Causes, Evidence, and Effects on Biodiversity
The most significant event of the Cretaceous era came at its end. Nearly 65 million years ago, the second most severe mass extinction in earth’s history occurred. This resulted in the loss of around 80% of species living at the time. Though nowhere near as severe as the end-Permian mass extinction, the end-Cretaceous extinction is the most well known mass extinction event. This is due to the violent event that caused it the extinction, as well as the chapter of earth’s history that it closed: the Dinosaurs. The Cretaceous Event ( often shortened to K-T event) Of the animals that were killed off were the flying reptiles (pterosaurs) and the last few mosasaurs and plesiosaurs, both early marine reptiles. Many mollusks and species of microscopic plankton were killed. Terrestrial plants suffered mass extinction as well. Almost 60% of terrestrial plants were lost. This led to high extinction rates among insect populations, especially insects that were highly specialized to feed on just a few types of plants had it the worst. It took approximately 9 million years for the global insect populations to recover from the Cretaceous extinction. Immediately after the extinction, the earth saw an explosion of short term species who respond well to fire, or other external disturbance. Evidence of the catastrophe comes from a thin rock layer deposited worldwide just after the impact. It is dominated by fossil plants whose descendants recover quickly after fires of other disturbances, such as Fire Weed in Alaska. The causes of the Cretaceous extinction are still being debated by paleontologists. Scientists agree that the main cause of the extinction was a...
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...asted about a million years. The eruption was not violent compared to others, but it was able to send ash as high as the stratosphere. So another theory is that shifting of the tectonic plates caused the Deccan Traps to erupt, causing the release of massive amounts of carbon dioxide out of the earths crust. This went on to create a global greenhouse effect that cooked the planet. This along with climate change from continental drift could have caused the K-T event. Paleontologist Richard Cowen believes the evidence of an asteroid impact is so strong that there is no point to explain that evidence as solely volcanic effects. We should concentrate on the fact that the K-T boundary coincided with two different, yet very dramatic events.
Cowen, Richard. A History of Life. 2nd ed. Vol. 1. Massachusetts: Cambridge, 1999. Print.
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