for National Geographic News
Huge tracts of prehistoric rain forest ravaged by global warming more than 300 million years ago have been found preserved underneath the U.S. Midwest, according to scientists.
The fossilized forests, including one covering 39 square miles (100 square kilometers), were discovered in coal mines in eastern Illinois by a team of international researchers.
In 2007, the same research team found a four-square-mile (ten-square-kilometer) fossil forest near the town of Danville (Illinois map).
(Related: "Giant Fossil Rain Forest Discovered in Illinois" [April 24, 2007])
Five additional petrified forests have now been found, scientists said. The six tracts span a period of about two million years near the end of the Carboniferous period (359 to 299 million years ago.)
The finds represent the earliest rain forests to appear on Earth and date back to eras just before and after intense global warming, study leader Howard Falcon-Lang, of the University of Bristol in the U.K., announced yesterday at the British Association Science Festival in Liverpool, U.K.
"We probably have six forests all stacked up on top of each other," Falcon-Lang said. "Three of the forests predate global warming and the rest follow it, so we can compare the ecology of those rain forests to see what the effect of global warming was."
During that period the Earth's climate flipped from being covered with large polar icecaps to a greenhouse state that was completely ice-free, he added.
The fossilized plants suggest sudden dramatic change occurred, with dense vegetation and trees up to 40 meters (130 feet) high being largely replaced by tree fern species, Falcon-Lang said.
"Although the change was sudden, we don't know how sudden," Falcon-Lang said. "Was it a decade, was it a hundred years, or was it a thousand years?"
The study team says detailed analysis of the fossil forests should answer this question.
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