Glacial ice is made of frozen fresh water (not salt water); glaciers contain the largest reservoir of fresh water on Earth. Glaciers contain about 75% of the fresh water on earth and cover about 10% of the land. During the last Ice Age (which ended about 10,000 years ago), glaciers covered almost a third of the land.
The word glacier comes from the Latin word for ice, "glacies." The study of glaciers is called glaciology; a scientist who studies glaciers is called a glaciologist.
Where Glaciers Are Located
Glaciers are located in cold areas that get snow in the winter and have relatively cool summers. Most glaciers are located near the North and South Poles or are high in the mountains. Glaciers can be found on every continent on Earth except Australia (but there are glaciers on other islands of Oceania). Glaciers are also found on some other planets, including dry-ice glaciers on Mars.
How Glaciers Form and Shrink
Glaciers form when snow falls and accumulates in cold areas in which the snow does not all melt in the summer. A glacier will grow in mass when winter snowfall is greater than summer snowmelt. A glacier will shrink in mass when winter snowfall is less than summer snowmelt.
As snow accumulates in a glacier it becomes heavier, and the snow is compressed under the pressure, turning into ice. The top of a glacier is snow, but deeper layers are made of snow that has been compressed into ice. The bottom of a glacier is a thin layer of water (from glacial melting or from water that seeps through cracks in the glacier).
The mass of glacial ice combined with the slope of the Earth under it cause the ice to inch its way downwards or outwards, sliding on the thin layer of water. Mountain glaciers flow downhill and continental glaciers flow outwards. As a moving mass of ice and snow, the ice mass is classified as a glacier.
When one parts of a glacier moves more rapidly than other parts, that area becomes relatively unstable, and deep cracks or chasms (called crevasses) form in the ice.
Compressed glacial ice looks bluish in color (glacial ice that looks white is full of bubbles).
Types of Glaciers
Two of the main types of glaciers are ice sheets (also called continental glaciers) and Alpine glaciers (also called mountain glaciers).
Ice sheets are huge masses of glacial ice and snow that cover large areas of land; they are dome-shaped. Ice sheets cover much of Antarctica and Greenland.
Alpine glaciers are glaciers that form on mountains; these high-altitude glaciers exist all over the world...
Инициатор: группа В-3(1). Кабинет №2.