iceberg

a piece of ice that has broken off from the end of a glacier that terminates in water.
Lamplugh Glacier, in Glacier Bay Alaska, shows the terminus of a typical tidewater glacier. The terminus of the glacier is heavily crevassed and jagged, and is calving small icebergs. For scale, note the man standing on the rocks in the foreground (near the center of the photograph). This photograph was taken in 1941. (Photo courtesy of W. O. Field, archived at the World Data Center for Glaciology, Boulder, CO.)