text: Buried thousands of feet under Summit, the highest point on Greenland's ice sheet, is a soil born before humans ever walked on 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 today (April 17) 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 under Summit has been buried for 2.7 million years, then the discovery implies the ice sheet has never fully melted, even when the Earth went through an incredible natural warming swing 130,000 years ago — one as warm as this century's predicted climate change. 
   
   "Now we know that it's unlikely the ice sheet has disappeared for significant periods of time in the last 3 million years, at least at this one pinprick on this big island," Bierman told Live Science. "Now human activity may spell the end of it." 
   
   New look at old ice 
   
   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 meters) GISP2 ice core records more than 100,000 years of past climate history, but until now, no one had examined the dirt in the ice at the bottom of the drill hole. (The ice is archived at the National Ice Core Laboratory in Denver, Colo.) 
   
   "I was asking a really different question than people who look at ice cores," Bierman said. "I was looking for a history of landscapes in ancient Greenland, and that mindset wasn't there 20 years ago. It's the evolution of science — you're always coming up with new hypotheses to test," he said. 
   
   Piece of the GISP2 ice core showing silt and sand embedded in ice. Soon after this picture was taken, the ice was crushed in the University of Vermont clean lab and the sediment was isolated for analysis. Credit: Paul Bierman, University of Vermont 
   
   Bierman and his co-authors teased out the sediment locked in the frozen ice, and deciphered its history with a well-established geochemical technique called beryllium-10 dating. 
   
   Beryllium-10 is a radioactive isotope produced by cosmic rays (high-energy particles that rain down on Earth from space). The beryllium-10 isotopes help researchers gauge the age of landscapes, because the isotopes only form in rocks and soil exposed at the surface; cosmic rays can't penetrate thick ice or deeply buried rocks. Counting the number of beryllium-10 isotopes gives an estimate of how much time a rock or soil spent at the surface, bombarded by cosmic rays. 
   
   Bierman said he was stunned by the sky-high levels of beryllium-10 in the soil from the GISP2 ice core. 
   
   "Our eyes just lit up. It was completely unexpected and one of the few times I've been totally surprised in my career," Bierman said. 
   
   The frozen soil contains millions of beryllium-10 atoms, at a level comparable to other long-lived Arctic landscapes, such as tundra soil in Alaska, the researchers said. 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. 
   
   Basal ice, part of the Greenland Ice Sheet Credit: Paul Bierman, University of Vermont 
   
   Persistence of land 
   
   Of course, that begs the question of why Greenland's glaciers didn't grind away the ancient soil. The answer: Mounting evidence suggests many ice sheets are frozen to their beds. The ice does flow, but it deforms like glass or warm plastic above a base that is stuck to the ground. In the GISP2 ice core, the bottom 30 to 50 feet (10 to 15 m) is frozen to bedrock, and the ice above is a whirl of folded, deformed layers, Bierman said. These deforming ice sheets are called cold-based glaciers, while those that erode their rocky bottoms with water and ice are known as warm-based glaciers. [The Power of Ice: Photos of Glacier Erosion] 
   
   Previous work by Bierman's students found that some Greenland glaciers protect the land like armor, preserving landscapes that were 800,000 years old. 
   
   Bierman and his colleagues are now searching for ancient landscapes in Antarctica, though the researchers must reach back further in time because the continent froze earlier than Greenland. 
   
   "The bottom of an ice sheet can preserve some really old landscapes," Bierman said. 
   
   Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook and Google+. Original article at Live Science's Our Amazing Planet. ||||| Soil frozen for 2.7 million years beneath the Greenland ice sheet has provided clues about its history. 
   
   Frozen in time, the soil beneath an ancient tundra has been uncovered and tested, with scientists discovering that "Greenland really was green" at one point. 
   
   The tundra was discovered in 2013 and has been explored by scientists from the University of Vermont, who believe that the ice sheet is much older than previously thought, having endured previous periods of global warming. 
   
   Published in the journal Science, the researchers said they were surprised to find the landscape below preserved two miles of ice. "We found organic soil that has been frozen to the bottom of the ice sheet for 2.7 million years," research Paul Bierman said. 
   
   Study co-author Dylan Rood, from the Scottish Universities Environmental Research Centre and the University of California, Santa Barbara, added: "The ancient soil under the Greenland ice sheet helps to unravel an important mystery surrounding climate change. How did big ice sheets melt and grow in response to changes in temperature?" 
   
   Findings suggest that even during the warmest periods of history, the ice sheet at the centre of Greenland remained frozen, meaning the land has stayed hidden and unchanged for millions of years. 
   
   "[It's] a refrigerator that's preserved this antique landscape," Bierman said. 
   
   Scientists take huge interest in the stability of the Greenland ice sheet as it will fundamentally influence sea level rises resulting from manmade climate change. Instead of eroding the land beneath, the sheet has been frozen to the ground, the authors said. 
   
   The scientists tested 17 ice samples from the lowest 40ft of the ice core extracted from the glacier in 1993. From the sediment, the researchers extracted a rare form of the element beryllium. 
   
   This element is formed by cosmic rays and falls from the sky and becomes stuck to soil and rock. The longer the soil is exposed, the more beryllium-10 it accumulates, meaning it acts as a geological clock. 
   
   At first the team was only expecting to find eroded soil, they wrote: "We thought we were going looking for a needle in haystack. It turned out that we found an elephant in a haystack." 
   
   The beryllium concentrations could only have been found in soils that have developed over hundreds of thousands of years, if not millions: "The soil had been stable and exposed at the surface for somewhere between 200,000 and one million years before being covered by ice," said Ben Crosby, a member of the research team from Idaho State University. 
   
   Rood added: "Greenland really was green! However, it was millions of years ago. Greenland looked like the green Alaskan tundra, before it was covered by the second largest body of ice on Earth."
target: – The soil under the highest point of the Greenland Ice Sheet, scientists have learned, is 2.7 million years old, LiveScience reports. In other words, the silt buried under thousands of feet of ice "has been preserved from beyond the dawn of humankind," says Paul Bierman, who determined the soil's age through a geochemical dating process. The findings also suggest Greenland wasn't always as frosty as it is today: Instead, it was a tundra for between 200,000 and one million years before it was encased in ice. It was once home to bits of forest, the scientists found using offshore plant DNA. In other words, as the International Business Times has it, "Greenland really was green." The Greenland Ice Sheet that's there now, however, has been remarkably durable: The findings imply that it made it through a strong period of warming some 130,000 years ago. "It's unlikely the ice sheet has disappeared for significant periods of time in the last three million years, at least at this one pinprick on this big island," Bierman says. "Now human activity may spell the end of it." (What else lies under Greenland's ice? A canyon that dwarfs the Grand Canyon, an aquifer holding 100 billion tons of water, and two huge lakes.)