A glacier is a large body of ice and snow. It forms because the snow in an area does not all melt in summer. Each winter, more snow is added. The weight of all the snow creates pressure. This pressure turns the lower parts of the snow into ice. After this happens for many years, the glacier will start growing large. It becomes so heavy that gravity causes the ice to move. It flows downwards like water but very slowly. A glacier only moves about 50 meters (160 ft) per year. New snowfalls replace the parts that flow away.
Glaciers are the largest sources of fresh water on Earth. The largest bodies of salt water are the oceans.
Glaciers will only form in places that are cold enough and get enough snow over time. This can take a long time. It often takes tens or hundreds of years for a glacier to form. There are two kinds of glaciers: continental glaciers and alpine glaciers. Alpine glaciers are also called mountain glaciers.
- Continental glaciers are glaciers that spread out over a large area of land. The broken parts that float in the sea are called icebergs.
- Alpine glaciers form in mountain areas. Alpine glaciers usually flow until they reach a point where the temperature is warm enough that the ice melts completely during the summer.
Glaciers can look blue because they are made of water. The thicker the glacier is, the more blue it appears because more blue light is being absorbed.
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