Dawn Lawson, age 13, of Pittsfield, Mass., for her question:

HOW ARE ICEBERGS FORMED?

Whenever glaciers of ice sheets reach the sea, the movement of the ice eventually pushes the end of the sheet into water which is deeper than the thickness of the glacier ice. Portions of the end of the glacier break off and form floating masses known as icebergs or bergs.

Icebergs are often of enormous size and may reach a height of about 300 to 500 feet above the surface of the sea. About 90 percent of the mass of an iceberg is beneath the surface, so that the visible portion of a berg is only a very small part of the total.

Icebergs are common in both the Arctic and Antarctic regions and are often carried into lower latitudes by sea currents, particularly in the North Atlantic Ocean. North Atlantic icebergs all come from the Great Greenland ice sheet and have been observed as far as about 2,000 miles from their origin.

After the sinking of the steamship "Titanic" in 1912, an iceberg patrol of the North Atlantic was instituted by 16 nations. The patrol, which includes the United States Coast Guard, tracks icebergs and reports their location to ships nearby.