For decades, scientists have conducted research centered around the five major mass extinctions that have shaped the world we live in. The extinctions date back more than 450 million years with the Late Ordovician Mass Extinction, or LOME, to the deadliest extinction, the Late Permian extinction 250 million years ago that wiped out over 90 percent of species. Over the years, scientists have figured out the main causes of the mass extinctions, which include massive volcanic eruptions, global warming, asteroid collisions and acidic oceans as likely culprits. Other factors sure to play a part include methane eruptions and marine anoxic events -- when oceans lose life-supporting oxygen. The events that triggered the Late Ordovician Mass Extinction of marine animals and plants has largely remained a mystery until now. The Ordovician was a dynamic time interval in Earth history that recorded a major increase in marine biologic diversity and a greenhouse-to-icehouse climatic transition. Researchers believe this cooling period, which culminated in the first Phanerozoic glaciation led to the LOME. Now, a team of researchers has deciphered geochemical evidence left behind in marine limestone sediment that suggests this extinction was caused by a period of global cooling that created a global marine anoxic event.
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