Glaciers, huge masses of ice and snow that slowly slide down the slopes of mountains,
cover about 11 percent of earth’s land area. Nicknamed “nature’s ploughs,” they carve
out surfaces on every continent except Australia.
Glaciers form wherever snow collects faster than it can melt. A few days after falling,
snowflakes lose their delicate, lace-like form and are compressed into granules that
eventually fuse into huge ice crystals, some as big as soccer balls. In order to become
a glacier, the frozen crystal mass must accumulate to critical thickness - about sixty
feet. It is at that point that the weight of the ice starts an inevitable downward flow.
Some glaciers creep along slowly, while others slide with surprising speed. The rate of
movement is determined by factors like ice temperature, steepness of the underlying
ground, glacial bulk, and the flow of water between the ice and the earth. Movements
are not always predictable, either. In July 1966, Steel Glacier in Canada’s Yukon
Territory suddenly started sliding forward at two feet per hour. Nicknamed the
Galloping Glacier, this river of ice, as large as Manhattan Island, eventually stopped
a year later, but it had traveled more than six miles with no clues for its unusual
behavior.
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