iceberg

An iceberg is a piece of freshwater ice more than 15 m long that has broken off a glacier or an ice shelf and is floating freely in open (salt) water. Smaller chunks of floating glacially-derived ice are called "growlers" or "bergy bits". The sinking of the ''Titanic'' in 1912 led to the formation of the International Ice Patrol in 1914. Much of an iceberg is below the surface, which led to the expression " tip of the iceberg" to illustrate a small part of a larger unseen issue. Icebergs are considered a serious maritime hazard.

Icebergs vary considerably in size and shape. Icebergs that calve from glaciers in Greenland are often irregularly shaped while Antarctic ice shelves often produce large tabular (table top) icebergs. The largest iceberg in recent history (2000), named B-15, measured nearly 300 km × 40 km. The largest iceberg on record was an Antarctic tabular iceberg of over [] sighted west of Scott Island, in the South Pacific Ocean, by the USS Glacier (AGB-4), USS ''Glacier'' on November 12, 1956. This iceberg was larger than Belgium. Big icebergs are also often compared in size to the area of Manhattan.

Etymology

The word ''iceberg'' is a partial loan translation from the Dutch word ''ijsberg'', literally meaning '' ice mountain'', cognate to Danish ''isbjerg'', German ''Eisberg'', Low Saxon ''Iesbarg'' and Swedish '' isberg''.

Overview

Typically about one-tenth of the volume of an iceberg is above water, which follows from Archimedes's Principle of buoyancy; the density of pure ice is about 920  kg/m³ (57 lb/cu ft), and that of seawater about . The contour of the underwater portion can be difficult to judge by looking at the portion above the surface.

The largest icebergs recorded have been calved