A 278-square-mile iceberg broke off from Antarctica's Pine Island Glacier on Monday and is floating in the Amundsen Sea. Scientists had been observing two large cracks in the Pine Island glacier since 2011, but they are still unsure about the process by which a glacier breaks. "Glaciers are constantly in motion. They have their very own flow dynamics. Their ice is exposed to permanent tensions and the calving of icebergs is still largely unresearched," said team researcher Angelika Humbert.