Scientists have speculated that mass extinctions might be precipitated by major volcanic eruptions that may have sufficient effect on climate to cause enough cooling to collapse of ecosystems and cause mass extinctions AFP/JIJI Photo 2000
Scientists have speculated that mass extinctions might be precipitated by these volcanic eruptions. For those eruptions to have had a sufficient effect on climate to cause cooling significant enough to lead to the collapse of ecosystems and the extinction of many species, scientists have said that they would have had to have been capable of thrusting gases and particles up into the stratosphere where they would block out sunlight.
Computer models suggested that flood basalt eruptions could cause this kind of effect on climate, but recent changes in scientists' ideas of the speed at which flood lavas are erupted has drawn into question these original findings.
Now, a University at Buffalo geologist has reexamined the issue and shown that it is indeed very likely that huge flood basalt eruptions caused dramatic global-scale climate shifts and mass extinctions, even if lava is erupted relatively slowly.
Elisabeth Parfitt, Ph.D., UB assistant professor of geology, described results of her research here today (Nov. 16, 2000) at the annual meeting of the Geological Society of America.
Parfitt's computer models are the first to show that 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, causing gases and fine ash to be carried into the upper atmosphere, even in the case where an eruption might not generate sufficient heat to cause clouds of gases and particles to reach high enough into the atmosphere to effect the global climate.
Some of these massive sheets of lava measured as large as 200 kilometers, or 130 miles, long.
"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."
Parfitt explained that these huge eruptions are like much bigger versions of basaltic eruptions, such as those going on now in Hawaii. She added that a large part of Washington state is covered by flood basalt lava, which erupted there about 16 million years ago.