Glacial Landscapes

Question 1

What is a glacier?

Answer 1

Glaciers are large, slow moving rivers of ice

Giant glaciers are called ice sheets

Glacial ice is formed from layer upon layer of falling snow every year

It takes 20 to 30 years for the layers to compress and form glacial ice

Glaciers will grow in size if the temperature stays below 0°C

Glaciers shape our landscape

Question 2

Glacial Erosion

Answer 2

Plucking:

• As a glacier moves through a valley, pressure is exerted on the sides and bottom of the valley
• This generates friction and heat, causing the edges of the glacier to melt a bit
• This meltwater freezes around rocks and stones under the glacier
• As the glacier moves forward, it ‘plucks’ this ice, pulling the rock away
  Abrasion:
• Abrasion occurs as bits of rocks, stones and boulders stuck in the ice, grind against the rock below the glacier wearing it way
• **Rotational slip is the circular motion of the ice in a hollow **

Question 3

Glacial Landforms

Answer 3

Moraines
Unsorted glacial till that is deposited in mounds are called moraines

There are four types of moraines:

Terminal: Material deposited at the snout of the glacier

Lateral: Material is deposited along both sides of the glacier

Medial: Ridge of deposited material in the middle where two glaciers meet and continue to flow downhill together

Ground: Material dragged under the base of the glacier and deposited over a wide area on the valley floor
Drumlins
Drumlins are elongated, egg-shaped hills and made of glacial till

They form beneath the glacier when the glacier meets an obstruction and material is deposited as a ground moraine

The moraine is then shaped by the moving ice, which follows the direction of the flow of ice

The largest ones can be over 1km in length, 0.5km wide and 50m high

Multiple drumlins are known as swarms or baskets of eggs

As the material is deposited it builds up to have a round, blunt and steep front (stoss) end

The flow of ice over the top of the drumlin, drags the material along and down creating the lee slope

The lee is gently sloped, elongated and with a tapered tail
Pyramidal peak

As the name suggests, this is a three-sided, pointed mountain peak

Formed when three or more back-to-back glaciers carve away at the top of a mountain

This creates a sharply pointed mountain summit
Arête

Arêtes are knife-edge, steep-sided ridges

Formed when two glaciers flow back-to-back

As each glacier erode either side of the ridge, the edges become steeper and the ridge narrower

This gives the arête it’s a jagged profile

Corrie/cwm/cirque

Corrie, cwm and cirques are all the same feature and are formed in hollows where snow can accumulate, usually on a north facing slope

In Wales corries are called cwms and in France they are called cirques

Formed when the glacial ice moves through gravity, rotational slip, and sheer mass of the ice

Ice freezes on the back wall of the hollow and as the ice moves, it plucks the rock out, which steepens the back wall

Tarn

Tarn lake or corrie loch is a mountain pool or lake in a corrie after the glacier has melted

Because of the corrie lip at the bottom end, the meltwater is held in place and a circular body of water is formed