Glaciated Landscapes EQ 3

Question 1

Arête

Answer 1

A narrow knife-edged ridge between two cirques.
Plucking and abrasion on the back wall on the two cirques mean they erode towards one another, creating a narrow ridge. Freeze thaw is also important

Question 2

Glacial erosion processes

• abrasion
• plucking
• crushing
• basal sliding

Answer 2

Abrasion- material rubs against The Valley sides and floor, wearing them away by a process similar to sandpaper

Plucking- when meltwater freezes the underlying bedrock to the base. Any loose rock fragments are plucked away as the glacier slips forward.

Crushing- the direct fracturing of weak bedrock by the wight above it

Basal melting- large volumes of meltwater can cause fluvial erosion such as abrasion, hydraulic action, attrition and corrosion.

Question 3

Pyramidal peak

Answer 3

A pointed mountain with 3 or more cirques.

Erosion backwards creating a sharp pointed mountain summit.

Question 4

Glacial trough

Answer 4

A u shaped valley with steep sides and a wide flat floor.

Formed when a v shape valley is widened and deepened as a result of plucking and abrasion

Question 5

Truncated spur

Answer 5

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

Question 6

Hanging valley

Answer 6

A small tributary v-shaped or u-shaped valley high above one glacier floor, often with a waterfall.

Glacial ice erodes downwards faster than thinner ice in tributaries. The floor of tributaries are left high above the main valley floor.

Question 7

Ribbon lake

Answer 7

Areas of increased plucking and abrasion by The Valley glacier deepen part of The Valley floor.

Question 8

Crag and tail

Answer 8

Is formed when a very large resistant object or crag, obstructs the flow of a glacier. The ice forced around the obstruction eroding weaker rock. However material in the lee (shelter side) of the obstruction is protected by the crate and leans the formation of a gently sloping tail of deposited material.

Question 9

Knock and lochan

Answer 9

A glacially scoured lowland area which has alternating Roche moutonnée and eroded hollows which often contain small lakes. They are often found on rocks where alternate resistant and weekly jointed rocks as this allows differential erosion.

Question 10

Roche moutonée

Answer 10

The stoss is smoothed and polished by abrasion but plucked on the lee side. This is because increased pressure on the stoss side cause the ice to melt over the out crop of rock. When it reaches the lee the water refreezes as there is less pressure. Loose rock is frozen to the base and when the glacier slips loose rock is pulled away creating a jagged edge by plucking.

Question 11

Medial moraine

Answer 11

Is formed when two glaciers meet and lateral moraines come together on the surface. When the glacier melts sediment is dropped as unsourced angular morainic material and a medial moraine is left on The Valley form.

Question 12

Terminal moraine

Answer 12

A prominent ridge of glacial debris formed when a glacier reaches its maximum limit during sustained advance.

Question 13

Lateral moraine

Answer 13

Debris deposited along the side of the glacier, comprising both rockfall debris from above and debris ground up by the ice marginal process

Question 14

Recessional moraine

Answer 14

Ridge of debris representing a stationary or minor re-advance phase during otherwise general retreat.

Question 15

Till plains

Answer 15

When a sheet retreats, large amounts of material are deposited over a sizeable area due to melting.

Question 16

Lodgement till

Answer 16

Till is deposited by actively moving ice forming landforms such as drumlins.

Question 17

Ablation tills

Answer 17

Till deposited by melting ice from stationary or retreating glaciers forming landforms such as terminal and recessional moraines.

Question 18

What is stratified

Answer 18

Layered

Question 19

What is sorted

Answer 19

Large material at the bottom

Question 20

Drumlins

Answer 20

There are two theories
The most accepted: drumlins are formed when the ice is overloaded with lodgement till and capacity to carry it to reduced as it negotiates with obstacles beneath it. This results in lodgement till being deposited creating a blunt stoss end upstream of advanced ice and a tapered lee slope.

Question 21

Drumlins alternate theory

Answer 21

Material is deposited due to friction between ice and the underlying geology, causing the glacier to deposit its load. As the glacier retreats it streamlines its mould.

Question 22

Ice contact features depositional

Answer 22

Moraines
Drumlins
Till

Question 23

Ice contact features formed by Fluvio glacial

Answer 23

Kames
Kame terraces
Eskers

Question 24

Ice contact features proglacial

Answer 24

Sanders (outwash plains)
Proglacial lakes
Meltwater channels
Kettle holes

Question 25

Kames

Answer 25

Are mounds of sand gravel which are stratified and sorted, found on The Valley floor. Meltwater streams on top of glaciers collect in depressions and deposit layers of debris. When the ice melts the debris is dumped onto The Valley floor.

Question 26

Kame terraces

Answer 26

During the summer The Valley sides radiate heat and melt the ice. This releases meltwater traps sediment on The Valley side. When the glacier retreats sediment is dropped to The Valley floor. They look like lateral moraine but there are sorted and stratified due to meltwater.

Question 27

Eskers

Answer 27

Are long winding ridges of sand and gravel that run in the same direction of the glacier. There deposited by meltwater streams flowing in tunnels underneath the glacier. When the glacier retreats and the stream dries up the load remains as an esker. Eskers show you where the glacial used to be. They are stratified and sorted.

Question 28

Kettle holes

Answer 28

Blocks of ice detach from the glacier by ice calving and become buried by out wash. When ice melts a depression is left.

Question 29

Proglacial lake

Answer 29

Can form in front of glaciers when the floor from meltwater streams get dammed by a terminal moraine

Question 30

Outwash plain

Answer 30

Sediment on the outwash plain are sorted into layers. Gravel gets dropped first because its heavier than sand and clay. Clay is dropped last and is carried furthest away from the snout because it is the lightest.

Question 31

Meltwater channels

Answer 31

When glacial ice melts, water runs out and forms streams of meltwater. Surface meltwater filters through the glacier and flows through tunnels underneath the glacier before running out the snout. Meltwater cause erosion however they cause more erosion to rivers of the same size. This is because of pressure the ice causes.

Question 32

Imbrication

Answer 32

When rocks are on there a axis as it is the most streamlined

Question 33

How is a cirque formed

Answer 33

A hollow is enlarged by nivation and snow accumulates in the hollow and is compresses turning into glacial ice. When ice reaches a critical weight (more than 30m thick) it starts to move by rotational slip eroding the floor and back wall by plucking and abrasion. Frost shattered scree form the back wall falls into the berg shrud and becomes entrainment. There is a rock lip at the front of the cirque and where there is a change in gradient there is less erosion and more deposition.

Question 34

How ice sheet scouring causes the formation of landforms

Answer 34

• ice sheet scouring happens when ice sheets are slowly moving through a landscape by basal sliding and deformation.
• tend to be in areas of alternating rock, so there are different rates of erosion
• erosion processes are abrasion and plucking
• they create landforms such as knock and lochan, crag and tail and Roche moutonées
• Roche moutonees are formed when ice flows over a resistant obstacle, the taped stoss is formed by abrasion and the jagged lee by plucking.