3.1.4.4 Fluvioglacial Landforms

Question 1

What is produced when glaciers melt to transport a lot of debris

Answer 1

Huge quantities of meltwater

Question 2

What are meltwater streams like

Answer 2

Often flow under pressure so have high velocity + turbulent flow.
Can pick up + transport a larger amount of material than normal rivers can

Question 3

What causes meltwater to deposit material

What’s this material like when it’s deposited

Answer 3

It’s discharge decreasing causing energy loss

Heavier particles are dropped first so material is sorted. Can also be found in layers due to seasonal variations in meltwater flow

Question 4

Describe a fluvioglacial landscape

Answer 4

• Meltwater
• wide multi-channelled (braided) river flowing over a vast area of 2 types of sediment
• very dynamic landscapes with river channels migrating + changing course

Question 5

2 types of sediment in a fluvioglacial landscape

Answer 5

Poorly sorted angular glacial till

Well sorted more rounded out wash (sandy/gravelly)

Question 6

2 fluvioglacial landforms due to erosion

Answer 6

Meltwater channels

Proglacial lakes + overflow channels

Question 7

Describe meltwater channels

Answer 7

When glacial ice melts, it’s water forms streams of meltwater
It flows through tunnels underneath the glacier before running out of the snout

Question 8

Why do meltwater streams cause more erosion than rivers

4 types of erosion

Answer 8

Due to the ice’s pressure causing meltwater to flow very quickly

Abrasion
Attrition
Solution
Hydraulic action

Question 9

How do meltwater channels form

Answer 9

Meltwater streams form deep troughs in the landscape called meltwater channels.

As meltwater streams have a lot of erosive power, the meltwater channels produced are very wide + deep

Question 10

Describe proglacial lakes + overflow channels

Answer 10

During deglaciation, lakes develop on edges of ice, some occupying large areas
Overflows that cross lowest points for the watersheds will create new valleys
When the ice dimming these meltwater lakes melts, many new valleys are left dry

Question 11

What was the huge proglacial lake formed as ice blocked the River Severn valley

Answer 11

Lake lapworth

Question 12

How did the river Severn and lower Severn form one

What did it form in the process

Answer 12

Lake lapworth eventually overflowed the water shed to the south to join the lower Severn and when it retreated back north, the route was blocked by glacial deposits
Formed a gorge in the process

Question 13

4 fluvioglacial landforms due to deposition

Answer 13

Eskers
Kames
Kettle holes
Outwash plains (sandur)

Question 14

What are eskers

Answer 14

Long sinuous (winding) ridges of material running in direction of ice advance
5-20m high

Question 15

What do eskers consist of

Answer 15

Sorted coarse material (coarse sands and gravel)

Question 16

How do eskers form

Answer 16

Stream’s channel is restricted by ice walls causing hydrostatic pressure allowing a large load to be carried

Load builds up the bed of the channel above surrounding land/close to the snout the hydrostatic pressure may drop leading to deposition

Question 17

When is a ridge left during esker formation

Answer 17

When the glacier retreats during deglaciation

Question 18

What are kames

Answer 18

Mounds of fluvioglacial material
Deltaic deposits left when meltwater flows into a lake dammed up in front of the glacial snout by recessional moraine deposits

Question 19

What are the 3 types of kame

Answer 19

Kame terrace
Kame delta
Crevasse kame

Question 20

What’s a kame terrace

Answer 20

Most extensive kame
Results from infilling of a marginal glacial lake
When ice melts the kame terrace is abandoned as a ridge of valley side

Question 21

What’s a kame delta

Answer 21

Smaller feature that forms when a stream deposits material on entering a marginal lake

They form small,mound-like hills on the valley floor + can be identified by deltaic sedimentation characteristics

Question 22

What’s a crevasse kame

Answer 22

Kame resulting from fluvial deposition of sediments in surface crevasses
When ice melts they’re deposited on valley floor to form small hummocks

Question 23

What’s a kettle hole

Answer 23

Depression in a glaciated lowland area that usually contains a small lake

Question 24

How do kettle holes form

Answer 24

Results from blocks of ice that get detached from the icefront as the glacier retreats
These blocks get covered in glacial + fluvioglacial debris and slowly melt
As they disappear a hollow is produced on the site which later fills with water

Question 25

What’s an outwash plain (sandur)

Answer 25

An extensive, gently sloping area of sands + gravel formed in front of a glacier

Question 26

How are outwash plains (sandur) formed

Answer 26

Result from outwash of material carried by meltwater streams + rivers. At the end of a glacial period, huge quantities of meltwater will be spread out over the outwash plain.

Question 27

What season are more outwash plains formed

Answer 27

Summer (more melting)

Question 28

What distance are the coarsest material and finest material (clay) found at in outwash plains

Answer 28

Coarsest - travels shortest distance so is found near to glacier
Finest - carrier further across the plain before being deposited