Glaciers

Glaciers

A glacier is a river of ice.
It moves very slowly.
Glaciers are in places where the snow never melts.
Bits of glacier break off and fall in the sea.
Then they are called icebergs.

Glaciers are rivers of ice. They form in places where snow falls but never melts. Most glaciers are found near the Poles, but all continents except Australia have glaciers. There are glaciers on New Zealand and Papua New Guinea, countries in the region of Australia.

Photograph © [2007] Jupiterimages Corporation

How glaciers form
Layers of snow build up because they don’t melt. The layers turn to ice, and a mountain of ice forms. The heaviness of the upper layers of snow presses down on the lower layers. This compression causes the ice crystals in the under layers to become bigger and the air spaces around them smaller, which is the reason a thick glacier looks blue in colour.

The combination of gravity and the weight of the mountain makes it begin to move downwards and outwards. As the glacier moves slowly down the mountain, it grinds against the ground and the walls of its path to make it deep and wide. The valley of a river is V-shaped, but a glacier’s valley is U-shaped, wide and flat on the bottom.

Glaciers move very slowly, but when they move faster, the stress inside makes deep cracks, called crevasses, to form.

Glacier types
There are two main types of glacier: valley glaciers and ice sheets.

A valley glacier is a mountain of ice that flows between the walls of its valley.

An ice sheet is a dome-shaped mass of ice that flows from a central point outwards to cover a large surrounding area, and is bigger than 50,000 square kilometres.

Glaciers change their environment
Glaciers have an enormous effect on their environment by erosion and depositing. As they move, they erode the earth and form a deep valley. They wear away the soil by picking up and moving rocks and stones as they move, and depositing them at the sides or carry them along and deposit them where the glacier ends.

End of a glacier
Eventually, glacier ice reaches a point where it melts and evaporates but if a glacier reaches a large area of water such as a lake or the sea, big sections of glacier break off and fall into the water.

Those huge pieces are then called icebergs, and the process of breaking away from the glacier is called ‘calving’.

Go here for more information about glaciers
http://www.uvm.edu/whale/GlaciersWhatAre.html
http://magma.nationalgeographic.com/ngexplorer/0501/quickflicks/
http://www.genomenewsnetwork.org/articles/2004/06/10/glacierlife.php
http://nsidc.org/glaciers/

If you use any of this in your own work, acknowledge this source in your bibliography like this:
Sydenham, S. & Thomas, R. Glaciers [Online] www.kidcyber.com.au [2008]