 Greenland's 'grand canyon' was part of a large river system before an ice sheet covered it millions of years ago, a new study says. Unlike the ice sheet covering Antarctica that sits atop numerous lakes, the Greenland Ice Sheet blankets a giant subglacial canyon nearly twice as long as the Grand Canyon located in Arizona. Scientists suggest the canyon—which runs as deep as half a mile (800 meters) and as long as 466 miles (750 kilometers)—is paleofluvial, meaning it originated as a system of rivers in Greenland's hard bedrock surface. The canyon lacks features that would signal it was formed by glaciers, suggesting that its predates the initial appearance of glaciers there about 38 million years ago, according to the team led by Jonathan Bamber, a glaciologist at the University of Bristol in Britain. The team concludes that water would have flowed through the canyon constantly until Greenland's island-wide ice sheet formed 3.5 million years ago. A formal presentation of the results is set to appear in Friday's issue of the journal Science.
– Scientists have—totally by accident—come across a hidden canyon that dwarfs the Grand one, the BBC reports. The researchers were using radar to map out Greenland's bedrock when they stumbled upon the 2,625-foot deep feature, which, at 500 miles, is longer than the Grand Canyon's 277 miles, Design & Trend notes. It's full of ice now—the stuff is up to two miles thick—but a river forged the canyon some four million years ago, predating the ice. Now, a little meltwater drains out of the northern end of the unseen canyon, which runs from central Greenland to its north coast. "With satellite images instantly available on a mobile phone we could assume that the Earth has been fully mapped, but there's clearly a lot left to discover," says a scientist. The canyon could also be bad news: Water moving under Greenland's ice could contribute to faster melting, the Christian Science Monitor notes. So are there more of these in the world? The lead researcher tells National Geographic he's now wondering what lies under the Antarctic Ice Sheet—which is 10 times the size of Greenland's.