Ice calving is the breaking off of chunks of ice at the edge of a glacier.  As you can see here, it is both spectacular and terrifying.

Video Summary

According to the Guinness Book of World Records, this is the largest calving event ever caught on tape. The calving event occurred in Greenland and lasted 75 minutes. Although most of the ice was underwater, the height of the ice (above the water) was about 300-400 feet. To give the calving scale, it’s as if the entire lower tip of Manhattan broke off. The thickness of the ice was equivalent to 3 times the height of buildings in lower Manhattan.