Fog and icebergs are two of the greatest natural dangers to ships. How icebergs form and melt Explorers have written vivid descriptions of the color and beauty of icebergs, and compared them to towers, spires, pyramids, cathedrals, and palaces. But this is only a small part of the whole iceberg. 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. North Atlantic icebergs come from the island of Greenland. A huge ice sheet covers nearly all of Greenland. Long tongues of ice extend from the edge of this ice sheet into the sea. Cracks in the ice, and the action of rough sea waves, cause the icebergs to break off from the ice tongues.