Permian and Cretaceous Mass Extinctions Essay

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Assess the different hypotheses put forward for the mass extinctions at the end of the Permian and Cretaceous (KT) Periods. A mass extinction is an event in which at least 25-75% of species in the global environment are eradicated in a short period of time. Where as a regional extinction event is when the extinction is confined to a specific zone. Five mass extinctions have occurred throughout time, two of the most well known of these are the Permian and Cretaceous extinction events. There are several hypotheses that are used to explain the causes of mass extinctions. Climate change, the warming or cooling of global environments over a short period of time, can lead to other occurrences. Shifts in climate can cause extinction by…show more content…
A crater, the Bedout crater, in Australia has been discovered. A bolide impact would have lead to mass death of marine and terrestrial organisms. The force of the impact could have released methane from stored organic matter and large earthquakes. These earthquakes would have triggered the volcanism in the Siberian traps, leading to the release of large amounts of CO2 and sulfur dioxide. These gases combined with methane previously released would have created a noxious atmosphere, combined with climate change that killed a large scale of life. It is most likely that a simultaneous occurrence of the different global environmental changes was responsible for ending the Permian period, and the lives of 96% of species. Each environmental issue is a major geological event, and amplified the other events, leading to catastrophic environmental situation, in which barely any life could survive. The Cretaceous – Tertiary mass extinction, commonly referred to as the KT extinction, occurred 65 million years ago. As the most recant extinction event it is more easily studied as more evidence has been preserved than for the earlier extinctions. This extinction is the most commonly known, as it is the extinction of the dinosaurs, but the smallest scale mass extinction with only 76% of species dying out. Evidence for catastrophism at the KT boundary can be found in a layer of greenish

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