An iceberg is ice that broke off from glaciers or shelf ice and is floating in open water

A tabular iceberg

Huge tabular icebergs, calved from the ice shelf in the Southern Ocean's Weddell Sea.

To be classified as an iceberg, the height of the ice must be greater than 16 feet (five meters) above sea level and the thickness must be 98-164 feet (30-50 meters) and the ice must cover an area of at least 5,382 square feet (500 square meters).

There are smaller pieces of ice known as “bergy bits” and “growlers.” Bergy bits and growlers can originate from glaciers or shelf ice, and may also be the result of a large iceberg that has broken up. A bergy bit is a medium to large fragment of ice. Its height is generally greater than three feet (one meter) but less than 16 feet (five meters) above sea level and its area is normally about 1,076-3,229 square feet (100-300 square meters). Growlers are smaller fragments of ice and are roughly the size of a truck or grand piano. They extend less than three feet (one meter) above the sea surface and occupy an area of about 215 square feet (20 square meters).

Icebergs are also classified by shape, most commonly being either tabular or non-tabular. Tabular icebergs have steep sides and a flat top. Non-tabular icebergs have different shapes, with domes and spires.

Icebergs are monitored worldwide by the U.S. National Ice Center (NIC). NIC produces analyses and forecasts of Arctic, Antarctic, Great Lakes, and Chesapeake Bay ice conditions. NIC is the only organization that names and tracks all Antarctic Icebergs.

For more information:
U.S. National Ice Center