Menace Of The Sea Lanes

Ten thousand years ago, geologists say, the site of Stockholm, Sweden, was still covered with ice. Today, remains of the glaciers form the Greenland ice cap and cover countless islands in the far North. All told, there are about eight hundred thousand square miles of ice-covered land in the Arctic, plus an un-melting stretch of polar cap-ice over some two million square miles of the Arctic Sea. At the other end of the globe a sheet of five million square miles of ice covers the great south polar continent of Antarctica. Icebergs, which menace the sea-lanes, break away or are "calved" from these great remaining ice sheets. More than ten thousand icebergs break away from Greenland glaciers every year. Most of the bergs, which move well south in the Atlantic, come from western Greenland. These are not just small floating ice cakes—some of them rise five hundred feet out of the water and are hundreds of feet in length.

No one knows surely what caused the glacial period, although geologists have advanced several different theories to explain it. When the period was at its height, the great ice sheet reached as far south as the Ohio valley in what is now the United States, and as far south as Bavaria in Europe. Strangely enough, the glaciers did not join to form a continuous and unbroken sheet over the Rocky Mountain area, nor did they affect all of Alaska or Siberia. Those great glaciers, whose thickness is estimated at from four thousand to ten thousand feet, possessed such tremendous weight and grinding power that they actually remade the face of the country they covered. They moved whole river systems, filled in some lakebeds and scooped out others, wore off the surface of mountains and, in many cases, left plain where hills once stood.

Material from those lost hill and mountaintops was carried hundreds of miles from the point of origin and then re-deposited. The glaciers imprisoned so much water that sea level in warmer parts of the globe was lowered more than two hundred fret, while, because of the resulting cold, the snow line marched down four thousand feet below where it is today. Weight and pressure of the ice caused the earth's surface to crack and buckle so that, when the glaciers finally melted, the parts of the earth they had covered presented an aspect vastly different from their former appearance.

Suppose the glacial age had never happened. There would be no Great Lakes in this country, at least not the lakes in their present form. The eastern mountains would be higher and more rugged. New England would be less stony, and soil of the Middle West might not be so fertile. The Ohio and Missouri rivers would be in considerably different positions, and the entire Mississippi system would be affected. The age of glaciers had a great effect on living creatures, both plant and animal.

By: davidbunch

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