Tim Payton, age 8, of Kalispell, Mont., for his question:
HOW ARE ICEBERGS FORMED?
Icebergs are huge masses of ice that break off the lower end of glaciers and fall into the sea. A large iceberg may weigh more than 1 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 are formed by frozen fresh water. They form as chunks of ice break away from glaciers. Icebergs have sometimes been used by sailors as an emergency supply of 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.
North Atlantic icebergs come from the islands of Greenland. A huge ice sheet covers nearly all of Greenland. It has an area of about 700,000 square miles and an average thickness of the ice is 5,000 feet.
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 the tongues.
Noise like great explosions and rolling thunder accompany the beginning of an iceberg as it cracks loose. If the iceberg drops into an enclosed bay, it may cause huge waves.
Most of the icebergs in the North Atlantic drift across Baffin Bay and Davis Strait to the coast of Labrador. Some of them are carried by the Labrador Current through the Newfoundland Banks into the Atlantic Ocean. In this region of the ocean, the icebergs melt rapidly because of the sunshine and warm ocean water.
As an iceberg breaks up, it forms small packs called ice floes. These chunks of ice often disappear about 400 miles south of Newfoundland.
The greatest number of North Atlantic icebergs reach the routes of transatlantic liners in April, May and June. That is why most ships crossing the Atlantic at this time follow a more southerly course than the one they usually take.
Antarctic icebergs drift out to sea from the great Antarctic icecap. Some of them are many times larger than those found in the North Atlantic.
The largest iceberg ever seen in the Antarctic region was 60 miles wide and about 200 miles long. Its area of 12,000 square miles was twice as big as Connecticut.
There is little man can do to control icebergs. It is difficult to destroy them by blasting, or to steer them into a different course which 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.