Describe the five major extinctions in the Phanerozoic and suggest possible causes for each.

The Phanerozoic’s Five Major Extinctions

Five major extinctions occurred in Earth’s history, the Phanerozoic Era. The Phanerozoic era started 541 million years back and continues today. These mass extinctions are the Ordovician, Devonian, Permian, Triassic, and Cretaceous. Many species of animals and plants disappeared from the planet during each event, with some never being recovered. Although there remains much to be debated about the causes, some theories can explain their existence. Ordovician was the first mass extinction in the Phanerozoic age, and it occurred approximately 444 million years back. The Ordovician is believed to have been the second largest mass extinction in Earth’s history, with up to 85 percent of species being extinct. It is believed that a large-scale glaciation event may have caused the extinction, as well as an increase in ocean acidification due to increased volcanic activity (“Ordovician Extinction”). This was 374million years ago. It’s the third-largest ever mass extinction. It is thought that the extinction was caused by a combination of an increase in sea level and anoxia, which refers to the depletion of oxygen levels in the ocean (“Devonian Extinction”). Permian Extinction, which took place around 252 millions years ago, was the most severe and devastating natural extinction in Earth’s history. It is believed that a combination of volcanic eruptions, a decrease in sea level, and climate change may have caused the extinction (“Permian Extinction”).

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