This edited article about glaciers originally appeared in Look and Learn issue number 694 published on 3 May 1975.
For thousands of years the river of solid ice has been creeping down the mountainside, slowly and relentlessly grinding and cutting a valley between the mountain peaks capped with their eternal snow.
This moving river of ice is called a glacier, from the Latin-French word glacis meaning ice.
How are frozen rivers such as this one formed? When snow falls on high mountains, one of two things can happen.
The sun may melt the snow so that it flows down the mountain as a river of water.
But if the mountain top is very cold the snow hardens and slides down into a valley. If the valley is also very cold the snow collects there and is squeezed and frozen into the river of ice we call a glacier.
Pushed forward by the ice forming behind it, the glacier moves slowly down the valley, scratching and grinding the rocks over which it passes and in time digging out for itself a deep channel.
During its formation and while it is travelling down the mountain, a glacier collects large pieces of rock which become frozen into it and stick out like teeth from the bottom of the ice. While the immense weight of ice is moving, these teeth cut great grooves in the ground over which the ice is passing.
A lot of glaciers end their lives in warmer valleys where their ice melts and becomes a stream or small river.
You will find them where there are high mountains and a cold climate. Antarctica, Iceland, Greenland, Norway, the Himalayas and Switzerland are the great breeding grounds of glaciers.
In Switzerland, where there are over two thousand of them, glaciers are quite short, seldom more than four miles long. But in Antarctica they are hundreds of miles long and sixty miles wide.
In very cold parts of the world, particularly in Antarctica and the far north of the American continent, glaciers move down to the sea. There huge pieces of the frozen rivers break off and float away as icebergs.
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