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Huge Canyon Discovered Under Greenland Ice
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)."
Centuries to millennia. Geologists are able to measure the ongoing rebound of North America from the retreat of the glaciers from the last ice age.
that Greenland is called Green again?
Propaganda. Erik the Red named it that in 985 AD to get people to colonize it with him.
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.
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