Glacial landforms, their characteristics and their formation

As a glacier moves down a valley, it carves out a number of distinctive landforms:

• Corries
• Pyramidal Peaks
• Aretes
• Truncated Spurs
• Hanging Valleys
• Ribbon Lakes
• U-Shaped Valleys
• Moraine
• Erratics
• Drumlins

Corries:

When an ice age occurs on north facing slopes, winter snow builds up in hollows on the sides of the mountains and summits. The snow will slowly develop into ice, above and around the hollow, freeze thaw will occur and will shatter the rock.

The rocks will fall and be carried away as the accumulated ice overflows from the hollow, and moves off downhill into the valley.

The backwall of the not yet completely formed corrie, becomes steeper, and rugged (caused by plucking)

This also means the hollow will be cut back in towards the summit. The moving ice uses the plucked material, and weathered rocks to grind out and deepen the base of the hollow. (Abrasion).

It forms an armchair shape with sharp edges. A lip develops for erosion is less because the ice tends to slip from underneath as it moves.

When temperatures begin to increase, ablation rate increases and the ice retreats and disappears. The base of the cirque will contain a lake as the ice melts and post-glacial precipitation occurs. These lakes are known as tarns.

Screes develop around the sides and back of the corrie. The screes are a result of freeze thaw during winter months or material simply falling off the mountain sides as there is no longer any ice to support it. This is called pressure release.

Pyramidal Peaks

Snow accumulates in a hollow on the north slope of a mountain. Snow compacts to form a glacier, and starts to flow down the valley. Plucking and abrasion deepens the hollow. The deep back wall is also weakened, this forms a corrie. The corrie then retreats back into the mountain.

If corries form on at least 3 sides of a mountain, the top of the mountain will become a sharp peak of jagged rock, known as a pyramidal peak. This is continually sharpened by frost action and plucking.

Pyramidal peaks have a steep summit, steep jagged sides, shaped like a pyramid, also known as a horn. E.g. the Mattahorn.

Aretes

Snow accumulates in a hollow on the north slope of a mountain. Snow compacts to form a glacier, and starts to flow down the valley. Plucking and abrasion deepens the hollow. The deep back wall is also weakened, this forms a corrie. The corrie then retreats back into the mountain.

When one or two corries form next to each other on a mountain side, the sides are steep and rocky. The piece of land between them is a ridge called and Arete. It is continually attacked by freeze thaw weathering and plucking.

Aretes are sharp knife edged ridges on the side of mountains. They have steep sides which form the back walls of corries. They contain jagged bare rocks, with no vegetation.

Truncated Spurs

A glacier forms at the head of a river…