At the bottom of the world lies a mighty continent still wrapped in the Ice Age and, until recent times, unknown to man. It is a great land mass crisscrossed (交叉往来) by mountain ranges whose (62) and height are still uncertain. Much of the continent is a complete blank on our maps. A 1 000-mile (63) of the coastline has never been () by any ship. Man has (65) , on foot, less than one percent of its area. Antarctica differs slightly (66) the Arctic regions. The Arctic is an ocean, covered with (67) packed ice and surrounded by the land masses of Europe, Asia, and North America. The Antarctic is a continent (68) as large as Europe and Australia (69) , centered roughly on the South Pole and surrounded by the most (70) water areas of the world—the Atlantic, Pacific and Indian Ocean. The continental ice pack is more than two (71) high at its center; thus, the air over the Antarctic is far more refrigerated (冰冻的) than it is over the Arctic regions. This cold air falls (72) the land with such force that it (73) the nearby seas the stormiest in the world and renders (74) those regions whose (75) at the opposite end of the globe are inhabited. (76) , more than a million persons live (77) 2 000 miles of the North Pole in an area that (78) most of Alaska, Siberia, and Scandinavia—a (79) rich in forest and mining industries. Except for a handful of (80) stations, within the same distance of the South Pole there is not a(an) (81) tree, industry, or settlement.