Topic 2 - Glaciation: EQ3

Question 1

Cirque

Answer 1

Description - An amphitheater-shaped depression in a mountainside with a steep back wall and a rock lip.
Formation - Large rounded hollow high on a mountainside is eroded and deepend by plucking and abrasion due to the rotatioal ice movement of a cirque glacier.

Question 2

Pyramidal peak

Answer 2

Description - Apointed mountain peak with three or more cirques\
Formation - The erosional processes nearby cirques mean they erode backwards towards each other, creating a sharp edge, pointed mountain. Plucking important

Question 2

Arête

Answer 2

Description - A narrow, kinfe edged ridge between two cirques.
Formation - Plucking an d abrasion on the back of of the wall of two cirques on a mountainside mean they erode backwards towards one another, creating a narrow ridge. Freew thaw action also important.

Question 3

Glacial trough

Answer 3

Description - A U-shaed valley with steep sides and a wide, flat floor
Formation - A V shaped river valley is widened and deepened as a result of powerful plucking and abrasion by a valley glacier, which goes through the landscape rather than around it.

Question 4

Hanging Valley

Answer 4

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

Question 4

Truncated spur

Answer 4

Description - A steep rocky valley side where spurs of a river valley used to interlock before glaciation.
Formation - valley glaciers are less flexible than rivers and remove the ends of interlocking spurs by plucking and abrasion as they ove down the river valley.

Question 5

Ribbon lake

Answer 5

Description - A long, narrow lake along the floor of a glacial trough
Formation - Increased plucking and abrasion by the valley glacier deepen part of the valley floor, as a result of either the confluence of glaciers or weaker rocks. Sometimes the lake forms behind a terminal moraine after glaciation.

Question 6

Roche moutonnée

Answer 6

Description - A mass of bare rock on the valley floor with a smooth stoss and a steep jagged lee.
Formation - A more resistant rock causes ice movement by creep and regeation around it. As the ice slides over the rock, it scours and smooths the stoss, while refreezing on the lee causes plucking.

Question 7

Knock and lochan

Answer 7

Description - A lowland area with alternating small rock hills and hollows, often containing small lakes.
Formation - Scouring at the base of a glacier excavates areas of wealer rock, forming hollows that fill with melt water and precipitation following ice retreat.

Question 8

Crag and tail

Answer 8

Description - A very large mass of hard rock forms a steep stoss with a gently sloping tail of deposited material
Formation - A 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, but he sheltering effect diminishes with distance, creating a sloping tail.

Question 9

Glacial landforms, Macro scale

Answer 9

Ice-sheet-eroded knock and lochan landscapes, cirques, arêtes and pyramidal peaks. Glacial troughs, ribbon lakes, till plains, terminal moraines, sandurs

Question 10

Glacial landforms, Meso scale

Answer 10

Crag and tail, roches moutonnees,drumlins , kames eskers amd kame terraces, kettle holes

Question 11

Glacial landforms, Micro scale

Answer 11

Features such as striations, glacial grooves and chattermarks , erratics

Question 12

Types of glacial erosion, Abrasion

Answer 12

Explaination - Rock fragments frozen into the base of moving ice grind down bedrock, eroding it and generating fine eroded material called rock flour
Evidance - Glacially eroded rock surfaces often have striations

Question 13

Crushing

Answer 13

Explanation - The pressure exerted by rock fragments embedded at the base of ice can chip fragments off the bedrock below.
Evidance - Micro features called chattemarks are evidance of fractering by crushing forces

Question 14

Plucking

Answer 14

Explanation - Plucking removes chunks of bedrock by freezing water around them os they are pulled away by the ice mass as it moves over the top
Evidance - Plucking produces steep rock faces with numerous fractures and an angular pattern of missing blocks

Question 15

Basal melting

Answer 15

Explanation – This process is similar to abrasion in rivers, but differs because water flowing at the base of ice can be under pressure, making abration a more powerful force
Evidance - Deeply eroded channels and potholes can indicate areas where basal meltwater flow occurred in the past

Question 16

Glacial debris 3 types

Answer 16

Once rock has entered the glacial system and it is being transported, it is classified into three kinds of debris -
Supraglacial, material is carried on top of the glaciers surface
Englacial, material is carried within the body of the glacier
Subglacial, material is moved along at the base of the glacier

Question 17

Lodgement till

Answer 17

Spread onto the valley floor beneath the ice by glaciers

Question 18

Ablation till

Answer 18

Is dropped by a glacier as it melts. The till is mainly deposited close to the glacier snout because this is where most ablation happens - the glacier drops debris as the ice around the debris melts.

Question 19

Lateral moraine

Answer 19

Appearance - A ridge of moraine along the edge of the valley floor
Formation - Exposed rock on the valley side is weathered and fragments fall down on to the edge of the glacier. This is then carried along the valley and deposited when the ice melts, parallel to ice flow.

Question 20

Medial Moraine

Answer 20

Appearance - A ridge of moraine down the middle of the valley floor
Formation - When two valley glaciers converge, two lateral moraines combine to form a medial moraine. Material is carried and deposited when melting occurs, parallel to ice flow

Question 21

Terminal Moraine

Answer 21

Appearance - A ridge of moraine extending across the valley at the furthest point the glacier reached
Formation - Advancing ice carries moraine foward and deposits it at the point of maximum advance when it retreats. The up valley side is generally steeper than the other side as advancing ice rose over the debris, this is transverse to the ice flow.

Question 22

Recessional moraine

Answer 22

Appearance - A series of ridges running across the valley behind the terminal moraine
Formation - Each recessional moraine, and there may be many, represents a still - stand during ice retreat. They are good indicators of the cycle of advance and retreat that many glaciers experience. Transverse to ice flow

Question 23

Push moraine

Answer 23

Appearance - A ridge of moraine with stones tilted upwards Formation - Any morainic material at the glacier snout will be pushed foward during adavnce. The faster the velocity of advance, the steeper the angle of tilt or stones. Transverse to ice flow.

Question 24

Sub glacial drumlins

Answer 24

Rounded mounds formed parrllel to ice flow, with broad upstream ends and a tapered downstream end. The streamlined shape causes minimal resistance to ice flow, found in drumlin fields can be up to 100m hugh, 1500m long and 500m wide.

Question 25

Till plains

Answer 25

Large relatively flat plain or undulating landscape of till in a lowland area. When a sheet of ice retreats, large amounts of materila are deposited over a sizeable area.

Question 26

Reconstructing past glaciation using relict glacial landscapes

Answer 26

A number of erosional and depositional landforms can be mapped to indicate the direction of ice movement including, striations, roche moutonnees, glacial troughs, crag and tail and drumlins.

Question 27

how can till fabric analysis and cirque orientation be used?

Answer 27

As a glacier moves, it turns the larger rock fragments to point in the direction of the ice movement. Therefore it is possible to study the orientation of the clasts to understand the former ice movement.

Question 28

How can drumlin orientation be used?

Answer 28

example - South of Appleby, Drumlin field left behind indicates the directionof movement, and the large volume of material eroded, transported and deposited.

Question 29

How can erratics be used?

Answer 29

Erratics give clues to establish the direction of previous ice movement. By working out the source of the erratic the origin of the ice can be established e.g. volcanic material from Ailsa craig has been founs 250km south on the Lancashire plain. The limitations of using erratics is that a number of erosinal processes could have occured on the movement of the debris, e.g. weathering and human activity could get rid of small eratics.

Question 30

Kames

Answer 30

Terrace kames are formed parrallel to the direction of glacial ice movement. They consist largely of sand and gravel deposited by streams in the final stages of a glacial period. 3 types kame terraces, kame deltas and crevasse kames. The limitations are kames only show localised movement of ice and are not repressentitive, can be altered and mdified by weathering or by humans.

Question 31

Eskers

Answer 31

Can be used to indicate the direction of movement. Most subglacial ice streams are in the direction of glacial movement. Eskers could be altered by weathering or repeated glaciations, the assumption is made that melt water and ice flow are in similar directions.

Question 32

Outwash plains

Answer 32

Large icesheets have a meltwater plain or sandurs in front of the ice, which can be used to infer the edge of the ice and where it starts. These out wash plains are varying easily modified by past glacial activities. Iceland has many volcanoes which are activites causing flash flooding which can turn up the plains.

Question 33

Meltwater channels

Answer 33

Can be used to indicate direction of ice movement of most subglacial ice streams after in the direction of of glacial ice movement. It is assumed that the melt water and ice flow are in similar directions and can be confused for erosional landforms.

Question 34

What are fluvial glacial landscapes

Answer 34

Means river and glacial. The landscape created by fluvial glacial process are assoisated with water flowing.

Question 35

Sandur

Answer 35

A falt expanse of fluvio-glacial debris in front of the glacier snout. As melt water streams emerge from the glacier and enter lowland areas they gradually lose energy and deposit debris load.

Question 36

Kettle hole

Answer 36

A circular depression, often forming a lake in an outwash plain, as the glacier retreats, detached blocks of ice remain on the outwash plain. Meltwater stream flow over the ice, covering them in deposits of fluvioglacial debris.

Question 37

Proglacial lake

Answer 37

A lake formed in front of the glacier snout. A proglacial lake is often formed by the damming action of a terminal or recessonial moraine during the retreat of a melting glacier, or because hills block the escape of meltwater

Question 38

Meltwater channel

Answer 38

A narrow channel cut into bedrock or deposits, either underneath or along tje front of an ice margin, Meltwater can erode deep channel seven gorges as a result of the hihg hydostativ pressure within the glacier an dtheir high sediment load.