Glacial Erosion and Deposition

Erosion Glaciers have the capacity to carry huge rocks and piles of debris over large distances They grind out parallel scratches in the bedrock –Small scratches are called grooves and larger ones are called striations

As valley glaciers erode the land over which they move, they carve out various U-shaped valleys and mountain landforms:

Cirques, Aretes and Horns

Deposition Glacial deposits are unsorted and are not layered Particles carried by a glacier tend to have an angular to round shape and a rough texture

Glacial Sediment - Till Till is the unsorted rock material directly deposited by glacial ice

Glacial Sediment Erratic – a large rock deposited by a glacier

Glacial Sediment - Drumlins Drumlins – canoe shaped hills of unsorted sediments that form as a glacier moves over the land They indicate the direction of glacial movement

Glacial Sediment - Moraines Much of the debris is left behind in ridges called moraines –Terminal moraines mark the farthest advance of a glacier

The picture below depicts a section of eastern Long Island after the continental glaciers retreated to the north. Sea level rose with the return of meltwater to the oceans, to drown hundreds of square miles of outwash plain and to fill Long Island Sound

Glacial Features - Outwash Plains Beyond the terminal moraine, meltwater runs and carries sediments of gravel, sand, silt and clay These are deposited in sorted layers as they are being deposited by running water as a result of the melting glacier (not by the ice directly)

Outwash plain in front of Thompson Glacier, Axel Heiberg Island, Canadian Arctic

Kames are steep-sided, irregularly shaped mounds of sand and gravel that have been formed by glacial deposition. The term is derived from the Scottish word cam or kaim, meaning "crooked and winding" or "steep-sided mound".

When the glacier melts/retreats: Gouges out land that becomes filled with meltwater forming lakes (Finger Lakes) Scoops out shallow basins that fill with water called kettle lakes

Formation of Kettle Lake

Kettle Lakes

Toe of a valley glacier: