Ice

Valley Floor3. Rocks scrape along the

valley floor and erode it.

2. Glacier moves

This type of erosion is called abrasion.

1. Rocks frozen into glacier ice.

Glacial Erosion

Glacial Erosion

Ice

Rock

1. Ice freezes around bits of rock1. Ice freezes around bits of rock

2. The Glacier moves

3. Bits of rock are taken from the rock face with the ice

This type of erosion is called plucking

Formation of a Corrie

• Mention what the shape was like before

• Mention what the shape is like afterwards

• Mention how the shape was changed

How to answer the question:

‘Explain how a corrie was formed.’

Before Glaciation

• Snow falls in a hollow high in the mountains

• The snow compresses into ice

During Glaciation• The ice moves downhill

as a glacier

A

B

C

For full credit marks mention how abrasion, plucking & freeze thaw work

•At ‘A’ freeze thaw weathering makes the backwall steeper and jagged

•At ‘C’ abrasion deepens and smoothes the hollow

•At ‘B’ plucking makes the backwall steeper and jagged

After Glaciation

• The corrie has steep sides and steep back wall

• The hollow is deeper

The lip is The lip is emphasiseemphasised by d by moraine moraine deposited deposited by the by the glacierglacier

Often Often water fills water fills the corrie the corrie known as a known as a tarntarn

1. Two Glaciers erode back to back into a mountain by plucking as they move downhill.

2. This forms 2 corries.

3. Plucking makes the ridge narrower and this is called an Arete.

4. Freeze-thaw weathering makes the Arete sharper

1. Where glaciers start in a hollow they move downhill and erode by plucking and abrasion to form corries.

2. Three or more corries form back to back or side by side

3. Where the corrie sidewalls meet they form ridges which become narrower by plucking.

4. These are called Aretes. Three Arêtes meet to form a pyramidal peak

5. The peak becomes sharper by freeze-thaw weathering

Formation of U-shaped valleyBefore glaciation a v-shaped valleyDuring the ice age a glacier moves down the valley.

Rocks trapped in the bottom of the ice act like sandpaper wearing away the valley by abrasion.

The glacier deepens, straightens and widens the valley by abrasion.

After the ice melts a U-Shaped valley remainsAfter Glaciation there is sometimes a mis-fit stream or ribbon lake in the bottom of the valley

1. Erosion in the main glacier is far greater making a deeper valley.

2. Erosion in the tributary glaciers is less making a shallower valley.

3. The shallower valleys are left ‘hanging’ above the deeper main valley.

4. Waterfalls often fall over the edge at the end of the hanging valley into the main valley.

5. At the base of a waterfall alluvial fans are sometimes found as a result of deposition

Map View

Main valley

Tributary valley

Cross Section

Main valleyTributary

valley

Ribbon Lakes1. Glaciers move down a former v-shaped valley

and erode the valley by abrasion and plucking turning the valley into a u-shape.

2. Some ribbon lakes form when the glacier meets softer rock.

3. The glacier erodes more deeply at these points. 4. After the glacier has melted the deeper parts fill

with water to form ribbon lakes

Side view of valley before Glaciation

Side view of valley after Glaciation

Hard Rock Soft Rock

Hard Rock

Hard Rock

Hard RockSoft Rock

Ribbon Lake

How Till is formed1. The temperature rises due to climate change at the end of

the ice age or the temperature rises as the glacier reaches lower land.

2. The glacier begins to melt. The snout moves back up the valley.

3. The melting ice cannot hold the rocks, gravel and sand that have been trapped in it.

4. All this material is deposited as the glacier continues to melt. 5. The moraine is all mixed up with different sizes of material. 6. Where the glacier has been it leaves behind moraine on the

floor of the valley called ground moraine, till or boulder clay.

Melting Glacier TillOutwash Plain

Terminal MoraineDrumlins

How Drumlins are formed1. The temperature rises due to climate change at the end of the

ice age.2. The glacier begins to melt. The snout moves back up the

valley. 3. The melting ice cannot hold the rocks, gravel and sand that

have been trapped in it. 4. All this material is deposited as the glacier continues to melt. 5. The moraine is all mixed up with different sizes of material. 6. A large rock is deposited and traps more moraine around it

forming a drumlin7. The glacier continues to move when it is melting and makes

the drumlin smooth

Melting Glacier TillOutwash Plain

Terminal MoraineDrumlins

How Terminal Moraine is formed1. The glacier pushes the moraine in front of it like a bulldozer2. The temperature rises due to climate change at the end of

the ice age.3. The glacier begins to melt. The snout moves back up the

valley. 4. The melting ice cannot hold the rocks, gravel and sand that

have been trapped in it. 5. All this material is deposited as the glacier continues to melt. 6. The moraine is all mixed up with different sizes of material7. The furthest point the glacier reached is marked by a ridge

of material running across the valley called terminal moraine

Melting Glacier TillOutwash Plain

Terminal Moraine

Melting Glacier TillOutwash Plain

Terminal MoraineDrumlins

How the outwash plain is formed1. The temperature rises due to climate change at the end of

the ice age.2. The glacier begins to melt. The snout moves back up the

valley and melt-water streams carry material down the valley.

3. The outwash plain is in front of where the glacier has been and is deposited by melt-water.

4. The outwash plain is made from sorted sands and gravels.5. Gravels are deposited in the spring when there is more

melting. Sands are deposited in the autumn when there is less melting

Melting Glacier TillOutwash Plain

Ter

min

al M

ora

ine

Drumlins

How an esker is formed

1. The temperature rises due to climate change at the end of the ice age.

2. The glacier begins to melt.3. Tunnels form in the melting ice4. Meltwater streams flow in the

tunnels 5. Deposits are laid down along

the course of where the stream has been.

6. The snout moves back up the valley

7. Long, winding ridges of sorted material known as eskers are left where these streams have been

8. Gravels are deposited in the spring when there is more melting. Sands are deposited in the autumn when there is less melting