Glacial Landscapes Unit 4

Question 1

What is the definition of supra glacial debris?

Answer 1

Transported on the surface of the glacier

Question 2

What is the definition of englacial debris?

Answer 2

Transported within the glacier

Question 3

What is the definition of sub glacial debris?

Answer 3

Transported at the base of the glacier

Question 4

What is extensional flow?

Answer 4

When ice flows over an increasingly steep gradient and experiences internal stress, resulting in crevasses

Question 5

What is compressional flow?

Answer 5

When ice flows over an increasingly decreasing gradient causing it to experienced internal stress, crevasses close

Question 6

What are glacial deposits?

Answer 6

Debris deposited directly by a glacier

Question 7

What are fluvio-glacial deposits?

Answer 7

Debris deposited by glacial meltwater

Question 8

What is the typical composition of glacial deposits?

Answer 8

Unsorted and unstratified

Question 9

What is Lodgement till?

Answer 9

This is formed subglacially and is plastered onto the underlying surface by the glacier above where friction between the debris and the bed is greater than the drag produced by the ice moving over it.

Question 10

What are the characteristics of Lodgement till?

Answer 10

It’s common where there is a large amount of subglacial debris or slow moving ice. It is often a mix of rounded boulders in a matrix of sand mud and clay due to the pressure involved. This still tends to be compacted and often forms drumlins.

Question 11

What is ablation till?

Answer 11

It is sometimes referred to melt-out till this material is deposited from sub to en to supra glacial debris due to the process of ablation

Question 12

What are the characteristics of ablation till?

Answer 12

It tends to be poorly compacted and sorted and unstratified. in some cases meltwater may remove some of the finer particles such as rock flour leaving only the larger ones. this is often more angular in nature than lodgement till that may have been dragged so glacially leading to a greater degree of rounding from abrasion.

Question 13

What is deformation till?

Answer 13

If a glacier read advances over an area of previously deposited till, the underlying till sediment can be folded or folded.

Question 14

What are the characteristics of deformation till?

Answer 14

Deformation till tend to be well compacted and contain many rock types. The patterns in the till will reflect the sheer stresses involved in formation.

Question 15

What is Moraine?

Answer 15

Moraine is an accumulation of glacial debris deposited by a glacier or left behind as the glacier retreats. Moraines can be categorised between either sub glacier or ice marginal ( formed on the edges)

Question 16

What is a till plain?

Answer 16

Glacier moraine can cover a large area of land producing an extensive relatively flat area known as a till plain

Question 17

What are the characteristics of till plains?

Answer 17

Till plains typically have 50 meter thickness of till (ground moraine), above which there may be other depositional landforms

Question 18

What is a Drumlin?

Answer 18

A drumlin is an elongated hill streamlined in the direction of ice flow and composed largely of glacial deposits. Most geographers agree that drumlins are composed of lodgement till.

Question 19

What is the size and scale of drumlins

Answer 19

They can measure up to 50 m to several kilometres in length, and a few metres to 100 m in height

Question 20

Where do drumlins form in relation to a glacier?

Answer 20

Drumlins form beneath the glacier (subglacial)

Question 21

What is the process called that forms the Drumlins in the subglacial sediment?

Answer 21

Subglacial sediment deformation– the moulding and sculpting of sediment by the flow of the glacier

Question 22

What are the current theories of Drumlin formation?

Answer 22

The fluvial theory and the deformational theory

Question 23

What is the fluvial theory of Drumlin formation?

Answer 23

The fluvial theory suggested that drumlin formation is due to subglacial meltwater flooding which deposits the fluvioglacial material. these deposits are then streamlined after the subglacial flood by the glacial ice with additional till to form the elongated mounds

Question 24

What is the deformational theory of Drumlin formation?

Answer 24

When a glacier moves over an obstacle at the base of the glacier, till is plastered around it. This happens when there is a large amount of subglacial debris. The lodgement till subsequently becomes streamlined into the elongated ‘teardrop’ shape as the glacier water flows over it. This theory is more widely accepted by geographers

Question 25

What is lateral moraine?

Answer 25

Lateral meine is found at the size of the glacier and is a product of freeze thaw weathering occurring on the side of mountains which loosens the rocks and causes rockfall onto the side of the glacier or it can be caused by mass movement for example an avalanche.

Question 26

What are the debris characteristics of lateral moraine?

Answer 26

The debris is more jagged and angular

Question 27

How is medial moraine formed?

Answer 27

It is formed when valley glaciers merge – the confluence of two valley glaciers (two lateral moraines merge)

Question 28

What are terminal moraines?

Answer 28

Terminal Moraines mark the furthest advance of a glacier. Debris is deposited at the furthest point at which the Glacier reaches.The Up-Valley side is usually steeper than the down-valley side. When formed by a valley glacier they tend to form a small crescent shaped ridge across the valley.

Question 29

What is a recessional moraine?

Answer 29

Recessional moraine are formed in exactly the same manner as a terminal Moraines but in this case, they represent a location where the glacier pauses for a considerable time during its retreat depositing ablation till. They are always found behind the terminal moraine.

Question 30

What are push moraines?

Answer 30

These form when a glacier advances over an existing moraine. The glacier will act as a bulldozer to push the moraine into a new ridge. This process will cause the clast in the moraine to orientate themselves vertically.

Question 31

What is meant by the sorting of rock?

Answer 31

The arrangement of rock fragments (clasts) into smaller sizes

Question 32

What is meant by the stratification of sediment?

Answer 32

The layering of similar size clasts

Question 33

What is meant by the shape of the sediment?

Answer 33

The degree of roundness of the clasts. Rounding of clasts occurs as a result of attrition, whereby during movement collisions occur removing the sharper edges.

Question 34

What are eskers?

Answer 34

Eskers are long sinuous (winding) ridges of sons, gravels and pebbles deposited by Mount water streams/rivers flowing through subglacial and sometimes on glacial, tunnels. They can be up to 20 m high, 3 km wide and 100 km long in extreme cases.

Question 35

How are Eskers formed?

Answer 35

-running water a high velocity due to hydrostatic pressure transports a large quantity of sediment which become rounded due to extensive attrition
-Fluctuating velocity due to seasonal variations in melt water enable deposition to occur with stratified layers of different size clasts
-Some theories suggest that the tunnel may become blocked, stopping the flow of water allowing rapid deposition
-A retreating glacier, then exposes the esker/landform deposit

Question 36

What is imbrication?

Answer 36

It is when the clasts align themselves in the direction of flowing water as the water will push on the flat face and flip them over so that they downstream

Question 37

What is a named example of an esker?

Answer 37

The Munro Esker near Munro Lake in northern Ontario formed from the retreat of the Laurentide ice sheet at the end of the Devensian, it is 250 km long and almost 5 km wide in places.

Question 38

How are Kames and Kame terraces formed?

Answer 38

They are formed supraglacially on the surface of the glacier. In the zone of ablation, surface melt water streams will pick up and transport super glacial debris – sands and gravels. These streams will flow into lakendepressions on the surface of the ice upon which the flow velocity will drop and the debris will be deposited. If the lake is at a glacier edge, a Kame Terrace will form, whereas away from the edge, a Kame will form. The ice then melts and the mound of debris is left behind leaving a Kame.

Question 39

Why will the clasts in Kames/Kame terraces be quite angular in shape?

Answer 39

They have not been eroded as they stay stationary/in the same place on the ice with limited to no attrition as it is wind blown or from avalanches

Question 40

Why do clasts on the Kames/ Kame terraces show clear sorting and stratification?

Answer 40

Meltwater drops heavier rocks first when it loses energy

Question 41

Explain why Kame terraces contain larger angular fragments

Answer 41

They’re more likely to occur on valley sides which are prone to mass movement – avalanches and rock falls on the ice margin

Question 42

What is a named example of Kames and Kame terraces?

Answer 42

The east Lothian area of Scotland contains many Kames and Kame terraces. These features are typically up to 20 m high and 200 m in length and were formed during the retreat of the ice at the end of the Devensian glaciation

Question 43

What are kettle holes and kettle hole lakes?

Answer 43

Kettle holes are depressions found in the outwash plane (sandur) located in front of a retreating glacier. When these depressions are filled with water they are called Kettle-hole Lakes. They form where blocks of stagnant or dead ice calve from the front of the glacier.

Question 44

How are kettle holes formed?

Answer 44

-Blocks of ice are left behind by the retreating glacier
-Sediment is shed from retreating glacier and buries the ice blocks
-Ice blocks melt away and the sediment collapses forming depressions
-Groundwater sometimes fills the kettles if the water table is high enough or the hole is deep enough , they can also be filled with rainwater dependent on the mix of sediment if it is permeable or impermeable

Question 45

What is a named example of kettle holes and kettle lakes?

Answer 45

The Meres of North Shropshire, there were formed at the end of the Devensian glaciation when the ice sheet retreated. Hundreds of small Kettle Hole depressions and lakes were formed. This area also contains some particularly large Kettle-hole lakes such as The Mere, Cole Mere and White Mere, which are over 300 m across.

Question 46

What are pro glacial lakes?

Answer 46

They are found in front of a retreating glacier when melt water streams will cause lakes to form in depressions in front of the glacier or wear a recessional Moraines dam the melt water. These pro glacial or ice margin lakes will fill with sediment as the stream velocity will slow upon entering the Still water of the lake.

Question 47

What is a varve?

Answer 47

Above is the alternating annual layers of fine clay/silt and coarser sand/gravel from the sediment that begins to fill the lakes.
Coarse sand/gravel layers are formed in the summer/spring due to the high rates of ablation causing more water meaning that the streams will have more energy
Fine silt/clay layers are formed in the winter as they are suspended in the water and settle due to less energy because of less melt water

Question 48

How are Varves used?

Answer 48

They can be useful to geographers in the UK as the layers can give them an idea how long it took the glaciers in the UK to retreat completely – age of Lake

Question 49

What is a sandur (outwash plains)?

Answer 49

The flat landscape formed by Fluvioglacial deposition in front of the retreating ice sheet is known as a sandur or outwash plain. These landscapes are dominantly composed of sand and gravel deposited by flowing water, but may also contain other fluvioglacial landforms.

Question 50

What is an example of an outwash plain?

Answer 50

Some of the most impressive sandur/outwash plains can be found in Iceland such as Skeidararsandur covering 1300 km² – the largest sandur in the world