Yale Environment 360: Researchers have discovered craters left behind when two lakes under the Greenland ice sheet rapidly drained recently -- an indication that a massive amount of meltwater has started overflowing the ice sheet's natural plumbing and is causing "blowouts" that drain lakes away, they say. One of the two lakes once held billions of gallons of water and emptied to form a mile-wide crater in just a few weeks, researchers report in the journal The Cryosphere. The other lake, described this week in the journal...