Revision:Glacial Deposition

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There are two different types of landforms that result from glaciation. The first group is known as glacial deposits and the second fluvio-glacial deposits. Glacial deposits are unsorted by the glacier while fluvio-glacial deposits have been sorted.

Glacial deposits

Moraines

When glacial ice melts, different types of rock are deposited that have been carried along by the glacier. Piles of these deposits are called moraines. There are several different types of moraine:

• Terminal moraine- Moraine that has been deposited at the furthest extent that the glacier reached before beginning to melt.
• Recessional moraine- Moraine that has been deposited during 'stand-stills' in the glacier retreat.
• Lateral moraine- Moraine that has been transported along the sides of the glacier and later deposited along the sides of a valley.
• Medial moraine- When two glaciers join together, the lateral moraines at the sides which the glaciers joins are pushed into centre of the new larger glacier.
• Ground moraine- Moraine that is transported underneath the glacier and deposited as the glacier starts to lose the force to carry it. Also called boulder clay or till.

Erratics and Drumlins

Erratics are rocks and boulders picked up and transported many kilometres by the glacier. They are later deposited in an area with a different rock type. Rocks from Norway have been found in coastal cliffs in East Anglia in England.

Drumlins are elongated hills of glacial deposits. They can 1 kilometre long and 500 metres wide. Drumlins are often found in groups and these groups are called drumlin swarms and can be described as a basket of eggs. The long axis of the drumlin shows the direction that the glacier was moving in. When the glacier become overloaded with rock debris, it would have deposited the drumlins. The steep side of the drumlin was where the glacier first deposited then shaped the drumlin. Glaciologists still disagree about the exact details on how drumlins were formed.