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Sunday, September 1, 2013

Canyon longer than Grand Canyon found buried under Greenland ice sheet

3-D view of the subglacial canyon, looking to the southeast from the north of Greenland
One of the biggest canyons in the world has been discovered buried beneath more than two miles of ice in Greenland.

The hidden canyon is up to half a mile deep, six miles wide and stretches for 466 miles beneath the country’s giant ice sheet.

It is thought to have been carved out by a meandering river more than four million years ago – at a time before ice covered the area and humans were just beginning to evolve from primates. 

Researchers at Bristol University, the British Antarctic Survey and Nasa stumbled across the canyon when using airborne radar to image the landscape beneath the ice.

They believe the buried valley, which is longer than the Grand Canyon in Arizona, may still contain running water and acts as an important channel for melt water beneath the ice.

It winds its way from the centre of Greenland to a deep fjord on the northern coast, and water still trickles out into the Arctic Ocean from beneath the glaciers.
The scientists believe the subglacial canyon is longer than the Grand Canyon in Arizona 
Scientists said this probably explains why they have not found lakes beneath the ice sheet there, while beneath the ice in Antarctica they are relatively common.

Before the ice covered Greenland, the canyon probably contained a mighty river that poured water into the sea, the scientists who discovered it said.

They said the discovery suggested there are many more impressive hidden landscapes still to be found beneath ice sheets around the world.

Similar work in Antarctica has also revealed enormous lakes and entire mountain ranges locked beneath the ice.

Professor David Vaughan, ice2sea coordinator based at the British Antarctic Survey in Cambridge who was one of the authors of the study, said: "A discovery of this nature shows that the Earth has not yet given up all its secrets.

“A 750km canyon preserved under the ice for millions of years is a breathtaking find in itself, but this research is also important in furthering our understanding of Greenland’s past.

“This area’s ice sheet contributes to sea level rise and this work can help us put current changes in context."
3-D view of the subglacial canyon, looking to the southeast from the north of Greenland
The canyon was discovered after scientists pieced together thousands of bits of data from airborne radar surveys.

Researchers have been flying over Greenland over the past two decades, beaming radio waves through the ice to image the rock beneath.

At the right frequencies, ice is transparent to radio waves but is reflected back by the solid bedrock the ice sheet sits above.

The aerial surveys build up thin glimpses of the landscape beneath the ice that can then be pieced together to form a detailed, three dimensional map.

Professor Jonathan Bamber, from the school of geographical sciences at Bristol University who was the lead author of the study which is published in the journal Science, said researchers were surprised when they saw the size of the so called "mega-canyon" as they put the data together.

He said: “It is a huge feature and it was quite a surprise to all of us that it was really there.

“We are pretty excited and amazed when we discovered this huge, undiscovered feature.”

He added: "With Google Streetview available for many cities around the world and digital maps for everything from population density to happiness one might assume that the landscape of the Earth has been fully explored and mapped. Our research shows there's still a lot left to discover."

Source: http://www.telegraph.co.uk

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