for National Geographic News
Plants, insects, and other life-forms dating back 14 million years have been found on Antarctica, a new study says.
The specimens—some of which contain organic tissue—help paint a picture of a temperate Antarctica where glacial lakes were surrounded by trees and swarmed with buzzing blackflies.
Researchers found the freeze-dried remains of mosses, algae, small crustaceans, and beetles in the McMurdo Dry Valleys, where glacial lakes once existed.
The site also contains a layer of potassium-rich volcanic ash, which can be precisely dated, allowing researchers to pinpoint for the first time how long ago the plants and animals lived.
"We have documented the timing and magnitude of the tremendous climate shift in Antarctica," said study co-author David Marchant, a professor of earth sciences at Boston University.
"The transition marks a shift from warm, temperate glaciers with patches of fringing [forest] to tundra to today's cold polar glacier, set within a barren polar desert."
The researchers determined the ash fell in the lake 14.07 million years ago. Other nearby ash deposits show that most liquid water in the area froze by 13.9 million years ago.
At some point during that 200,000-year interval—brief by geologic standards—the average summertime temperature plunged by about 14 degrees Fahrenheit (8 degrees Celsius), said Adam Lewis, a geoscientist at North Dakota State University and co-author of the report.
"There's a climate boundary, and it is between those two dates," Lewis said.
"Everybody knows that Antarctica used to hold life, but nobody has ever been able to put their finger on the point in time when that life got snuffed out by decreasing temperatures and growing ice sheets."
The summertime temperatures in the McMurdo Dry Valleys during the temperate period would have hovered around 41 degrees Fahrenheit (5 degrees Celsius)—31 degrees Fahrenheit (17 degrees Celsius) warmer than the summer averages of today.
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