These are types of landforms of highland glaciation and glacial erosion.
Because glacier places the combines the roles of erosion, transportation and deposition throughout its course.
1. Corrie OR Cirque
are the bowl shaped depressions found at the head of glacial valleys For most alpine glaciers, cirques are the areas in the alpine valleys where snow first accumulated and was modified into glacial ice. The glaciers that occupy cirques are called cirque glaciers.
Many cirques contain lakes, which are called cirque lakes. A cirque is also called corrie(Scottish) or cwm (Welsh).
Cirques are common in glaciated mountain areas in the European Alps and Antarctica.
A cirque occurs when snow collects in cracks or depressions at high altitude.
Alternate freezing and thawing enlarges the depression. As the ice flows away, it enlarges the hollow further through plucking.
An arete are narrow serrated rigdes found in glaciated alpine areas.
It is formed when two cirques meet back to back and the two back walls are eroded by plucking until they produce a narrow, knife-edge ridge.
Pyramidal peak is a jagged peak formed when the backwalls of some corries on the sides of a mountain become steep. The peaks are sharpened by frost. example of pyramidal peak is found at the Matterhorn on the Swiss-Italian border.
3. U-shaped Valley
A U-shaped valley is a steep-sided, flat-bottomed, wide valley which contains features formed by both glacial erosion and deposition.
As a glacier over along a former river valley, it changes the shape of the valley by tearing and wearing away the valley sides.
As a result, the glacier changes the shape of the valley from a V to a U. The floor of the valley is deepened and widened while the sides become steeper
4. Hanging Valley
This is a tributary of a U-shaped valley that ends abruptly above the floor of the U-shaped valley and is separated from it by the almost vertical slope.
Hanging valleys develop because of two reasons:
1) larger, more massive glaciers create greater erosion and subsequently a deeper valley, and
2) some valleys have seen more glacier ice pass through them which also results in more erosion and a deeper valley. Many hanging valleys are also the sites of sensational waterfalls. The Lauterbrunnen in Switzerland is a good example of a hanging valley.
You should bear in mind that hanging valleys are not exclusively caused by glaciers.
For example, they occur whenever down-cutting in the main valley of a river is more rapid than in its tributary valley.
They can occur when a valley abruptly terminates in a sea cliff.
5. Rock Basins and Rock Steps
A rock basin is a depression on the floor of a U-shaped valley. It is usually formed when a glacier erodes and excavates the bedrock of its valley in an irregular manner.
Where a tributary valley joins the main valley, the additional weight of ice in the main valley cuts deeper into the valley floor at the point of convergence to form a rock steep.
These are materials, such as stones, clay, and rock debris that have been transported by a glacier and abandoned in specific formations.
For instance, the debris that falls on the sides of a glacier and forms ridges is called lateral moraines.
When two glaciers meet, the two inside lateral moraines unite to form a medial moraine.
All the rock debris, carried along underneath the ice, as well as materials which fall through cracks in the glacier from the ground moraine or end moraine.
Melting normally begins at the front of the glacier, as it begins to melt back, it is said to ‘retreat’.
If the retreat of the glacier is halted, the front will remain stationary. If it does this for a long time, a recessional moraine builds up.
A recessional moraine often blocks a valley exit and thus acts as a dam across a river. In this way, a moraine-dammed lake is formed.
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