The End-Permian mass extinction was huge, the largest of the five major mass extinctions on the geological time scale. It happened approximately 245 million years ago and eliminated approximately fifty-four percent of marine families and possibly almost ninety-six percent of all marine species (Erwin, 69). Brachiopods, bryozoans, and stalked echinoderms were hit incredibly hard by the extinction by the bivalve and gastropod mollusks were hit reasonably hard (Stanley, 418). There are many theories that suggest what may have happened to cause the end-Permian mass extinction but it has not been unanimously decided among scientists what really happened. I have studied articles written by various people that discuss what they believe to have been the cause. There articles contain some types of evidence to back up their theories but there may not be enough evidence to confidently say that their theory is the right one.
The possible theories for extinction remain somewhat constant through the essays I have read. Regardless of what one author believes is true, they typically mention other theories and how they could also be a possibility. There are five major theories to explain the extinction:.
1. Much evidence has been found to prove that oxygen levels in the ocean were incredibly low in deep and shallow ocean levels.
2. There was a dramatic rise in sea level.
3. A giant flood basalt in Siberia erupted.
4. The oxygen in the atmosphere dropped, resulting in global warming.
5. The atmospheres carbon cycle may have shifted separating organic carbon from the .
oceans. (Bowring, Erwin, and Isozaki, 8827).
According to Douglas Erwin, the extinction did not happen all at once time. In fact, he has said that it began near the end of the Guadalupian age and lasted into the Triassic period. This means that the extinction lasted for approximately five to eight million years. Erwin also states that this makes the end-Permian mass extinction the longest extinction during the Phanerozoic era.