'Grand Canyon' of Greenland Discovered Under Ice

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The age of discovery isn't over yet. A colossal canyon, the longest on Earth, has just been found under Greenland's ice sheet, scientists announced this week in the journal Science.

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"You think that everything that could be known about the land surface is known, but it's not," said Jonathan Bamber, lead study author and a geographer at the University of Bristol in the United Kingdom. "There's still so much to learn about the planet."

On July 31, 2012, a satellite showed the large iceberg had nearly reached the mouth of the fjord that houses Greenland's Petermann Glacier.
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The great gorge meanders northward from Summit, the highest point in central Greenland, toward Petermann Glacier on the northwest coast, covering more than 460 miles (750 kilometers). Researchers think the ravine could be even longer, but they don't yet have the data to prove where the canyon peters out deep under the interior ice sheet. "It may actually go farther south," Bamber told LiveScience's OurAmazingPlanet. (See Photos of Mega-Canyon Under Greenland Ice Sheet)

The broad chasm is up to 2,600 feet (800 meters) deep and 6 miles (10 km) wide, similar to America's Grand Canyon in scale, the researchers said. The distinctive V-shaped walls and flat bottom suggests water carved the buried valley, not ice, Bamber said. Though it is not the world's deepest canyon, it's the longest, handily besting the 308-mile-long (496 km) Yarlung Tsangpo Grand Canyon in China.

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Many mysteries in what lies beneath

The discovery could raise as many questions as it answers. For instance, researchers have long puzzled over what happens to water under Greenland's interior ice sheet. Greenland bows inward like a soup bowl, yet water melting under the interior ice sheet seems to drain to the sea instead of pooling in the middle. Bamber and his colleagues think the northern canyon may route some of the meltwater into the ocean.

The great river channel could explain the missing lakes under Greenland's interior ice sheet. The weight of the ice sheet pushes down the island's middle into a bowl-shaped basin. Given this saggy middle, scientists have long wondered why Greenland isn't filled with buried lakes, like Antarctica's Lake Vostok and Lake Whillans. The northern part of the canyon may drain meltwater, but farther inland, Bamber and his colleagues think the massive weight of ice pushes water elsewhere. (North vs. South Poles: 10 Wild Differences)

"It probably doesn't have water flowing through all of it today, given the interference by the ice overburden. However, when ice-free, water would channel through all of it," Siegert told LiveScience's OurAmazingPlanet.

And the newly discovered canyon could boost the breakup of one of the coastline's briskly retreating glaciers. The Greenland Grand Canyon dumps right into Petermann Glacier, which has dropped two massive icebergs in the past three years, each bigger than Manhattan.

"It's fair to say that a lot of work is now needed to work out the evolution of this feature and what it means for today's ice sheet," said study co-author Martin Siegert, a glaciologist at the University of Bristol. (Fly Over Greenland's Grand Canyon)

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