The icebergs in the North Atlantic are large pieces of ice that have broken off from the glaciers of Greenland. Since frozen water is lighter than liquid water, the broken pieces float as icebergs on the sea. They are pointy and often interspersed with debris. In contrast, the icebergs in the South Atlantic are mostly flat. They are broken pieces of the flat sea ice, which surrounds the Antarctic. Icebergs can float for thousands of kilometres before they melt. Only one-ninth of an iceberg stays above the water. If the part above the water is 100 m high, then the part below is 800 m deep.