Landforms Created by GlaciersAim: To describe and explain how erosion

by glaciers create Corries, Arêtes, and Pyramidal Peaks.

Starter: Complete the worksheet by writing in the definitions then trying to work out what the glacial features are.

Arete: An arête is a knife-edge ridge. It is formed when two neighbouring corries run back to back. Corrie: A corrie is a rounded, armchair shaped hollow with a steep back wall on the side of a mountain.Pyramidal Peak: A pyramidal peak is formed where three or more corries and Arêtes meet. It is the point at the top of a mountain.Tarn: Is a lake found in the bottom of a corrie.

Before Glaciation – V shaped valleys, rounded hills

During Glaciation – Glacial processes begin to change the shape of the landscape

After Glaciation – U shaped valleys, steep sided mountains.

video

What does a pre-glacial landscape look like?

What does a glacial landscape look like?

What does a post-glacial landscape look like?

How did you do?

Recap

• Time for a quick re-cap on what you learnt last lesson...

• Each row of tables has to answer one of the questions.

• Everyone else needs to listen and write down the answer.

Q1. What does ice do to the landscape? (one thing!)

A1. What does ice do to the landscape? ICE ERODES THE LANDSCAPE (✔)

Q2. Name and describe this feature.

A2. Name and describe this feature.

V-SHAPED VALLEY (✔)

Narrow valley floor(✔)

Very Steep sides(✔)

Q3. Q3. Name and describe this feature.

Q3. A3. Name and describe this feature.

U-SHAPED VALLEY (✔)

Wide, Flat Valley Floor (✔)

Steep Valley sides (✔)

Q4. What 3 erosion processes makes a valley go from A to B?

A B

HINTS

A4. What 3 erosion processes makes a valley go from A to B?

A B

PLUCKING (✔)ABRASION (✔)

and FREEZE-THAW WEATHERING(✔)

So how are these features created?

Pyramidal Peak

Arete

Corrie

The eroding ice carves out steep mountain sides. Ridges called arêtes stand out against the sky. Hollows

called corries develop below them on the mountain sides

Corrie

Arête

PyramidalPeak

© Trevor Cole

How is a Corrie formed?Snow collects in a natural hollow on the side of a mountain. Over time, further snow collects in the hollow. This extra weight compresses the snow underneath, turning it into ice.

The hollow is deepened and widened by the corrie glacier through the processes of abrasion and plucking.

This over-deepening leads to an ‘armchair’ shape characteristic of a corrie and causes a ‘rock lip’ to be formed.

Explain how is a Corrie formed (4)

Use the information in the video and the information provided to help you annotate the formation of a corrie.

As snow gathers and piles up the pressure forms ice and it starts to move downhill

The process of plucking steepens the back of the corrie.

Ice rotates, scooping out the floor of the corrie

Water may gather on the floor of the corrie. This is know as a tarn

Frost action make the mountain jagged.

A Corrie in pictures! Cwm Idwal

Tarn

Bowl-shaped corrie

Steep back-wall

Task: Draw an annotated sketch of the glacial features

Annotations to help....

Arm chair shaped hollow that snow and ice accumulate in, carved by a glacier

Tarn formed in the deepest part of the corrie as it was scooped out by erosion (abrasion)

Steep back wall caused by freeze-thaw and plucking

Rock lip at the edge of the corrie formed by deposits as the glacier rotated out of the basin

Corrie on Maps

Arete

Sharp knife edged ridge between TWO corries.

Formed as two corries are eroded and weathered backwards.

Corrie

An arm chair shaped hollow widened and deepened by a glacier.

Steep back wall created by freeze-thaw and plucking

Named example

Striding Edge on Helvellyn in the Lake District

Add to your corrie exam answer…How is an arete formed? (4)

How does a Corrie form an Arête and a Pyramidal Peak?

Formation of an arête

Arêtes are ‘knife-edged’ ridges formed between two corries.

Label the Pyramidal Peak Diagram

Pyramidal peaks are formed when three or more corries cut backwards into the same mountain.

Formation of a pyramidal peak

corrietarn

arête

Task

• Create a 6-10 step annotated diagram to explain the formations of a corries, aretes and pyramidal peaks

Have a go with play dough...Explain to the person next to you the processes that create

a pyramidal peak.

Who is ready and willing to give a demonstration to the class?