The largest known iceberg in the North Atlantic was 168 metres (551 ft) above sea level, reported by the USCG icebreaker Eastwind in 1958, making it the height of a 55-story building. Icebergs or pieces of floating ice smaller than 5 meters above the sea surface are classified as "bergy bits" smaller than 1 meter-"growlers". Icebergs may reach a height of more than 100 metres (300 ft) above the sea surface and have mass ranging from about 100,000 tonnes up to more than 10 million tonnes. The largest icebergs recorded have been calved, or broken off, from the Ross Ice Shelf of Antarctica. Northern edge of Iceberg B-15A in the Ross Sea, Antarctica, 29 January 2001 Iceberg size classifications according to the International Ice Patrol Size class Big icebergs are also often compared in size to the area of Manhattan. The largest iceberg on record was an Antarctic tabular iceberg of over 31,000 square kilometres (12,000 sq mi) sighted 240 kilometres (150 mi) west of Scott Island, in the South Pacific Ocean, by the USS Glacier on November 12, 1956. The largest iceberg in recent history (2000), named B-15, measured nearly 300 km × 40 km. Icebergs that calve from glaciers in Greenland are often irregularly shaped while Antarctic ice shelves often produce large tabular (table top) icebergs. Icebergs vary considerably in size and shape. Icebergs are considered a serious maritime hazard. 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.
The 1912 loss of the RMS Titanic led to the formation of the International Ice Patrol in 1914. Smaller chunks of floating glacially-derived ice are called "growlers" or "bergy bits". Icebergs in Greenland as filmed by NASA in 2015Īn 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.