The three major glacial depositional landforms are moraines, drumlins and erratics.
- When the glacier reaches its lowest point and melts, it leaves behind a stratified deposition material, consisting of rock debris, clay, sand, gravel etc.
- This layered surface is called till plain or an outwash plain and a downward extension of the deposited clay material is called valley train.
- Esker is a winding ridge of unassorted depositions of rock, gravel, clay etc. running along a glacier in a till plain.
- The eskers resemble the features of an embankment and are often used for making roads.
- If the melting of glacier has been punctuated, it is reflected in a local widening of the esker and here it is called a beaded esker.
- Kame terraces are the broken ridges or unassorted depositions looking like hummocks in a till plain.
- Drumlin is an inverted boat-shaped deposition in a till plain caused by deposition. The erosional counterpart is called a roche moutonne.
- Drumlins are smooth oval shaped ridge-like features composed mainly of glacial till with some masses of gravel and sand.
- The drumlins form due to the dumping of rock debris beneath heavily loaded ice through fissures in the glacier.
- The long axes of drumlins are parallel to the direction of ice movement.
- They may measure up to 1000m in length and 30-35 m or so in height.
- One end of the drumlins facing the glacier called the stoss
- Kettle holes can be formed when the deposited material in a till plain gets depressed locally and forms a basin.
- Moraine is a general term applied to rock fragments, gravel, sand, etc, carried by a glacier.
- Depending on its position, the moraine can be ground, lateral, medial or terminal moraine.
- The material dropped at the end of a valley glacier in the form of a ridge is called the terminal moraine.
- Each time a glacier retreats, a fresh terminal moraine is left at a short distance behind the first one. The material deposited at either of its sides is known as lateral moraine.
- When two glaciers join, their lateral moraines also join near their confluence and are called medial moraines.
- Many Alpine pastures in the Himalayas like the Margs of Kashmir occupy the sites of morainic deposits of old river valleys.
- The excessive load that cannot be carried forward by a glacier is deposited on its own bed or at the base and appears as what is known as ground moraine.
- A nunatak (from Inuit nunataq) is an exposed, often rocky element of a ridge, mountain, or peak not covered with ice or snow within (or at the edge of) an ice field or glacier. They are also called glacial islands.
Glacial Depositional Landforms
Read More : Glacial Erosional Landforms