When valley glaciers reach the sea or a lake, large pieces can break off, or calve , and form icebergs. Usually these pieces are irregularly shaped and contain lots of rock material. Irregular iceberg calved from a valley glacier. Ice Tongues Ice draining from the ice sheet through outlet glaciers , ice streams , or valley glaciers may extend, floating, into the sea. These seaward extensions are called ice tongues.
Ice tongues can rapidly change size and shape.
Eventually, the tongue can become too long. Tides, waves and storms slowly weaken the link between the tongue and the drainage system. The tongue, or a piece of it, will break off and float to sea as an irregularly shaped iceberg. Drygalski Ice Tongue is the largest ice tongue in Ross Sea. Aerial view looking onto Drygalski Ice Tongue as it floats on the ocean.