Icebergs

Icebergs form where chunks of ice break away from a glacier as it flows into the sea. The sun and wind melt the top of an iceberg. The bottom, which is under water, melts much more slowly. As the top melts away, leaving the bottom hidden beneath the surface, the iceberg becomes extremely dangerous to ships.

Icebergs are huge masses of ice that break off the lower end of a glacier and fall into the sea. These masses are made of frozen fresh water. Fog and icebergs are two of the greatest natural dangers to ships.

Large icebergs weigh more than 1 million tons (910,000 metric tons), and some are many miles or kilometres long. The biggest ones tower as much as 400 feet (120 meters) above the surface of the ocean. But this is only a small part of the whole iceberg. Only one-seventh to one-tenth of the iceberg's total mass is above water.

The white color of icebergs is caused by tiny, closely spaced gas cavities throughout the ice. When the sun is shining, streams of water form on the slopes of icebergs and drop over their edges in waterfalls. Icebergs often carry away large boulders and quantities of gravel from their glaciers. These are carried for long distances and finally dumped in the sea when the iceberg melts.

Learn more about icebergs.