Harold Brenner, age 9, of Nampa, Idaho, for his question:
HOW ARE ICEBERGS FORMED?
Icebergs are giant masses of ice that break off the lower end of glaciers and fall into the sea. A large iceberg may weigh more than one million tons and it can measure many miles in length. The biggest ones can tower as much as 400 feet above the surface of the ocean.
Icebergs have sometimes been used by sailors as an emergency supply of drinking water.
Their white color 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 create waterfalls.
Icebergs often carry away large boulders and large amounts of gravel from their parent glaciers. These are carried for long distances and dumped in the sea when the iceberg melts.
North Atlantic icebergs come from the island of Greenland. A huge ice sheet, vith an average thickness of 5,000 feet, covers nearly all 700,000 square miles of Greenland. Long tongues of ice extend from the edge of the ice sheets into the sea. Cracks in the ice, and the action of rough sea waves, cause the icebergs to break off from these tongues.
Noise like great explosions and rolling thunder accompany the birth of an iceberg as it cracks loose. If it drops into an enclosed bay, it may cause huge waves.
Most icebergs in the North Atlantic drift across Baffin Bay and Davis Strait to the coast of Labrador. Some, however, are carried by the Labrador Current through the Newfoundland Banks into the Atlantic Ocean. Here icebergs melt quickly because of the abundance of both sunshine and warm ocean water.
As an iceberg breaks up, it forms small packs called ice floes. These chunks of ice usually disappear about 400 miles south of Newfoundland.
Many icebergs in the North Atlantic reach the routes of transatlantic liners in April, May and June. For this reason, most ships follov a more southerly course at this time of year than the one usually taken.
Antarctic icebergs drift to sea from the great Antarctic icecap. Some of then are many times larger than the largest found in the North Atlantic..
The largest iceberg ever seen in the Antarctic region was 60 miles wide and about 200 miles long, twice as big as Connecticut.
There is little that can be done to control icebergs. It is hard to destroy them by blasting or to steer them onto a course that would take them out of ocean shipping lanes. Actually, it is even difficult to approach an iceberg, because the submerged parts may tear open a ship's bottom.
Ships and airplanes report the position of moving icebergs to the International Ice Patrol.