Glacio-fluvial landforms

Question 1

what are glacio-fluvial landforms?

Answer 1

exists as a result of climate change at the end of glacial periods
produced by meltwater from glaciers

Question 2

What is outwash?

Answer 2

sediment deposited by glacio fluvial streams

Question 3

how does outwash compare to till?

Answer 3

smaller as meltwater streams have less energy than glaciers (carry finer material)

Smooth and rounded (contact of water and attrition)

Sorted

Stratified (distinctive seasonal and annual layers)

Question 4

When is meltwater streams highest discharge?

Answer 4

Summer months which enables them to carry very large cobbles + boulders

Question 5

What are jökulhaulps?

Answer 5

Extreme glacial outbursts caused by geothermal/volcanic activity beneath glaciers that cause massive + sudden melting

Question 6

What are the four main types of erosion?

Answer 6

Hydraulic action - force of water erodes the bed + banks of meltwater channel. Meltwater forces air into fissures in the bed + banks of channel = pressure cavitation = material loosened. Then material carried away by the stream in times of high discharge to be deposited in outwash plain.

Abrasion - stones in transport within the water thrown at bed + banks of meltwater channel, eroding them. This process can over deepen + widen the meltwater channel.

Corrosion - where weak acids within water react with rocks, bed + banks of the channel. This erosional process will take place when rock is affected by acids eg limestone.

Attrition - rock fragments in transport thrown into one another during channel turbulence.

Question 7

What are examples of glacio-fluvial landforms from deposition?

Answer 7

Kames, Eskers, Outwash plains

Question 8

What is a kame?

Answer 8

Hill composed of stratified sand + gravel laid down by glacial meltwater.

These mounds build up in height as a glacier melts and meltwater streams carry material from within and on top of the glacier to be deposited immediately in front of the glacier into meltwater lakes.

1. rock fall from valley falls on top of the glacier. the rock/sediment then fall into the crevasses in the glacier
2. as deglaciation occurs, the crevasses move down closer + closer to the base as the glacier melts
3. when they reach the valley bed once the glacier has almost melted, they are dumped onto the bed as a mound of sediment

Question 9

What are the two types of kame?

Answer 9

Delta kames, kame terraces

Question 10

How are delta kames formed?

Answer 10

result from the fluvial deposition of sediments in surface crevasses. when the ice melts they are deposited as small hummocks on the valley floor.

Question 11

What are kame terraces? and how are they formed?

Answer 11

Ridges of material running along the edge of the valley floor

Supra glacial streams on edge of glacier pick up + carry lateral moraine, later deposited on valley floor as glacier retreats.

1. pressure between the glacier + valley sides forms a ice marginal channel
2. as water (carrying sediment) travels into the valley, it collects in the ice marginal channel
3. the ice marginal channel is not moving at all so the material is deposited here
4. when the glacier retreats it leaves the material at the valley sides

Question 12

How do supra glacial streams form?

Answer 12

Due to melting ice warmed by valley sides as result of friction + heat retaining properties of valley side slopes

Question 13

how are supra glacial streams different from lateral moraine?

Answer 13

They are composed of glacio fluvial deposits that are rounded + sorted

Question 14

what is an esker and how are they formed?

Answer 14

A long, sinuous ridge composed of stratified sand + gravel laid down by glacial meltwater. eg Munro Esker, Canada

1. An esker is formed when there is a sub-glacial meltwater channel flowing within the body of the glacier, this is due to increased pressure on the base of the glacier.
2. The channel carries sediment in the glacier + entrains sediment. -> moves forward at a very fast rate due to hydrostatic pressure in the glacier
   (Sub glacial streams may carry huge amounts of debris under pressure in confined tunnels at the base of the glacier)
3. when the glacier retreat, the stream stops moving as hydrostatic pressure is lost. Deposition occurs when pressure is released + meltwater emerges at the snout.
4. As glacier snout retreats, the point of deposition will gradually move backwards. (Explains why eskers are beaded)

Question 15

What is an outwash plain?

Answer 15

Flat expanse of sediment in pro glacial area. Typically braided streams - river channels subdivided by numerous islets + channels.

Question 16

how are outwash plains formed?

Answer 16

formed in front of glacier, as meltwater streams gradually loose energy, as they enter lowland areas beyond the ice front, they deposit their load.

1. Discharge occurs from both the melting snout of the glacier and the emergence of meltwater streams from within the body of the glacier.
2. The finest sediments are carried further away from the glacier. Coarser materials are deposited nearer to the snout of the glacier as the meltwater drops these first as its energy declines.
3. During times of higher discharge, particularly in the summer months when glacial ablation is high, braided meltwater streams will intersect the plain as the balance of erosion/deposition shifts temporarily towards net erosion closer to the ice front.

Question 17

How does temperature effect these deposition landforms?

Answer 17

Outwash plains - as temperature rises, further melting + retreat of glaciers = production of more meltwater + thus greater expanse + accumulation of outwash material in the pro glacial area

Kames + eskers - exposed in greater no. + of greater length during this continued retreat.

cxt - Solheimajokull is retreating about 100m/year + within a couple of decades a pro glacial lake will probably form at the snout

Exposed outwash material - temp increases, growing season increases for vegetation. Becomes colonised overtime, first by mosses, then lichens, then by grasses, flowering plants + shrubs

Question 18

how are kames effected by climate change?

Answer 18

melting bc temp is warming, happened at the end of ice age, more melting also due to current climate change -> more deposition

Past climate changes
As climate warmed increased melting
would lead to increased deposition of stratified material which is sorted and rounded as well as increased exposure of the kames
Cycle of retreat and advance over years would modify kames as erosion rates increase

Question 19

how are eskers effected by climate change?

Answer 19

1. warming = lots of meltwater, carries material

2. more evaporation thus loses energy + deposits material