. The continent we live on. Physical geography; Natural history. A herd of musk ox in full ;sheep-oxen" are true relics of the Ice Age and. though they look lumpish, can out- pace most other animals. squeezed out underneath as taffy would be in a shallow bowl if a large solid weight were placed upon it. Thus an icecap grows in both depth and area and pushes out in all directions. If it comes against a substantial mountain range, it pushes up and over the lower passes or flows around the ob- stacle, scouring its sides with millions of tons of pressure and billion-foot-poun
. The continent we live on. Physical geography; Natural history. A herd of musk ox in full ;sheep-oxen" are true relics of the Ice Age and. though they look lumpish, can out- pace most other animals. squeezed out underneath as taffy would be in a shallow bowl if a large solid weight were placed upon it. Thus an icecap grows in both depth and area and pushes out in all directions. If it comes against a substantial mountain range, it pushes up and over the lower passes or flows around the ob- stacle, scouring its sides with millions of tons of pressure and billion-foot-pound scooping actions. It finally covers the whole land and leaves only the peaks of the tallest mountains sticking out. These are called nunataks. Such are strewn all around the edge of Greenland. But finally its edge reaches some seacoast. If the coast is a rocky barrier with cliffs, the ice, in the form of glaciers or rivers of ice, cascades down these through whatever gaps there are and, on reaching the sea below, becomes water-borne— ice being lighter than water. As a result, the front ends or "tongues" of these break off in great bits by being bent upward, often with thunderous noises like gunfire, and then go drifting away as icebergs. This is called calving. If. on the other hand, the coast is low but wide, the ice front may push slowly out onto it, building up a mountainous and bulbous front, actually thicker at that front than just behind it, so that the whole curls over like a vast wave and huge masses of ice crash to the bare ground ahead of it. Then the ice slowly creeps over these chunks and reabsorbs them. In still other cir- cumstances, where the coastal plain is narrow and only just above sea level and extends out under the water to form a very shallow sea, the vast ice mass may move slowly out from the land—sometimes for hundreds of miles as in the Antarctic— before its buoyancy counteracts its weight and vast slices of it snap off and become wate
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