An iceberg is a large block of floating ice. A majority of the icebergs in the North Atlantic come from about 100 iceberg-producing glaciers along the Greenland coast, and a few originate in the Eastern Canadian Arctic Islands. The glaciers of western Greenland where 90 percent of Newfoundland’s icebergs originate are among the fastest moving in the world, drifting up to 4.3 miles (7 kilometers) per year. Although some Antarctic icebergs are more than 60 miles (100 kilometers) long, they look a lot smaller because most of the iceberg floats underwater. This can be dangerous to ships, whose navigators may underestimate the length or depth of the iceberg.