G - Glacial Landforms

Question 1

How do glaciers create basins?

Answer 1

-Snow collects in hollows (usually in the side with the most accumulation ad least ablation)
-Snow collects in hollows and turns into ice. Basal sliding with abrasion and plucking deepen the hole into a corrie
(When the ice in the hollow is thick enough, it flows over the lip and downhill as a glacier - frost shattering an plucking steepen the back wall of the corrie

Question 2

Name as many glacial erosion landforms as you can (10 in total)

Answer 2

• Arete
• Pyramidal peak
• Glacial trough
• Hanging valley
• Truncated spurs
• Valley steps
• Tarns
• Ribbon Lakes
• Fjords
• Roche mountenée

Question 3

What is an arête?

Answer 3

A steep sided ridge

Question 4

How is an arête formed?

Answer 4

Formed when two glaciers flow in parallel valleys. The glaciers erode the sides of the valley, which sharpens the mountain ridge on between them

Question 5

What is a pyramidal peak?

Answer 5

A pointed mountain peak with at least three sides

Question 6

How is a pyramidal peak formed?

Answer 6

Where three or more corries from back to back (their back walls make the mountain peak)

Question 7

What is a glacial trough?

Answer 7

(Also called a U-shaped valley) - steep sided valleys with flat bottoms

Question 8

How is a glacial trough formed?

Answer 8

By the erosion of a V-shaped river valleys by glaciers, as the glacier erodes through the v-shaped it makes them deeper and wider

Question 9

What is a hanging valley?

Answer 9

Valleys formed by tributary glaciers

Question 10

How is a hanging valley formed?

Answer 10

When tributary glaciers erode the valley floor much less deeply because they’re smaller than the main glacier - so when the glaciers melt, the valleys get left at a higher level than the glacial trough formed by the main glacier
→ You get waterfalls from hanging valleys into the main glacial trough

Question 11

How are truncated spurs formed?

Answer 11

When ridges of land (spurs) that stick out into the main valley are chopped off (truncated) as the main valley glacier moves past

Question 12

What are valley steps?

Answer 12

Steps in the glacial trough

Question 13

How are valley steps formed?

Answer 13

When the glacier erodes the valley floor more deeply - this happens when another glacier joins it or where there’s less resistant (softer) rock

Question 14

What are tarns?

Answer 14

Lakes that form in corries after a glacier has retreated

Question 15

What are ribbon lakes?

Answer 15

Long, thin lakes that form after a glacier retreats

Question 16

Where do ribbon lakes form?

Answer 16

In dips caused by erosion of bands of less resistant rocks, or behind dams of debris left by the glacier

Question 17

What are Fjords and how do they form?

Answer 17

Long, deep inlets that form when a valley that’s been eroded by a glacier is flooded by sea level rise after the ice has melted

Question 18

What is a roche mountenée?

Answer 18

A resistant (hard) mass of rock on the valley floor

Question 19

Explain how a roche mountenée forms and why?

Answer 19

The upstream (stoss) side is smooth, due to abrasion as the glacier went over it. The downstream (lee) side is steep and rough where the glacier plucked at it

Question 20

What is moraine?

Answer 20

Formations of till deposited by a glacier as it melts

Question 21

What are the types of moraine? Explain them (formation)

Answer 21

Lateral moraine - deposited where the sides of the glacier were
Medial moraine - Formed from the two lateral moraines of two glaciers merge
Terminal/end moraine - marks the furthest point that the glacier reached, often a high mound/series of mounds of debris that extend across a valley
Recessional moraine - often parallel to terminal moraine - mark the retreat of a glaciers retreat - each recessional moraine reflects a stage when glacial retreat was halted long enough for deposition to concentrate in 1 area
Subglacial - beneath the glacier
Englacial - inside the glacier
Supraglacial - debris accumulated on top of the ice

Question 22

What are drumlins? Name and explain its features an give an example of a group

Answer 22

Smooth, asymmetrical, elongated mounds of till
The upstream side is the stoss side which is wide and tall
The downstream side is the lee side which is narrow and low
There are a group of Drumlins in the Ribble Valley, Lanchashire

Question 23

What are the measurements for till?

Answer 23

Up to 1500m long and 100m high

Question 24

What are Erratics? An example?

Answer 24

Rocks that have been picked up by a glacier or an ice sheet, carried along and dropped in an area of completely different geology
eg in Eastern England that were originally picked up by an ice sheet in Norway and carried to England