Scientists have long believed that mass extinctions are caused by sudden global changes in climate.

Some of these events, like the one originally assumed to have wiped out the dinosaurs, occurred at around the same time as tremendous volcanic eruptions called flood basalt eruptions.

	Heat from massive lava flows, like this one at Kilauea volcano, Hawaii, have been found by Elisabeth Parfitt to cause climate shifts.
	Photo: J. D. Griggs

For that reason, scientists have speculated that mass extinctions might be precipitated by these volcanic eruptions.

But in order for those eruptions to have had an effect on climate, and therefore to have caused these mass extinctions, they would have had to have been capable of thrusting gases and particles up into the stratosphere where they could block out the sun. That would cause cooling significant enough to lead to the collapse of ecosystems and the extinction of many species.

A UB geologist has re-examined the issue and shown that it is very likely that huge flood basalt eruptions cause dramatic, global-scale climate shifts and mass extinctions, even when lava is erupted relatively slowly.

Elisabeth Parfitt, assistant professor of geology, will describe the results of her research on Nov. 16 in Reno, Nev., at the annual meeting of the Geological Society of America.

Parfitt's models are the first to show how massive sheets of lava produced by flood basalt eruptions millions of years ago generated such intense heat that they functioned as a secondary heat event, which can cause gases and fine ash to be carried into the upper atmosphere.

Surprisingly, her results show that the eruptions themselves may not generate sufficient heat to cause the eruption cloud to reach high enough into the atmosphere to effect the global climate.

"Because only eruptions which erupt lava very rapidly could have allowed volcanic plumes to reach the stratosphere, any impacts on climate would have been local or regional at best," she said.

However, her model demonstrates for the first time that massive sheets of lava-some as large as 200 kilometers, or 130 miles long-generated by these eruptions would have given off such intense heat that they would have caused particles and gases to reach the upper atmosphere, where their effects on climate would have been substantial.

"According to our models, these lava flows, which could be as hot as 1,200 degrees Centigrade when they are first erupted, could push ash and gas up to heights of 30 kilometers above the volcanic vent," said Parfitt.

"Sometimes volcanic eruptions don't form a mountain," she explained. "Instead, the magma shoots straight up through the earth's crust and is erupted from a crack, which might be as much as 100 kilometers long.

"These flood basalt eruptions often produced these massive sheets of lava, which can be as much as 100 or 200 kilometers (65 miles or 130 miles) long and they gave off a huge amount of heat."