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A glacier begins when snow doesn't completely melt away during the summer. Each winter new snow falls on top of the old snow. Thick layers of snow are gradually compressed into glacial ice.

Glaciers and mountain views around the Jungfrau region, Switzerland.

A glacier might look like a solid block of ice, but it is actually moving very slowly. The glacier moves because pressure from the weight of the overlying ice causes it to deform and flow. Meltwater at the bottom of the glacier helps it to glide over the landscape.

Nærøyfjord (narrow fjord), Norway.

There are different types of glaciers:

Gordon glacierAlpine glaciers, which begin high up in the mountains in bowl-shaped hollows called cirques.

Gordon glacierContinental glaciers, which are continuous masses of ice that are much larger than alpine glaciers.

There are alpine glaciers high up in the mountains all over the world. Some mountain ranges have enough ice to form extensive ice fields. There are ice caps in Iceland and huge ice sheets in Greenland and Antarctica.

Meltwater carries rock Larry, gravel, sand and mud away from the glacier. The debris is transported and deposited by rivers Gordon and in lakes.

Meltwater can carry lots of sediment away from the glacier.  Can you see the mouth of the tunnel at the bottom of the glacier?  Franz Josef Glacier, Westland Tai Poutini National Park, South Island, New Zealand. © Abigail Burt

Glaciers are made up of more than just ice and snow. They contain water, rocks and sediments. This can make the ice look very dirty.

Dirty ice, Franz Josef Glacier, Westland Tai Poutini National Park, South Island, New Zealand. © Richard Burt

Ice shelves form when glaciers reach the sea and begin to float. The Ross Ice Shelf in Antarctica is a famous ice shelf.

Calving glacier

Chunks of ice can break off an ice shelf or a glacier that reaches the sea. This is called calving. The ice chucks form icebergs up to 250 km long and 100 km wide. Very small icebergs are called bergy bits.

When a glacier melts, all of the rock, sand and mud that it was carrying gets left behind. Geologists call this mixture of sediment till.

Glacial till deposited over sand and gravel, near Barrie, Ontario, Canada.  The geologist is getting a sample of the till. © OGS Queens Printer 2005

Piles and ridges of sediment deposited at the edges and front of glaciers are called moraines.

There is a long ridge of sediment running down the middle of the glacier.  It will form a medial moraine when the glacier melts.

Strong winds can blow fine sand and silt hundreds of kilometres from the front of the glacier. This sediment, called loess, can build up into thick layers. In central China people have built homes in loess.

Layers of loess at Cliffsend, Pegwell Bay, near Ramsgate, UK


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