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Carbon Isotopes, measured from the preserved soils of the Ordovician Period, estimated that atmospheric carbon levels were 14-16 times higher. This led to the belief of high volcanic activity. Clear evidence of warm temperatures in the tropics can be seen in the extensive Ordovician limestone deposits with features similar to those found in modern tropical carbonate areas.
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85% of life was lost. Most life was aquatic life and locted within in the sea. These organisms included trilobites, brachiopods and graptolites.
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Scientisit have suggested that a drop in sea levels had caused the death of many of the species during this period. Its a well respected theory and has a good deal of evidence.
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Theories on the Devonian Period are conflicting so rocks in different areas and environments are used to help with what exactly happened during this period. This included on the distribution of evaporites, shelf carbonates, and corals. Breaking of the continents occurred during evidence and the evidence for this movement includes the reduction in ‘evaporitic environments in western Canada and the onset of humid and moist conditions in the area of New York’.
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70% - 80% of animal life was lost. These organisms included goniatites, tabulate corals, and brachiopods.
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This extinction is one of the greater mysteries of all the extinctions and the biggest supported theory for the cause of this extinction is global coolings, sort of like and ice age.
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Glacial levels were high during this time and the climate change to hot and dry in many areas, which is why it is believed that an increase in global temperatures led to this mass extinction. Many terrestrial plants and insects had evolved together and diversified during this period. This is the largest mass extinction to have occured and only about 10% of species survived.
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96% of all species had died during this extinction. This included crinoids, rugose corals, fusulinids
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This period's extinction is different from the previous one, in that the cause isn't within the Earth itself. Instead a popular theory suggests that an asteroid or comet had triggered volcanic activity.
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The Triassic Period was the start of great biodiversity in the Mesozoic Era. This period served as the start of the formation of the current continents and sea levels near the coasts rose at a gradual rate. This led to the formation of coral reefs near the coast and large marine reptiles. The first dinosaurs had also developed during this time period.
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22% of marine families and 52% of marine genera had died during this extinction. These organisms included Brachiopods, Gastropods, and Ammonoids.
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This period's cause of extinction is similar to that of the Permian one, where volcanic activity is to blame. But instead of a comet or asteroid causing it, it was the shifting of the tectonic plates causing the volcanic activity. This in turn increased atomospheric carbon to the point of intense global warming
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The Cretaceous period is the last period of the three periods that make up the Mesozoic Era. The Cretaceous Period is the longest of all the periods discussed in this project. During this period, Earth’s land was divided into two main continents, Laurasia and Gondwana. “Most of the present-day continents were separated from each other by expanses of water such as the North and South Atlantic Ocean”. India was later separate. Australia was connected to Antarctica.
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16%t of marine families, 47% of marine genera, and 18% of land vertebrate families died out during this extinction. These organisms included Tyrannosaurus, Velociraptor, and Sauropods. This was the end of dinosaurs.
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The theory of the Cretaceous extinction is a popular one, and the end of the dinosaurs. It was believed that a massive asteroid had caused the extinction of the dinosaurs. The asteroid was believed to be several miles wide
