A: In Antarctica, there are large floating sheets of ice, called shelf ice. Shelf ice extends into surrounding seas and produces vast plate-like icebergs when the edges of the shelf ice calve. Some of these icebergs have the lenghts of over 150 kilometres. Their flat tops may stand up to 200 metres above the ocean surface, although most rise less than 100 metres above sea level.The underwater portion of an iceberg is even more impressive: depending on the amount of rock material an iceberg may be carrying, as much as 90% of its mass will be below waterline.

In August 1991, for example, an iceberg the size of Connecticut (13000 square kilometres) broke loose from the ice shelf in the Weddell Sea. Once they are created, ocean currents driven by strong winds carry the icebergs to the north, where they disintigrate by melting. Because this region is not a major shipping route, the icebergs pose no real navigation hazard.However, there have been some disasters caused by icebergs, like the one with Titanic, which sank on her maiden voyage on 15th April 1912. Ships sighting these gigantic bergs, which can extend across the horizon, have often mistaken them for land!

Click here to return to the main menu.