SP

Landforms of Highland Glaciation

This are types of landforms of highland glaciation and glacial erosion. Because glacier place the combines the roles of erosion, transportation and deposition throughout its course.

1. Corrie, Cirque or Cwm: This is a highland glaciation landform which is a semi-circular or an armchair-shaped hollow, usually found at the upper end or sides of a glacial valley. 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 Antartica.

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.

2. Arete and Pyramidal Peaks: An arete is a jagged, steep-sided mountain ridge common in the European Alps. It is formed when two corries meet back to back and the two backwalls 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 which ends abruptly above the floor of the U-shaped valley and is separated from it by almost vertical slope. The main valley of a glacier erodes more quickly than the tributary valleys. After the ice has melted, a tributary valley hangs above the main valley. If the hanging valley contains water, it descends to the main valley as a waterfall. The Lauterbrunnen in Switzerland is a good example of a hanging valley. You should bear in mind that hanging valleys are notexclusively 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. Some hanging valleys are also produced by faulting. Hanging valleys can form a natural head of water for generating hydro-electric power.

4. 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 a 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.

6. Moraines: 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.