Grade IX Geography : All About Glaciers

A glacier is a huge mass of ice that moves slowly over land. The term “glacier” comes from the French word glace (glah-SAY), which means ice. Glaciers are often called “rivers of ice.”  Glaciers fall into two groups: alpine glaciers and ice sheets. The image here is an alpine glacier.

In glacial erosion, in addition to abrasion (q.v.) which leaves striations, gouge marks, etc., a peculiar pulling away process is called glacial plucking or quarrying, because it involves the dislodging and removal of large fragments and boulders.

Abrasion occurs when rocks and stones become embedded in the base and sides of the glacier. These are then rubbed against the bedrock (at the bottom of the glacier) and rock faces (at the sides of the glacier) as the glacier moves. This causes the wearing away of the landscape as the glacier behaves like sandpaper.

As ice flows downhill, it either reaches warmer climates, or it reaches the ocean. This causes various processes of melt, or ablation, to occur.

A moraine is material left behind by a moving glacier. This material is usually soil and rock. Just as rivers carry along all sorts of debris and silt that eventually builds up to form deltas, glaciers transport all sorts of dirt and boulders that build up to form moraines

Meltwater is water released by the melting of snow or ice, including glacial ice, tabular icebergs and ice shelves over oceans.

Ice calving, also known as glacier calving or iceberg calving, is the breaking of ice chunks from the edge of a glacier. It is a form of ice ablation or ice disruption. It is the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse. 

Glaciers cause erosion by plucking and abrasion. Valley glaciers form several unique features through erosion, including cirques, arêtes, and horns. Glaciers deposit their sediment when they melt. Landforms deposited by glaciers include drumlins, kettle lakes, and eskers.

A drumlin, is an elongated hill in the shape of an inverted spoon or half-buried egg formed by glacial ice acting on underlying unconsolidated till or ground moraine. 

Kettles are depressions left behind after partially-buried ice blocks melt. Many are filled with water, and are then called "kettle lakes".

Eskers are formed within ice-walled tunnels by streams that flowed within and under glaciers. They tended to form around the time of the glacial maximum, when the glacier was slow and sluggish. After the retaining ice walls melted away, stream deposits remained as long winding ridges.