Land forms

(Adpated from s-cool.co.uk)

Glacial Landforms

In Britain, glaciers once covered much of the North.

Erosional Features

Arêtes - Two corries which were formed back to back have now eroded backwards to create a narrow ridge.

Corries - Also known as cirques, they are the starting point of a glacier.

LAST ICE AGE - snow accumulated on hills --> ice --> gouged backwards through freeze-thaw and plucking -->large crevasses at the top of the ice (bergschrund's) allowed water to flow into the ice --> froze to more ice.

Bottom the the corries was eroded by abrasion. Where erosion was less at the front of the ice a rock lip was left. as ice flowed over the lip into the valley below, a glacier was formed.

Lakes were formed when the ice melted the corries. the rock lip and moraine acted as a natural dam. These lakes are called Tarns.

Glacial Trough - The other name for a U-shaped valley cut by a glacier.

Pyramidal Peaks - Formed the same as an Arête but with three corries. Eventually erosion leaves a sharp pyramid peak e.g. the Matterhorn in the Alps.

U-shaped Valley -  Usually a glacier will follow the general direction of a river valley,but cuts through hard rock. This leaves behind a valley with steep sides. 

Rivers that were in the main valley which have been cut by glacial valleys flow over waterfalls from hanging valleys. the spurs have also been cut through to leave truncated spurs behind. a ribbon lake may form on the valley floor with a terminal or recessional moraine to hold the water in.

Depositional Features

Boulder Clay/Till - Material deposited as the glacier melts. Angular stones as they have not been rounded by the water actions (ground moraine). 

Drumlins - Deposited smooth material formed parallel to the direction of the glacier. Formed by moraine being deposited due to obstruction causing more friction for the glacier. Most material is deposited at one end of the drumlin. Ice which flows over it gives it its shape. 

Erratics - These are large boulders that have been carried and deposited by the glacier in an area of differing rock type, so that they look completely out of place. 

Moraines -  Moraine is the term used for any material carried or deposited by a glacier. The five main types of moraine are:

• Terminal Moraine: This is the material deposited at the snout of the glacier at the furthest extent of its growth. May act as a dam for a ribbon lake.

• Lateral Moraine: Runs parallel to the glacier and is the material that has been eroded from the valley sides by the actions of freeze-thaw and the glacier itself. Once the glacier melts this will be left on the valley floor.

• Medial Moraine: Where two glaciers meet, their lateral moraines meet to form a medial moraine, which runs down the centre of the glacial surface. Once the glacier melts this will be left on the valley floor.

• Ground Moraine: otherwise known as boulder clay or glacial till, this is the material deposited on the valley floor by the glacier. It is usually the result of plucking and abrasion.

• Recessional Moraine: Similar to a terminal moraine they were created when the glacier retreated and then stopped, allowing it to build up a pile of deposits. A recessional moraine could act as a dam to create a ribbon lake.