Great Dying, a catastrophic event that happened some 250 million years ago led to extinction of 90 percent of all marine life and nearly three-quarters of terrestrial plants and animals.
Was it a sudden extinction triggered by a meteorite’s impact or was it something else? Researchers led by Peter Ward of the University of Washington, who examined the Karoo Basin of South Africa, employing chemical, biological and other types of analysis, say that the mass extinction may have been triggered by a volcanic eruption.
They studied the extinction rate in the sedimentary layers in the basin. The results were those obtained from similar layers in China which were earlier examined for marine extinction that happened in the same time span.
The 1,000-foot-thick exposed section of sediment showed a gradual extinction over about 10 million years. Then suddenly there was a sharp rise in the extinction rate that remained so for 5 million more years. From this the team has speculated that the extinctions may have been the result of global warming and oxygen deprivation for extended time.
The team says that Siberia at that time had massive volcanoes that led to global warming while geologic action leading to a drop in global sea levels.
"Once you expose a huge amount of underwater sediment to the atmosphere, two very bad things happen -- a huge amount of carbon in the sediments is released and also methane. Once [methane] hits the atmosphere, it's the most efficient greenhouse gas on the planet," says Ward.
