Erosional Landforms

Question 1

Arete description:

Answer 1

A narrow, knife-edged ridge between two cirques

Question 2

Arete formation:

Answer 2

Plucking and abrasion on the back wall of two cirques on a mountainside mean they erode backwards towards each other, creating a narrow ridge.

Question 3

Pyramidal peak description:

Answer 3

A pointed mountain peak with three or more cirques

Question 4

Pyramidal peak formation:

Answer 4

Plucking and abrasion cause two or more cirques to erode backwards towards each other, creating a sharp, pointed mountain summit

Question 5

Glacial trough description:

Answer 5

A U-shaped valley with steep sides and a wide, flat floor

Question 6

Glacial trough formation:

Answer 6

V-shaped river valley is widened and deepened as a result of powerful plucking and abrasion by a valley glacier, going through the landscape

Question 7

Truncated spur description:

Answer 7

A steep rocky valley side where spurs of a river valley used to interlock before glaciation

Question 8

Truncated spur formation:

Answer 8

Interlocking spurs, which predate the glacier, are eroded via abrasion and plucking and amputated by the strong, flowing glacier forcing its way through a valley

Question 9

Hanging valley description:

Answer 9

A small tributary V shaped, or U shaped valley high above the main glacial trough, often with a waterfall as the river flows over the edge

Question 10

Hanging valley formation:

Answer 10

Powerful, thicker glacial ice in the main glacial trough eroded vertically downwards more rapidly than thinner ice or rivers in tributary valleys. The floors of the tributary valleys are left high above the main valley floor

Question 11

Ribbon lake description:

Answer 11

A long, narrow lake along the floor of a glacial trough

Question 12

Ribbon lake formation:

Answer 12

Areas of increased plucking and abrasion by the valley glacier deepen parts of the valley floor, as a result of either confluence or less resistant rock. Rainwater fills these deeper areas creating a lake.

Question 13

Roche moutonnee description:

Answer 13

A mass of bare rock on the valley floor with a smooth stoss (up-valley side) and a steep jagged lee (down-valley side)

Question 14

Roche moutonnee formation:

Answer 14

More resistant rock causes ice movement around it by creep and regelation. As the ice slides over the rock, it scours and smoothes the stoss, while refreezing on the lee and causing plucking

Question 15

Knock and lochan description:

Answer 15

A lowland areas with alternating small rock hills (knock) and hollows, often containing small lakes (lochan)

Question 16

Knock and lochan formation:

Answer 16

Scouring at base of a glacier excavates areas of weaker rocks, forming hollows that fill with meltwater and precipitation following ice retreat

Question 17

Crag and tail description:

Answer 17

A very large mass of hard rock forms a steep stoss with a gently sloping tail of deposited material

Question 18

Crag and tail formation:

Answer 18

A large mass of hard rock is resistant to ice scouring and creates a steep stoss. Reduce glacier velocity on the lee protects softer rocks and allows deposition, but the sheltering effect diminishes with distance, creating a sloping tail

Question 19

Glacial striations description:

Answer 19

Series of long, straight parallel lines/scratches cut into the bedrock surface of a rock

Question 20

How is a cirque formed?

Answer 20

1. Snow accumulates in a hollow
2. Snow forms neve and then turns into ice
3. Ice moves by rotational slip due to gravity
4. This deepens and widens the corrie
5. Abrasion smooths the bottom of the corrie creating the corrie lip
6. Steep back wall is formed by plucking
   e. g. Cwm Idwal, Snowdonia