Huge Canyon Discovered Under Greenland Ice 137
cold fjord writes with this news, straight from the BBC: "One of the biggest canyons in the world has been found beneath the ice sheet that smothers most of Greenland. The canyon — which is 800km long and up to 800m deep — was carved out by a great river more than four million years ago ... It was discovered by accident as scientists researching climate change mapped Greenland's bedrock by radar. The British Antarctic Survey said it was remarkable to find so huge a geographical feature previously unseen. The hidden valley is longer than the Grand Canyon in Arizona. ... The ice sheet, up to 3km (2 miles) thick, is now so heavy that it makes the island sag in the middle (central Greenland was previously about 500m above sea level, now it is 200m below sea level)."
More info (Score:3, Informative)
Giant Canyon Discovered Under Greenland Ice Sheet [nationalgeographic.com]
While flying over the ice sheet, scientists over the past three decades have measured the depths of the canyon using a radar system that operates at frequencies transparent to radio waves—from around 50 megahertz to 500 megahertz. A pulse of energy is sent down to penetrate through the ice, bounce off the bedrock, and travel back to the radar system. (Also read: "'Shocking' Greenland Ice Melt: Global Warming or Just Heat Wave?")
'Grand Canyon' of Greenland Discovered Under Ice Sheet [livescience.com]
Re:So just wondering... (Score:5, Informative)
Re:So just wondering... (Score:5, Informative)
Re:Why is it (Score:5, Informative)
that Greenland is called Green again?
Propaganda. Erik the Red named it that in 985 AD to get people to colonize it with him.
Re:So just wondering... (Score:4, Informative)
Millennia. The post-glacial rebound [wikipedia.org] is still happening in North America from the last ice age [wikipedia.org], and that was 10,000 years ago. The New Madrid Seismic Zone [wikipedia.org] is still active today, and experts agree that it has the potential to produce another very powerful earthquake.
Re:So just wondering... (Score:5, Informative)
In theory, if all the ice on Greenland melted, how long would it take Greenland to spring back up again? I'm presuming it wouldn't be instantaneous or even noticeable to a human on Greenland at the time (well, aside from the earthquakes that would almost certainly accompany such an event,) but are we talking years, decades, centuries, or longer?
It would be noticeable by humans over their life span.
You see this (in smaller scale) in places in Alaska where receding ice caps and the glaciers that flow from them slowly recede up the valleys and vegetation changes appear in the wake.
You also see the river flowing from the glaciers cutting deeper channels to the ocean. The glaciers flowed directly to the ocean earlier, now the glacier's nose is several miles upstream. The river channels "grow" high banks as you travel away from the glacier toward the ocean. This is a sign of uplifting land, (there are no longer and deposited soils being laid down in the area, yet the river banks grow steeper, and the river surface is within a few feet of mean high tide over the years.
Its not much, but you can see it over a period of 30 or 40 years if you are observant. Surveyors can measure it these days (even without GPS), relative to mean high-tide in those places where survey markers were installed decades ago.
Re:How accurate is the sea level rise figure? (Score:5, Informative)
The sea level rises because the stuff covering Greenland is ice. When it melts it flows into the ocean, raising sea levels. Greenland is around 2M km2, and the ice sheet is around 2km thick, so we're talking about 4 million cubic kilometers of water. Earth has around 361 sq kilometers of water, so spreading the water around the earth gives around 10 meters of ice on each meter of water, or around 9 meters of water. In other words, (1) greenland is huge, and (2) the sea level rise is purely ice flowing into sea and has nothing to do with geological changes.
Greenland rebounding does absolutely nothing because the "extra" volume is not taken out of the ocean. The water doesn't suddenly jump back up on the land.
(arctic ice melting does not affect sea levels because the weight of the ice is already displacing water. Antarctic ice and glaciers on land are in the same situation as greenland ice)
Re:Science schmience (Score:5, Informative)
http://www.chem.tufts.edu/science/franksteiger/grandcyn.htm [tufts.edu]
AiG's claim was long ago debunked. At this point, the Weekly World News is probably a more reliable source of information than the lying mentally ill nutbars who write for AiG.
Re:So just wondering... (Score:3, Informative)
"The geomorphology of the region is largely shaped by the combined processes of glaciation, glacial retreat and the emergence of new land from the sea which continues today at a rate of 0.9 m per century."
Source: http://whc.unesco.org/en/list/898 [unesco.org]