Lesson 9: Glacial Processes and Landforms

Question 1

4 glacial processes

Answer 1

Erosion
Transportation
Entrainment
Sedimentation/deposition

Question 2

Define erosion

Answer 2

Weathering of a glacial valley floor and sides by processes of freeze-thaw, weakens the rock, allowing the moving glacier to erode and remove more rock debris, which may be transported over longer distances

Question 3

3 types of transportation

Answer 3

Supraglacial
Englacial
Subglacial

Question 4

Define supraglacial

Answer 4

Mainly weathered material carried on top of the ice. Includes material falling from hillsides being washed or blown down, plus atmospheric fallout such as volcanic ash

Question 5

Define englacial

Answer 5

Formally supraglacial material, but now buried by fresh snow and carried with the ice

Question 6

Define subglacial

Answer 6

Material carried below the ice. Includes material eroded from the glacier bed and valley walls, material frozen to the base from subglacial streams, as well as englacial material that has worked its way down through the glacier or ice sheet

Question 7

Define entrainment

Answer 7

Surface sediment is incorporated into a fluid flow (air, ice, water) as part of the process of erosion

Question 8

Define deposition

Answer 8

Deposition of sediment transported by the ice occurs when it melts - mainly in the ablation zone close to he glaciers snout. Here the sediment in and on the ice melts. Water may then carry the sediment further away from the ice

Question 9

Define plucking

Answer 9

Freeze thaw weathering with basal melt water

Question 10

Define abrasion

Answer 10

Rocks being transported scratch bedrock, breaking more rock away from the base and valley walls of the glacier

Question 11

Define crushing

Answer 11

Direct fracturing of weak bedrock by the weight of the glacier, producing large angular rocks

Question 12

Define basal melting

Answer 12

Meltwater causes fluvial erosion processes such as abrasion, hydraulic action, attrition and corrosion

Question 13

Describe cirque glacier

Answer 13

Amphitheatre shaped depression with a steep back wall and rock lip

Question 14

Process of formation of cirque glacier

Answer 14

Large rounded hollow high on a mountainside is eroded and deepened by plucking and abrasion due to the rotational movement of ice

Question 15

Example of a cirque glacier

Answer 15

Cwm Idwal, Snowdonia

Question 16

Describe arete

Answer 16

Narrow, knife-edge ridge between 2 cirques

Question 17

Process of formation of arete

Answer 17

Plucking and abrasion on the back wall of 2 cirques on a mountainside mean they erode backwards towards one another. Freeze-thaw important

Question 18

Example of arete

Answer 18

Striding edge, Lake District

Question 19

Describe pyramidal peak

Answer 19

Pointed mountain peak with 3 or more cirques

Question 20

Process of formation pyramidal peak

Answer 20

Erosional processes within cirques erode backwards into each other. Plucking important

Question 21

Example pyramidal peak

Answer 21

Matterhorn, Alps

Question 22

Describe glacial trough

Answer 22

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

Question 23

Process of formation of glacial trough

Answer 23

V-shaped river valley widened and deepened from plucking and abrasion by a valley glacier which goes through the landscape rather than around

Question 24

Example of glacial trough

Answer 24

Nant Ffrancon Valley, Snowdonia

Question 25

Describe truncated spur

Answer 25

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

Question 26

Process of formation of truncated spurs

Answer 26

Valley glaciers less flexible than rivers and remove the ends of interlocking spurs by plucking and abrasion as they move down the river valley

Question 27

Example of truncated spurs

Answer 27

Mer de Glace, Alps

Question 28

Describe hanging valley

Answer 28

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

Question 29

Process of formation of hanging valley

Answer 29

Thicker glacial ice is the main glacial trough eroded downwards more rapidly than thinner ice or river tributary valleys. The floor of the tributary valleys are left high above the main valley floor

Question 30

Example of hanging valley

Answer 30

Berwyn Mountains, Wales

Question 31

Describe ribbon lake

Answer 31

Long, narrow lake along the floor of a glacial trough

Question 32

Process of formation of ribbon lake

Answer 32

Increased plucking and abrasion by the valley glacier deepen part of the valley floor, causing the confluence of glaciers or weaker rocks

Question 33

Example of ribbon lake

Answer 33

Llyn Ogwen, Wales

Question 34

Describe roche moutonnee

Answer 34

Mass of bare rock on the valley floor with a smooth stoss and a steep jagged lee

Question 35

Process of formation of roche moutonnee

Answer 35

More resistant rock outcrop causes ice movement by creep and regelation. Ice slide over rock, smooths the stoss while refreezing on the lee causes plucking

Question 36

Example of roche moutonnee

Answer 36

Lembert Dome, Yosemite NP, California

Question 37

Describe knock and lochan

Answer 37

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

Question 38

Process of formation of knock and lochan

Answer 38

Scouring at the base of the glacier excavates areas of weaker rock, forming hollows of meltwater and precipitation following ice retreat

Question 39

Example of knock and lochan

Answer 39

Shetland Islands, Scotland

Question 40

Describe crag and tail

Answer 40

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

Question 41

Process of formation of crag and tail

Answer 41

Large mass of hard rock is resistant to ice scouring and creates a steep stoss. Reduced glacier velocity on the lee protects softer rock and allows deposition - sheltering diminishes with distance - sloping tail

Question 42

Example of crag and tail

Answer 42

Castle Rock, Edinburgh