Essay about Permian and Cretaceous Mass Extinctions

1418 Words Jul 11th, 2011 6 Pages
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
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This dark sediment contains high concentrations of Iridium, an element only found in the earth’s mantle, or on meteorites.

There are two main hypotheses that are used to explain the cause of the KT extinction and the end of the reign of the dinosaurs. The gradualist theory suggests that the KT extinction was caused by a regression of sea levels combined with global climate change caused by volcanism. There is evidence of a large deposit of Basalt located at the Deccan Plateau in India. The release of volcanic gases and ash would lead to climate change and the darkening of the sky. The volcanic ash released into the atmosphere at the time of the eruption, which then settled slowly all over the globe, could have caused the iridium layer mentioned above.

However, there is evidence that a bolide impact struck the earth in the Gulf of Mexico, the Chicxulub crater. The theory is known as the catastrophists theory. A bolide impact would explain the high levels of iridium and the shocked quartz, which has also been found throughout the globe in the same layer containing iridium. Shocked quartz is only formed under extremely high pressure, naturally formed in bolide impacts. The quartz contains fractures that show the impact shock.

The bolide impact would have cause mega tsunamis and wildfires throughout the world from the molten bits of meteorite raining down on the earth. Tektites have been found in sediments

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