebungen: Originalnotizen und Literaturauszüge"(Continental drift: the original notes and quotations). Berichte zur Polar- und Meeresforschung (Reports on Polar and Marine Research) 516. Alfred-Wegener-Institut: Bremerhaven, p. 4, n. 2

3. ^ Jaworski, Erich (1922). "Die A. Wegenersche Hypothese der Kontinentalverschiebung". Geologische Rundschau. 13 (3): 273-296. Bibcode:1922GeoRu..13..273J. doi:10.1007/bf01799790. S2CID 131160418.

4. Murck, Barbara W. and Skinner, Brian J. (1999) ^ Geology Today: Understanding Our Planet, Study Guide, Wiley, ISBN 978-0-471-32323-5

5. ^ Merali, Zeeya and Skinner, Brian J. (2009) Visualizing Earth Science, Wiley, ISBN 047174705X

6. ^ Pyron, R. Alexander (1 September 2014). "Biogeographic Analysis Reveals Ancient Continental Vicariance and Recent Oceanic Dispersal in Amphibians". Systematic Biology. 63 (5): 779-797. doi:10.1093/sysbio/syu042. PMID 24951557.

7. ^ Zhao, Guochun; Sun, M.; Wilde, Simon A.; Li, S.Z. (2004). "A Paleo-Mesoproterozoic supercontinent: assembly, growth and breakup". Earth-Science Reviews. 67 (1-2): 91-123. Bibcode:2004ESRv...67...91Z. doi:10.1016/j.earscirev.2004.02.003.

8. ^ Cocks, L. Robin M.; Torsvik, Trond H. (2013). "The dynamic evolution of the Palaeozoic geography of eastern Asia". Earth-Science Reviews. 117: 40-79. doi:10.1016/j.earscirev.2012.12.001.

9. ^ Otto-Bliesner, Bette L. (15 September 1993). "Tropical mountains and coal formation: A climate model study of the Westphalian (306 MA)". Geophysical Research Letters. 20 (18): 1947-1950. Bibcode:1993GeoRL..20.1947O. doi:10.1029/93GL02235.

10. ^ "Life of the Carboniferous". UC Museum of Paleontology. UC Berkeley.

11. ^ Ziegler, Alfred; Eshel, Gidon; Rees, P. McALLISTER; Rothfus, Thomas; Rowley, David; Sunderlin, David (September 2003). "Tracing the tropics across land and sea: Permian to present". Lethaia. 36 (3): 227-254. doi:10.1080/00241160310004657.

12. ^ Looy, Cindy V.; Ranks, Stephanie L.; Chaney, Dan S.; Sanchez, Sophie; Steyer, Jean-Sébastien; Smith, Roger M.H.; Sidor, Christian A.; Myers, Timothy S.; Ide, Oumarou; Tabor, Neil J. (June 2016). "Biological and physical evidence for extreme seasonality in central Permian Pangea". Palaeogeography, Palaeoclimatology, Palaeoecology. 451: 210-226. Bibcode:2016PPP...451..210L. doi:10.1016/j.palaeo.2016.02.016.

13. ^ Sahney, Sarda; Benton, Michael J (7 April 2008). "Recovery from the most profound mass extinction of all time". Proceedings of the Royal Society B: Biological Sciences. 275 (1636): 759-765. doi:10.1098/rspb.2007.1370. PMC . PMID 18198148.

14. ^ Button, David J.; Lloyd, Graeme T.; Ezcurra, Martín D.; Butler, Richard J. (December 2017). "Mass extinctions drove increased global faunal cosmopolitanism on the supercontinent Pangaea". Nature Communications. 8 (1): 733. Bibcode:2017NatCo...8..733B. doi:10.1038/s41467-017-00827-7. PMC . PMID 29018290.

15. Antonio Schettino, Eugenio Turco: ^ Breakup of Pangaea and plate kinematics of the central Atlantic and Atlas regions. In: Geophysical Journal International, Band 178, Ausgabe 2, August 2009, S. 1078-1097.

16. ^ Deconto, Robert M.; Pollard, David (2003). "Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric CO₂" (PDF). Nature. 421 (6920): 245-9. Bibcode:2003Natur.421..245D. doi:10.1038/nature01290. PMID 12529638. S2CID 4326971.

17. ^ Chaboureau, Anne-Claire; Sepulchre, Pierre; Donnadieu, Yannick; Franc, Alain (30 September 2014). "Tectonic-driven climate change and the diversification of angiosperms". Proceedings of the National Academy of Sciences. 111 (39): 14066-14070. Bibcode:2014PNAS..11114066C. doi:10.1073/pnas.1324002111. PMC . PMID 25225405.

External links

# data[].attributes.attachment_link.description
Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million years ago, and began to break apart about 200 million years ago, at the end of the Triassic and beginning of the Jurassic.

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The rigid outer part of the earth, consisting of the crust and upper mantle.

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The upper layer of the earth’s mantle. Below the lithosphere. Extends about 100km (60 miles) to about 700km (450 miles) below the Earth’s surface.

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The formation of new areas of oceanic crust. Occurs through the upwelling of magma at mid ocean ridges and it’s subsequent outward movement on either side.

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Locations were tectonic plates are moving away from one another.

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Locations where tectonic plates are moving towards each other.

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Area where two tectonic plates slide past each other

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Subduction is a geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced to sink due to gravity into the mantle.[

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The shaking of Earth's crust caused by a release of energy.

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Body waves that squeeze and stretch rock materials as they pass through Earth. Also known as compressional waves or primary waves

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Body waves that cause particles of rock material to move at right angles to the direction in which the waves are traveling. Also known as shear waves or secondary waves

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Earthquake waves that travel along Earth's surface: Love waves and Rayleigh waves are two types of surface waves.

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An instrument that detects and records waves produced by earthquakes.

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A temporary state in which loose soil and rock materials take on the property of liquid, often the result of severe ground shaking.

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The point on Earth's surface directly above the focus of an earthquake.

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The scientific study of the ocean using chemistry, biology,physics,geology and other sciences.

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A technique that involves the use of a special hollow drill to remove cylindrical samples from sediment or rock, so they can be analyzed for certain properties or features.

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The flat or gently sloping submerged part of the continent: extends from the shoreline out to the continental slope.

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The steep boundary between the continental shelf and the continental rise.

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A large flat area on the ocean floor, composed of sediments that originated mostly on continents.

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A comparison of the actual amount of water vapor in the air with the maximum amount of water vapor that can be present in the air at a given temperature and pressure.

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Dew Point (temperature at which precipitation occurs)

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Dew Point (temperature at which precipitation occurs)

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The temperature at which saturation occurs and condensation begins; a measure of the amount of water vapor in the air.

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Microscopic particle on which water vapor condenses to form cloud droplets.

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Clouds that form in low, horizontal layers

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Thick fluffy clouds with flat bases, formed by vertically rising air currents.

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High-altitude clouds that are thin, feathery tufts of ice crystals

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The percent of a material's volume that is pore space.

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the capacity of a rock to transmit a fluid

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A well that is dug or drilled down to the water table.

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An arrangement of a permeable layer or rock sandwiched between two layers of impermeable rock.