Geomorphological Erosional Landforms

Question 1

What is a cirque?

Answer 1

Armchair shaped hollow in the side of a mountain with a steep backwall

Question 2

How is a cirque formed? (4)

Answer 2

• When snow builds up in a depression or nivation hollow, it eventually compacts to form a glacier
• The glacier then gets trapped in the hollow meaning it can only move via rotational slip
• The back wall is eroded through plucking and frost shattering, hollow is deepened through rotational abrasion
• Water can fill cirques to become tarns

Question 3

What is an arête?

Answer 3

A narrow, knife like ridge formed between 2 cirques

Question 4

How is an arête formed?

Answer 4

When the back wall of 2 cirques erode into each other

Question 5

What is a glacial trough?

Answer 5

A steep sided, flat floored, straight valley

Question 6

How is a glacial trough formed? (4)

Answer 6

• A glacier erodes trough a river valley
• The glacier has enough force to erode away a river’s interlocking spurs
• This leaves smooth but steep truncated spurs on the valley sides
• The river that originally flowed through the valley will continue to flow as a ‘misfit stream’

Question 7

What is a hanging valley?

Answer 7

A smaller U shaped valley caused by a tributary glacier

Question 8

How is a hanging valley formed? (2)

Answer 8

• The smaller glacier does not have enough energy to erode to the valley floor, leaving a hanging valley
• Waterfalls often form here

Question 9

What is a truncated spur?

Answer 9

A steep and possibly rocky section of a trough

Question 10

How are truncated spurs formed?

Answer 10

The pre glacial interlocking spurs of the river are eroded by the much more powerful glacier

Question 11

What is a Roche moutonne?

Answer 11

An asymmetrical, bare rock outcrop with a gently sloping side facing up-valley

Steep = lee
Gradual = stoss

Question 12

How is a Roche moutonne formed? (6)

Answer 12

• The glacier hits an obstacle that is too large and hard to pluck, so it must move over it
• The glacier hitting the obstacle increases friction and pressure, therefore increasing melting
• This meltwater allows the glacier to slide over the rock
• When glacier reaches top of obstacle, friction and pressure drop
• Meltwater freezes
• Frozen rocks are plucked from the lee side

Question 13

What are the 6 geomorphological Erosional landforms

Answer 13

1) Cirques

2) Arêtes

3) Glacial troughs

4) Hanging valleys

5) Truncated spurs

6) Roche moutonne