Glaciated Landforms A-level Geography

What was the last ice age called?
When was it?

Pleistocene ice age. It occurred , 2 million to 11,700 years ago

Name the last glacial period that led to glaciers in the Lake District.
How long was it?

Devensian Glacial.
It lasted from around 70,000 years BP to about 11,000 years BP, peaking 18,000 years ago

Zone of accumulation

High altitude area where snow accumulation exceeds ablation

Equilibrium line

Altitude where snow accumulation equals ablation

Zone of ablation

Low altitude area where ablation exceeds snow accumulation

Glacier mass balance

Difference between accumulation and ablation in a glacier over a year

Positive mass balance

When accumulation exceeds ablation in a glacier system over a 1 year period

Negative mass balance

When ablation exceeds accumulation in a glacier system over a 1 year period

Why are glaciated landscapes considered to be systems? Are they open or closed systems?

Complex systems with inputs (snow, energy), processes (abrasion, deposition), stores, and outputs (meltwater, debris).

They are open systems with energy and matter exchange

Process where snow transforms into glacial ice is called ___

Diagenesis

3 characteristics of Warm based glaciers-

Found at high altitudes, meet pressure melting point, move faster, erode more

3 characteristics of Cold based glaciers-

Located at high latitudes, frozen at base, move slowly, erode less

What is the main movement process for warm based glacier?
What 3 processes make it up?

Basal sliding - involving slippage, regelation, and substrate deformation

What is the main movement process for cold based glacier?
What 2 processes make it up?

Internal deformation. Involves intergranular slip and laminar flow

Define the term "Geomorphic processes".
What are the 5 categories?

Geomorphic processes are natural processes which change the shape of the glaciated landscape. The 5 categories are:
- Weathering
- Mass movement
- Erosion
- Transportation
- Deposition

Define Nivation

Process combining freeze-thaw weathering, solifluction, transportation, and chemical weathering, enlarging hillside hollows

Valley glacier case study is....

Lake District

Ice sheet case study is...

Laurentide Ice Sheet

Corries. Give a.....
- Definition
- Named examples
- Location
- Scale

Definition: An armchair shaped hollow which tend to form on the N and NE face of a mountain
Name: Red Tarn
Location: Helvellyn region of the Lake District
Size: 300m high back wall, about 720m above sea level

THREE most influential geomorphic processes in the formation of a corrie.

Plucking - steepens the backwall and provides debris for abrasion.

Abrasion - deepens the floor of the corrie. Plucking provides subglacial debris contributing to high rates of abrasion.

Rotational movement - deepens the hollow and forms the rock lip.

Aretes. Give a:
- Definition
- Named examples
- Location
- Scale

Definition: A knife edge ridge between 2 corries
Name: Striding Edge
Location: Between 2 corries - Red Tarn and Nethermost Cove
Size: 200-300m high slopes and about 1km long

Pyramidal Peak, give a:
- Definition
- Named examples
- Location
- Scale

Definition: A pyramid shaped peak formed when 3 or more corries erode backwards
Name: Matterhorn
Location: Switzerland
Size: Peak is over 1,200m high

Glacial trough, give a:
- Definition
- Named examples
- Location
- Scale

Definition: A U shaped valley with steep sides and a flat valley base formed as a glacier flows down a previous V shaped river valley.
Name: Patterdale
Location: Helvellyn region of the Lake District
Size: 13km, with a flat wide valley bottom (2km wide) and steep sides 200 -300 m high

Name additional features found in a glacial trough (5 possible answers)

- Hanging Valleys e.g Glenridding Beck
- Truncated Spurs
- Rock Basins and bars
- Misfit streams
- Ribbon Lakes e.g. Ullswater (11km long)

THREE most influential geomorphic processes in the formation of a glacial trough

- Erosion - Abrasion and plucking deepen & widen the valley into a U- shape.
- Glacial movement -Basal sliding allows the glacier to move and causes abrasion.
- Weathering - FTW takes place on the slopes above the glacier which provides debris which the glacier will use to erode.

Roche Moutonnee, give a:
- Definition
- Named examples
- Location
- Scale

Definition: A mass of resistant rock found on the floor of the glacial trough. Eroded by the glacier to create a smooth stoss end and jagged steep lee side
Named example: Norfolk Island
Location: In Ullswater, Lake District
Scale: area of 1000m2

Name 3 types of energy in a glaciated landscape.

Gravitational potential, kinetic, and thermal energy

THREE most influential geomorphic processes in the formation of a roche moutonne

Erosion - abrasion on stoss side smooths and. Plucking on the lee slope causes this end to be steeper and jagged

Weathering - pressure release and FTW on the lee slope weakens the rock and encourages plucking

Glacial movement - Ice is able to deform due to local pressure melting and flow around the obstacle via regelation.

Moraine, give a:
- Definition
- Named examples from the Lake District
- Location

Definition: Ridges of glacial till found in the floor of a glacial trough.
Named examples from the Lake District: Hummoky moraine in Glenridding Beck and end moraine at Red Tarn
Location: Hellvelyn region of the Lake District

Compare the locations of terminal, recessional and lateral moraine

Terminal moraine - arc shaped ridge going from one side of the valley to another marking the maximum extent of the glacier.

The ridge is steeper on the up valley side
Recessional moraine - parallel to the terminal moraine and with the same shape but further up the valley

Lateral moraine - ridge of glacial till running parallel to the valley sides

Describe the 4 characteristics of glacial till

Unsorted, unstratified, angular, non-orientated

THREE most influential geomorphic processes in the formation of a moraine

Deposition - They are landforms of depostion

Transportation - The glacier acts as a giant conveyor belt transporting material to its snout. ​

Erosion - material from plucking and abrasion adds to debris which the glacier will deposit.​

Till sheet

Large flat area of unsorted glacial till

Drumlins, give a:
- Definition
- Named examples
- Location
- Scale

Definition: A streamlined hill composed of subglacial sediment
Named examples: Vale of Eden drumlin swarm
Location: Vale of Eden Cumbria
Scale: 308 drumlins covering a 36Km2 area. Each one ranges from 150-1000m long and 75-500m wide.

How does a drumlin form

In zones of ablation the glacier loses competence and deposits subglacial debris. As the glacier continues to move forward it moulds the debris into streamline shaped mounds of glacial till with a steep stoss end and gentle tapered lee slope

THREE most influential geomorphic processes in the formation of a drumlins

Deposition - these are landforms of deposition
Erosion - plucking and abrasion adds to debris which the glacier will transport and later deposit. ​
Glacial movement - It acts as a giant conveyor belt transporting material to its snout.

What is meltwater flowing ON a glacier called?

Supraglacial streams

What is meltwater flowing THROUGH a glacier called?

Englacial streams

What is meltwater flowing BELOW a glacier called?

Subglacial streams

What is meltwater flowing BEYOND a glacier called?

Proglacial streams

whats pressure do englacial and subglacial streams experience?

They flow under hydrostatic pressure- very high pressure. When meltwater exits the glacier it experiences friction due to a loss in this pressure.

How does meltwater differ diurnaly?

More discharge during day when its warmer

How may sediment show its graciofluvial?

-stratified, small particles dropped in winter with low discharge, large dropped in summer

-graded

-smooth

-sorted

Whats is an Outwash Plain?

A flat expanse of glaciofluvial sediment located in the proglacial area

Example of an outwash plain:

Solheimajokull, Iceland

Area= 57km²

Formation of an Outwash Plain:

Melting occurs at glacier snout creating meltwater streams. Streams carry debris away from glacier and as friction build up, it begins to be deposited. Heaviest material is dropped first them finer material the further along. As glacier retreats the point of deposition retreats.

Kettle holes-

Stagnant dead ice slowly melt, it begins to be buried by outwash material, once melted the overlying sediment forms depressions in the outwash plains.

Why do meltwater streams braid?

Deposited material create mid-channel bars/ eyots in the way of meltwater streams so as they move around, the streams will braid.

Effects of plant colonisation:

Biological weathering- plant colonisation, roots break apart the rocks

Erosion- material becomes more stabilised/ less prone to erosion

Aeolian processes- more stable so less likely to be eroded by wind

What is an Esker?

A long, sinuous ridge composed of stratified sand and gravel deposited by meltwater streams. Shows the path of glacial retreat.

Example of an esker:

Mosedale Esker, Lake District

200m long, 50m wide, 5m tall

Formation of an Esker-

Subglacial meltwater streams carry glacial debris. Streams no longer flow under hydrostatic pressure they did in the glacier so friction begins to increase. Material is deposited alongside the meltwater streams and causes ridges to build up- an Esker. As glacier retreats, point of deposition also does so Esker grows in length. Eskers become beaded if speed of retreat differs.

What is a Kame?

a hill or hummock of stratified sand and gravel laid down by a glacial meltwater (supraglacial streams)

Formation of a Kame:

Temp increase causes supraglacial streams to form leading to the creation of a proglacial lake. Stream carries debris which deposits at the end of the glacier in a sorted pattern, Kame grows outwards into progladial lake, glacier retreats.