Environment. Scooped by Odin Prometheus on Scoop.it! Giant Canyon Discovered Under Greenland Ice Sheet. From news.nationalgeographic.com - August 30, 12:42 PM The Greenland Ice Sheet sits atop a canyon nearly twice as long as the Grand Canyon. The Erebus Glacier Tongue in Greenland is surrounded on three sides by sea water during the summer thaw. But scientists say the majority of the Greenland Ice Sheet sits atop a canyon twice as long as the Grand Canyon. Photograph by George Steinmetz, National Geographic. Jaclyn Skurie National Geographic Published August 29, 2013 Imagine if you could pick up the Greenland Ice Sheet and see what lies beneath. Surely 1.7 million square kilometers of slowly thawing ice must rest on a massive pool of melted water, right?