The Larsen Ice Shelf is made of thick plates of ice that are fed by area glaciers. They float on the ocean around Antarctica. NASA has watched this shelf break up over the last decade. In 2002, a significant part of the shelf broke off into the ocean — the largest chunk to break off in more than 30 years. “Based on studies of ice flow and sediment thickness beneath the ice shelf, scientists believe that it existed for at least 400 years prior to this event,” reports NASA. Further, it “likely existed since the end of the last major glaciation 12,000 years ago.” Here is the Larsen Ice Shelf as imaged by NASA in 2004.