Landscapes created by Glacial erosion Flashcards
What are the two types of landscape formed by glaciation
- Features formed by Erosion
- Features formed by Deposition
How does a corrie develop
A corrie is often the starting point for a glacier
Snow falls and collects in a hollow often on the north face of mountain or hill, where the rate of accumulation is higher than the rate of ablation.
This repeated snow fall compresses into firn or neve and then eventually glacial ice.
Although the ice is trapped gravity will cause it to move in a circular fashion (Rotational Slip) This movement creates a steep rear wall owing to plucking and freeze thaw weathering and a deep hollow by the process of plucking, abrasion and freeze thaw weathering
As the ice breaks away from the rear wall of the corrie a bergschruind crevasse can form
The rate of erosion at the front of the corrie experiences less erosion and debris is often deposited here. This forms a characteristic armchair appearance.
When the ice melts a lake forms and is called a tarn e.g. Red Tar, Helvellyn
What is an arete and how does it develop
An arete is a sharp ridge develops when two corries either side of a Mountain cut back to back
Each corrie develops a steep rear wall owing to plucking and freeze thaw weathering, giving rise to the charateristic steep ridge
e.g. Striding edge, the Lake district
What is a pyramidal peak
When 3 aretes come together a pyramidal peak is formed e.g. The Matterhorn
What is a glacial trough and how does it form?
Glacial Trough is a u shaped valley
As a glacier travels down a river valley it leaves a u shape valley owing to the processes of glacial erosion i.e. pucking, abrasion and bulldozing and freeze thaw weathering.
What is a truncated spur
River valleys can have ‘Interlocking spurs’ like the teeth in a zip that overlap.
When a glacier flows through the valley, the glacier cuts into these spurs leaving a truncated spur and a straight u shaped valley
What is a hanging valley and how does it form
A hanging valley is formed when a large glacier is joined by a small tributary glacier (1)
The large glacier mover down a v-shaped valley and through the processes of plucking and abrasion deepens the valley floor and straightens the valley sides, leaving a large U-shaped valley (1).
The same processes of plucking and abrasion take place in the tributary glacier, but at a much slower rate (1).
This is because the large glacier is far heavier and more powerful, and therefore can erode the land more quickly (1).
This different rate of erosion means that the small tributary glacier does not erode anywhere close to the depth of the large glacier.
When the ice melts a large U-shaped valley is left where the large glacier had been. The smaller glacier leaves a small valley leading into this and “hanging” from the truncated spurs. (1)
There is often a waterfall left coming from the hanging valley (1).
What is a ribbon lake and how is it formed
A ribbon lake is formed in the base of a U shaped valley
As a glacier advances over hard and soft rock, the erosion of soft rock by plucking and abrasion is higher than the hard rock
When the glacier retreats, the hollow left in the soft rick is deeper than the hard rock.
The ice melts and fills this hollow e.g. Lake Windemere
A ribbon lake could also form when a glacier retreats and the water is trapped in an area by the terminal Moraine left when the glacier retreats.
How do glaciers transport rock
As the glacier moves it plucks the rock out of the landscape and freezes it in the base of the glacier.
As the glacier moves this rock carves through the landscape by abrasion.
