Nature
Icebergs should be distinguished from polar pack ice, which is frozen sea water, and from ice islands, which are large areas of consolidated multi-year pack ice. An iceberg is a large mass of ice which has broken off and drifted from parent glaciers or ice shelves along polar seas. Icebergs drift with ocean currents into shipping lanes where they constitute a hazard. In polar seas their presence, together with pack ice, may prevent normal shipping movements.