With more than 29 million cubic kilometers (7 million cubic miles) of ice and snow, the Antarctic Ice Sheet is so massive that its weight depresses the underlying crust by 900 meters (nearly 3,000 feet). New snow that collects on the ice sheet's surface causes the ice beneath it to spread out and move along the slope of the land. In this video segment adapted from NOVA, a team of glaciologists carves into one glacier on the East Sheet to monitor the nature and speed of its movement.