Buried thousands of feet under Summit, the highest point on Greenland's ice sheet, is a soil born before humans walked the earth. The 2.7-million-year-old silt is a remnant of the verdant tundra that covered Greenland before it was entombed in ice, researchers report Thursday in the journal Science.
Pollen and plant DNA buried in the seafloor offshore of Greenland also suggest the island once had tundra and patchy forest, similar to today's high Arctic.
The new findings hint that at Summit, the tundra landscape was open to the sky for 200,000 years to 1 million years before ice covered it. [In Photos: See Greenland's Ancient Landscape]
"There was a really stable landscape on Greenland before the ice sheet came," said lead study author Paul Bierman, a geomorphologist at the University of Vermont. "This landscape has been preserved from beyond the dawn of humankind."
The new results also mean the Greenland Ice Sheet gets a nod for endurance. If the soil was buried 2.7 million years ago, then the discovery implies the ice sheet has never fully melted, even when Earth went through a warming swing 130,000 years ago — one as warm as this century's predicted climate change.
The ancient soil was pulled from beneath the Greenland Ice Sheet in 1993 during the GISP2 deep-drilling project to reach the bedrock beneath Summit. The 10,019-foot-long (3,052-meter-long) GISP2 ice core records more than 100,000 years of climate history, but until now, no one had examined the dirt in the ice at the bottom of the drill hole.
Bierman deciphered the sediment's history with a well-established geochemical technique called beryllium-10 dating. The readings showed that the sediment had been exposed at the surface for much longer than expected.
Only the interiors of Africa and Australia contain older landscapes, having escaped the erosive power of the Earth's recent ice ages. Soils in these hot continental interiors are many millions of years old.
— Becky Oskin, LiveScience
This is a condensed version of a report from LiveScience's Our Amazing Planet. Read the full report. Email Becky Oskin or follow her on Twitter. Follow Our Amazing Planet on Twitter, Facebook and Google+.
