Glaciers are rivers of ice moving at a very slow speed. They are confined to high altitudes and high latitudes as the temperature is much below the freezing point. There is a permanent cover of snow and ice, as more snow falls here than melts. The line beyond which the snow never melts is called the snow line. In the equatorial regions it is at a height of 5,500 metres, in the Himalayas it is at 4250 metres and in the polar regions it is at sea-level.
The glaciers are of two types – (a) the continental glaciers and (b) the mountain glaciers.
As the glacier moves down the slope it scoops the rocks at the valley head forming an arm-chair shaped basin known as the Cirque. While the glacier moves, it broadens and deepens its valley. It has a broad flat floor and steep sides (U shaped valley).
When the glacier melts it deposits the rock fragments, big and small, on its side and on its bed. These deposits of the glacier are known as moraines.