Some of the biggest icebergs in the world break off from Antarctica’s ice shelves.
One iceberg, called B15A, was over 115 kilometers long and the same
size as Jamaica. Because the density of the freshwater ice is slightly
less than that of the surrounding seawater, only 10 percent of an
iceberg is typically visible above the water—hence the saying, “tip of
the iceberg”. Icebergs gradually melt as they drift farther away or
become grounded in shallow water. Here they can be sculpted by the waves
and frozen into the sea ice to form huge towers of ice.
Video: British Antarctic Survey
Text: British Antarctic Survey and WGBH Educational Foundation