Glacial Landforms Flashcards
what are the different landforms caused by erosion
- corries
- aretes and pyramidal peaks
- troughs
- roche moutonnes and striations
- ellipsoidal basins
how are corries formed
- Snow collects in a sheltered hollow on the side of a mountain. This is usually on North-facing slopes in the northern hemisphere. The snow doesn’t melt in the summer because it is high up, sheltered and cold.
- Every winter, more snow collects in the hollow. This becomes compacted and the air is squeezed out leaving ice.
- The back wall of the corrie gets steeper due to freeze-thaw weathering and plucking
4.The base of the corrie becomes deeper due to abrasion
5.As the glacier gets heavier it moves downhill. The glacier moves out of the hollow in a circular motion called
rotational slip
6.Due to less erosion at the front of the glacier a corrie lip is formed.
7.After the glacier has melted a lake forms in the hollow. This is called a corrie lake or tarn.
what is a corrie
- arm chair shaped hollow found in upland hills or mountain sides. They have a steep back wall an over deepened basin and often have a lip at the front which may be solid rock or made of morinic deposits
whats an arête
is a narrow, steep sided rifle found between two corries. this ridge is often so narrow that it is described as knife edged
how’s an arête formed
It is formed when two corries run back to back. As each glacier erodes either side of the ridge, the edge becomes steeper and the ridge becomes narrower.
hows a pyramidal peak formed
A pyramidal peak is formed where three or more corries and arêtes meet
whats a trough (U shaped valley)
long U shaped valleys that were carved out by glaciers that have since receded or disappeared. Troughs tend to have flat Valley floors and steep straight sides
how is a trough formed
glaciers flow down pre existing river valleys under gravity. As they move the erode the sides and floor of the valley, causing the shape to become deeper, wider and straighter.
what are Roche moutnonees
a mass of resistant rock which has a smooth, rounded up valley (STOSS) slope facing direction of ice flow and down (LEE) slope by plucking. as the glacier encounters the obstacle pressure increases and allows melting to occur. this allows the ice to melt and basal sliding to occur, can leave strations.on the LEE side pressure falls and the water refreezes and as the ice moves downhill it pulls away masses of rock; plucking the rocks underneath, this leaves a steeper sided note jagged see slope.
what are striations
when ice passes over over the valley the valley is smooth and streamlined by abrasion and often has striations which are scratches or groves made by debris embedded in the base of a glacier
what are ellipsoidal basins
deep, elongated lakes, formed by subglacial activity beneath past ice sheets
major erosional landforms created by ice sheets. the Laurentide ice sheet covered much of North America between 95,000 and 12,000 years ago. erosion by the Laurentide ice sheet produed a series of ellipsoidal basins in North America.
