Glacier

gla'sher, a stream of slow-moving ice. The typical glacier is formed on a mountain plateau above the snow line by the accumulation of snow. The under layers are pressed into ice and begin a slow journey down the valleys. The rate of movement depends on the size of the glacier and the slope of the land. Glaciers move faster at their centers than at their sides, and faster in warm weather than in cold. A rate as slow as an inch or two a day is nothing unusual. The swiftest parts of the Alpine glaciers move from one to three feet per day. The central part of the Muir glacier in the northern Rockies, it is stated on the authority of the explorer for whom this glacier was named, advances at the rate of ten feet per day. In turning a corner or falling over a slight brow, the ice cracks, forming crevasses differing in thickness from the width of a knife blade to cracks of thirty feet or more. Sometimes these cracks are several miles long and a quarter of a mile deep. They are frequently hidden by a fall of snow, rendering travel on the surface of the glacier extremely perilous. As the ice stream advances these cracks close up and freeze solid under pressure. This statement need not seem strange, for the crevasses are dripping with moisture, and pieces of wet ice freeze together very readily. Two pieces of ice floating in hot water will unite if pressed together. As the stream of ice pours slowly along it tears off stones, soil, and rocks, sometimes as large as a house, and carries them down the valley. Such a streak of litter is called a moraine. When at the side of a glacier, it is a lateral moraine. When glaciers come together, their uniting edges form a central moraine. The debris deposited at the lower end of the glacier, where the ice melts away, is called a terminal moraine. A terminal moraine in some respects resembles a delta, except that the material composing it is usually very coarse.

The greatest glacier in the world is an enormous field of ice or an ice cap, covering apparently the entire Antarctic continent. Whichever way explorers attempt to reach the south pole, they come upon this field of ice, from the edges of which icebergs, sometimes several miles in diameter, are breaking off into the Antarctic ocean. The north pole is supposed to be situated in an open sea, but a second field of ice covers Greenland with the exception of a single rocky mountain in the interior and a few slender strips of land near the coast. This Greenland ice is the source of the icebergs that drift southward into the path of steamers and render North Atlantic navigation so perilous. Australia has no glaciers; Africa has none, save those descending from two mountains situated, singularly enough, near the equator. The best known glaciers are those of the Alps. They have been studied by many eminent scientists, including John Tyndall, whose Hours of Exercise in the Alps is still authority on the subject. There are over 1,000 Alpine glaciers. The largest are from ten to fifteen miles in length. The Rhone glacier, from whose icy front the infant Rhone emerges, is one of the most noted, and is easily accessible. Other European glaciers are found in the Pyrenees, the Caucasus, and especially the mountains of Norway. New Zealand has a number of fine glaciers almost reaching the sea. The Ganges and other Asiatic rivers take their rise in the lofty glaciers of the Himalayas. In South America glaciers are found throughout almost the entire extent of the Andes. Some of the grandest glaciers of the world are to be found in North America. There are about sixty-five short glaciers in California. There are a number from five to ten miles long in Oregon and Washington, and there are large glaciers along the western coast of British Columbia and Alaska.

One of the most noted is the Muir glacier. It is at least fifty miles in length and twenty-five miles wide. It approaches the sea with a front of twenty-two miles, over two miles of which actually reach into the water, forming a high wall about 300 feet of sheer perpendicular. This glacier may be approached by tourist steamers with perfect safety, and is one of the well known sights of the Pacific coast. Occasionally enormous icebergs break off; but in general the Muir is very well behaved. A large part of the earth's surface has been covered at one time or another with moving ice sheets. Wherever loose, well worn boulders and gravel lie on hills, as well as in valleys, it is pretty safe to assert that they have been carried thither by a glacier which, as it thawed away, left its burden of rocks and earth where we find them. Warren Upham, an authority on the subject, states that 4,000,000 square miles of North America are covered with soil laid down by glaciers.