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Did Sea Level Flux Drive Mass Extinctions?

Marlowe Hood, AFP




Rising Tides



June 17, 2008 --
Mass extinctions that wiped out up to 90 percent of Earth's flora and fauna were driven in large part by shifting ocean levels, according to a study published in Nature.

Understanding what made many of the planet's living organisms rapidly die out at least five times over the last half billion years remains one of the great challenges in paleontology and biology.
Some theories point an accusing figure at the cooling effect of massive dust shrouds thrown into the atmosphere by volcanoes and asteroids crashing into Earth, or the warming caused by rising levels of carbon dioxide.
Other scientists highlight the role of disease and competition among species for limited resources.
But the new study suggests that it was the ebb and flow of sea levels and sediment over geologic time, rather than cataclysmic events, that doomed tens of thousands of species to extinction.

"The expansions and contractions of those environments have pretty profound effects on life on Earth," said Shanan Peters, a geologist at the University of Wisconsin-Madison and sole author of the study.
Since the beginning of life on Earth, some 3.5 billion years ago, there have been more than 20 mass extinction events, many involving single-cell organisms.

source: www.dsc.discovery.com