GLACIATION

Glaciers are formed when ice accumulation is greater than ablation.
Over vast areas in the higher latitudes, slowly moving currents of ice scraped away all the soil and much of the weathered mantle that formerly covered the land.
Elsewhere, the melting of enormous masses of debris-laden ice completely submerged the previous landscape under a blanket of boulders, gravel, sand, silt and clay. This created rolling or flat plains where once there were hills and valleys produced by fluvial erosion.
As the ice retreated (melted), most of the glacial landforms seen across Canada were created. There were minor re-advances during the overall retreat, but in general, the retreat was relatively rapid, with ice withdrawn from most of Canada by 10 000 years B.P.
Landforms resulting from continental glaciation: Drumlins, till plains, moraines, erratics, eskers, spillways, meltwater channels, kettle lakes, and kames.

TILL - Any type of sediment which has been picked up and carried by glacial ice.

TILL PLAIN - A wide area of low relief created by a covering of till which masks all irregularities in the underlying rock. The glacial deposits vary in thickness, being greatest over the bedrock hollows and thinnest over ridges and hills.

DRUMLIN - A streamlined, elongated hummock or hillock of glacial drift, consisting generally of glacial till. A drumlin is teardrop - shaped, with its long axis parallel to the direction followed by the retreating ice sheet. Formation occurs during ice movement over a pre-existing landscape of ground moraine. Drumlins usually occur in groups called a field, or a swarm, and are popularly termed "a basket of eggs" because each drumlin is shaped like half an egg.

MORAINE - An accumulation of heterogeneous rubbly material, including angular blocks of rock, boulders, pebbles, and clay that has been transported and deposited by a glacier or ice sheet.

SPILLWAY - A channel, often streamless, cut in solid rock or in drift, having been carved out by the overflow of an ice-dammed lake.

MELTWATER CHANNEL - A channel cut into solid rock or drift, that created a pathway for the huge volumes of meltwater coming off the glacier during its retreat. It is unrelated to the present drainage system, and it is often associated with kame terraces or eskers.

ESKER - A narrow, sinuous ridge of partly stratified coarse sand and gravel of glacio-fluvial origin. Eskers wind across the countryside, and frequently bear no relationship to the modern drainage pattern. They were formed by rivers of glacial meltwater flowing under the ice in tunnels, at great velocities, and under great pressures.

ERRATIC - A large fragment that has been transported by moving ice, away from its place of origin and deposited in an area of dissimilar rock types. ie, a piece of Canadian Shield found in Southern Ontario.

KAME - glacio-fluvial deposits forming a steep-sided ridge or cone-shaped hill.

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