3. Fluvioglacial landscapes

Question 1

What are fluvioglacial landforms?

Answer 1

Landforms that are produced by meltwater from glaciers, that form during warmer seasonal periods or during deglaciation

Question 2

What is a jokulhaulp + example?

Answer 2

An extreme glacial outburst caused by geothermal or volcanic activity beneath glaciers that causes sudden and massive melting
Eg 2010 eruption under Eyjafjallajokull ice cap led to surge of water though Markarfljot valley depositing 200,000 tonnes of sediment

Question 3

Name 3 distinctive fluvial-glacial landforms:

Answer 3

Kames
Eskers
Outwash plains

Question 4

What are the characteristics of outwash?

Answer 4

• Smaller than till as water has less energy than glaciers
• Smooth and round: subjected to erosion by meltwater
• Sorted: water deposits material based on size as the water loses energy
• Stratified: water sorts the outwash into layers

Question 5

What is a kame?

Answer 5

A hill or hummock composed of stratified sand and gravel laid down by glacial meltwater

Question 6

What are the two types of kame?

Answer 6

Delta kame

Kame terrace

Question 7

Describe the ways in which delta kames form:

Answer 7

1. En-glacial streams emerging at the snout of a glacier, losing energy at the base of the glacier and depositing its load
2. Supra-glacial streams depositing material upon entering ice-marginal lakes and losing energy
3. Debris-filled crevasses collapsing during ice retreat

Question 8

What is a kame terrace?

Answer 8

A ridge of material running along the edge of the valley floor

Question 9

How are kame terraces formed?

Answer 9

Supra-glacial streams on the edge of a glacier pick up later moraine which is later deposited on the valley floor as the glacier retreat

Question 10

How do the supra-glacial streams, which create kame terraces, form?

Answer 10

They form due to the melting of ice in contact with the valley side as the result of friction and the heat-retaining properties of the valley-side slopes

Question 11

What is the difference between kame terraces and lateral moraines?

Answer 11

Similar but kame terraces contain fluvioglacial deposits that are more rounded and sorted

Question 12

Give an example of a kame terrace:

Answer 12

In the Kingsdale Valley of the Yorkshire Dales, a kame terrace extends for about 2km along the north side of the valley and is approx 2m high

Question 13

What is an esker?

Answer 13

A long sinous ridge of stratified sand and gravel laid down by glacial meltwater

Question 14

Eskers: When is material deposited in subglacial meltwater channels?

Answer 14

As the supply of meltwater decreases at the end of the glacial period

Question 15

Eskers: When does deposition occur?

Answer 15

When the huge pressure inside the channel is released and meltwater emerged at the glacier snout

Question 16

Eskers: Why does the point of deposition move backwards?

Answer 16

Because the glacier snout retreats

Question 17

Eskers: What does it mean if an esker is beaded?

Answer 17

The ridge shows significant variation is height and width

Question 18

Give an example of an esker:

Answer 18

Trim esker near Dublin is 14.5km long and 4-15m high

Question 19

What is an outwash plain/sandur + example?

Answer 19

A flat expanse of sediment in the pro-glacial area

Eg Skeidarar Sandur, Iceland

Question 20

How is an outwash plain formed?

Answer 20

As meltwater streams use energy in lowland areas, they deposit their load with the largest material deposited nearest the ice front and the smallest being deposited furthest away

Question 21

What are outwash plains typically drained by?

Answer 21

Beaded streams

Question 22

What are beaded streams?

Answer 22

River channels subdivided by numerous islets and channels

Question 23

What does braiding begin with?

Answer 23

Begins with a mid-channel bar which grows downstream

Question 24

How does a mid-channel bar grow and how does this cause braiding?

Answer 24

Discharge decreases after a flood or period of snow melt causing coarsest particles to be deposited first
Discharge continues to decrease so finer deposits added = increasing bar size
Channel bars are then colonised by vegetation at times of low discharge
River divides around the island and re-joins

Question 25

What are the characteristics of unvegetated bars? + why are they common in outwash areas?

Answer 25

They lack stability and often move, forming and re-forming

They are common in outwash areas due to seasonal fluctuations

Question 26

Give an example of a sandur:

Answer 26

South coast of Iceland is an extensive sandur fed by numerous meltwater streams = 5km

Question 27

Why is it often difficult to identify fluvio-glacial deposits?

Answer 27

Repeated advance and retreat modifies the appearance of landforms + subject to weathering, erosion and colonisation by vegetation in post-glacial times

Question 28

What happens to each of the three major fluvioglacial landforms as temperatures increase?

Answer 28

Outwash plains = greater accumulation as increased meltwater and exposed outwash material is colonised by lichens and mosses

Kames and eskers exposed in greater numbers and will become longer