Sept. 9 (UPI) -- Around 260 million years ago, Earth experienced a previously underestimated severe mass-extinction event, according to a new study.
Scientists have previously pinpointed five major mass-extinction events, each ending major geological periods: the Ordovician, 443 million years ago; the Late Devonian, 372 million years ago; the Permian, 252 million years ago; the Triassic, 201 million years ago; and the Cretaceous, 66 million years ago.
For the latest study, published this week in the journal Historical Biology, scientists examined fossil records from the Guadalupian epoch, or Middle Permian period, which stretched roughly from 272 to 260 million years ago. Their analysis revealed previously underestimated losses of plant and animal genera on land and in the sea.
"It is crucial that we know the number of severe mass extinctions and their timing in order to investigate their causes," Michael Rampino, a professor biology at New York University, said in a news release. "Notably, all six major mass extinctions are correlated with devastating environmental upheavals -- specifically, massive flood-basalt eruptions, each covering more than a million square kilometers with thick lava flows."
Researchers determined the loss of life coincided with the Emeishan flood-basalt eruptions, which produced the Emeishan Traps, a massive, multi-layered igneous rock rock formation found in southwest China.
"Massive eruptions such as this one release large amounts of greenhouse gases, specifically carbon dioxide and methane, that cause severe global warming, with warm, oxygen-poor oceans that are not conducive to marine life," Rampino said.
According to Rampino and his colleagues, the previously underestimated end-Guadalupian extinction event should be placed in the same category as the other five major mass extinctions, bringing the total to six. That would make the current loss of plant and animal life on Earth -- a pattern many scientists estimate is the beginnings of a sixth mass extinction event -- the seventh mass extinction.