Question.
Glacial valleys show up many linear depositional forms. Give their locations and names. ( NCERT, Class 11, Fundamentals of Physical geography)
Answer.
Due to the weight of the glacier and the friction generated by its motion, glaciers cause great erosion of the land. The eroded materials are carried by glaciers from the slopes of mountains to glacial valleys. Deposits of these eroded materials form many linear depositional landforms.
The following are the linear deposition landforms in the glacial valley:
- Moraines
- Eskers
- Drumline
- Outwash Plain
Moraines:
The long ridge of glacial till[unsorted sediments] is called Moraines. There are three types of moraines according to the location in the glacier valley:
Terminal moraines:
- A long chain of parallel deposits till on both sides of a glacial valley is called terminal moraines.
Lateral moraines:
- Horseshoe or crescent-shaped long deposit which is formed in the middle of the valley and is attached to the terminal moraines is called lateral moraines.
Ground Moraines:
- Irregular shapes of long ridges that accumulate in a glacial valley are called Ground Moraines.
Eskers:
- The long curved deposits in the glacial valleys are called eskers. Esker is formed by the deposition of eroded material beneath a glacier by the flow of a glacial stream. It is visible only after the glacier has melted.
Drumlins:
- When glacial deposits form an oval shape on glacial valleys, it is called a drumlin. Drumlins can be up to 1 km in length and 30 meters in height.
Outwash plains:
- When gravel, sand, silt, and fine clay, and small eroded material are deposited in a more systematic manner by glacial stream [after thawing] and form an extensive flat alluvial plain, it is called Outwash plains.
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