Iceberg

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An iceberg is a large piece of ice from freshwater that has broken off from a snow-formed glacier or ice shelf and is floating in open water.[1] It may subsequently become frozen into pack ice. Alternatively, it may come to rest on the seabed in shallower water, causing ice scour (also known as ice gouging) or becoming an ice island.

Contents

Etymology

The word "iceberg" is a partial loan translation from Dutch ijsberg, literally meaning ice mountain,[2] cognate to Danish Isbjerg, German Eisberg, Low Saxon Iesbarg and Swedish/Norwegian Isberg.

Overview

Because the density of pure ice is about 920 kg/m³, and that of sea water about 1025 kg/m³, typically only one-ninth of the volume of an iceberg is above water. The shape of the underwater portion can be difficult to judge by looking at the portion above the surface. This has led to the expression "tip of the iceberg", for a problem or difficulty that is only a small manifestation of a larger problem.

Icebergs generally range from 1 to 75 metres (3–250 ft) above sea level and weigh 100,000 to 200 000 tons. The tallest known iceberg in the North Atlantic was 168 metres (550 ft) above sea level, reported by the USCG icebreaker East Wind in 1958, making it the height of a 55-story building. These icebergs originate from the glaciers of western Greenland, and may have an interior temperature of -15 to -20°C (5 to -4 °F).[3]

Though usually confined by winds and currents to move close to the coast, the largest icebergs recorded have been calved, or broken off, from the Ross Ice Shelf of Antarctica. Iceberg B-15, photographed by satellite in 2000, measured 295 km long and 37 km wide (183-23 mi), with a surface area of 11,000 km² (4,250 mi²). The mass was estimated around three billion tonnes. The largest iceberg on record was an Antarctic tabular iceberg of over 12,000 sq mi (208 miles long and 60 miles wide) sighted 150 miles west of Scott Island, in the South Pacific Ocean, by the USS Glacier on November 12, 1956. This iceberg was larger than Belgium.[4][5]

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