Glacial Landscapes Flashcards
What are the three types of glacial landform?
- Depositional
- Erosional
- Fluvioglacial
What are the erosional landforms?
Roche Moutonnée
U-shaped valley
Truncated Spur
Hanging Valley
Crag and Tail
Corrie
Arête
Ribbon Lake
Tarn
Pyramidal peak
How can we categorise erosional landforms?
Macro
Meso
Micro
What are the macro erosional landforms?
Corrie
Arête
Pyramidal Peak
U-shaped valley
Ribbon lake
Hanging valley
Truncated spurs
What are the meso erosional landforms?
Roche Moutonnée
Crag and Tail
What are the micro erosional landforms?
Striations
What are the depositional landforms?
Moraines
Drumlins
Erratics
Till Plains
What is moraine?
The accumulation of unsorted debris (till) deposited directly by a glacier as it advances and retreats
What is till?
Unstratified (no layers) and unsorted sediment containing a mix of rock particles (clay, sand, gravel, boulders) deposited by a glacier
What are the six different types of moraine?
- Lateral
- Medial
- Terminal
- Ground
- Recessional
- Push
Where are the different types of moraine found?
- LATERAL
- sides - MEDIAL
- middle of two merging - TERMINAL
- end - GROUND
- underneath - RECESSIONAL/PUSH
- behind terminal moraine, marking stages of glacial retreat and/or readvancement
How is lateral moraine formed?
Debris falling from the cliffs at the side of the glacier due to freeze-thaw action gets trapped at the edges and transported as the glacier moves
How is medial moraine formed?
When the lateral moraines of two converging glaciers join together
How is terminal moraine formed?
When the debris pushed at the glaciers snout is deposited as a ridge when the glacier reaches its maximum extent and begins to retreat
How is ground moraine formed?
As the glacier moves it deposits a thin irregular layer of till at its base
How is recessional moraine formed?
When a retreating glacier temporarily stabilises, depositing a ridge of debris before continuing to melt back
How is push moraine formed?
If the glacier advances again after retreating then ridges of sediment previously deposited get shoved up into little hills
What does recessional/push moraine look like?
A series of ridges behind the terminal moraine, showing pauses in the glaciers retreat.
Can show folding/faulting/tilting due to the force of the glacier moving forward
Often curved and perpendicular to the direction of the glaciers advancement
What are drumlins?
Give an example
Elongated, egg-shaped hills made of till formed when a glacier moving over an obstruction deposits and shapes till over the to of it
e.g. The Drumlin Field beneath Cam Fell, Yorkshire Dales
What are eratics?
Give an example
large, random rocks transported by glaciers hundreds, sometimes thousands of km from where they originate. They do not fit with the size or type of rocks in the area in where they are deposited
e.g. The Great Stone of Fourstones, moors of Tatham Fell, England
What is a glacial outwash plain?
Give an example
Where till is carried and deposited by meltwater streams in layers further down the valley from the glacier snout
e.g. Lake Clarke National Monument, Alaska
What is another name for a glacial outwash plain?
Sandur
What is outwash?
Sediment that has been transported away from a glacier by meltwater
Why do you get layering in the outwash plain?
changing competence over time:
- bigger stuff is deposited in summer due to more meltwater = large sediment, high competence
- smaller stuff is deposited in winter due to less meltwater = small sediment, low competence
How do glacial outwash plains form?
- During summer, temps increase, melting increases, and sediment is deposited on the valley floor or sides of a moving glacier
- Meltwater will flow out of the glacier snout, forming meltwater rivers
- Meltwater rivers carry large amounts of glacial till, which undergoes erosion (attrition) to become outwash
- The finer till is then sorted, and when the energy of the river reduces, the outwash is sorted and deposited as layers further down the valley on the outwash plain
What and where are the different zones on a glacial outwash plain?
PROXIMAL ZONE
- close to the snout, just beyond the terminal moraine
MEDIAL ZONE
- the large middle majority of the outwash plain
DISTAL ZONE
- the end of the outwash plain, furthest away from the snout of the glacier
What is a Roche Moutonnée?
Give an example
A bedrock bump that has a steep and jagged face on the lee side due to plucking, and a smoothed/polished face on the stoss side due to abrasion
e.g. Dulnain Bridge, Cairngorms NP
What is a U-shaped valley?
Give an example
A v-shaped valley that has been widened, deepened and straightened by the movement of a glacier. They have steep sides and a flat floor
e.g. Ullswater Valley
What is a hanging valley?
Give an example
Where a tributary valley is left suspended above the main valley floor due to different rates of erosion between it and the main valley
e.g. Cwm Dyli, Eryri NP
What is a truncated spur?
Give an example
A steep cliff face either side of a glacial trough caused by the glacier truncating/cutting off spurs as it moves down the valley. An inverted V shape
e.g. Nant Ffrancon Valley, Eryri NP
What is a crag and tail?
Give an example
Where a glacier travelling over a piece of resistance rock with soft rock on both sides creates a small rocky hill from which there extends a tapering ridge of unconsolidated debris
e.g. Edinburgh - Castle is on the Crag, The Royal Mile is the Tail
e.g. North Berwick
What is an arête?
Give an example
A knife edge ridge formed when two corries form back to back
e.g. Striding Edge, Helvellyn
What is a pyramidal peak?
Give an example
An angular, sharply pointed mountain summit/peak formed when three or more corries form back to back
e.g. the Matterhorn
What is a ribbon lake?
Give an example
When the glacier travels over softer rock is can carve a deeper trough in these areas, which will ill with water when the ice melts
The harder rock left behind are called rock steps
e.g. Windermere
What is a tarn?
Give an example
When the hollow in the bottom of a corrie fills with water when the ice in the corrie melts which doesn’t flow out due to the corrie lip
e.g. Red Tarn, Helvellyn
What factors affect the rate and amount of abrasion?
- meltwater
- debris
- mass of glacier
- ice thickness
- velocity
- gradient
- thermal regime
Geology: - relative hardness (type of rock)
- jointing
- permeability
What are the two categories of fluvioglacial landforms?
Ice contact
Pro glacial
What are the fluvioglacial ice contact landforms?
Eskers
Kames
Kame terraces
What processes does glacial meltwater impact on?
movement
erosion
entrainment
transport
deposition
Where does meltwater come from?
Surface
Basal (PMP)
Where does glacial meltwater flow when it is on the glacier?
Subglacial
Englacial
Proglacial
Supraglacial - moulins and streams
What is a moulin?
a roughly circular and vertical/near vertical well-like shaft in a glacier formed when surface meltwater exploits a weakness in the ice
What are the fluvioglacial processes?
EROSION
- sub glacial, proglacial
TRANSPORT
- competence
DEPOSITION
- ice contact, pro glacial
What is competence?
the ability of water to transport material
What is high competence?
What is low competence?
high speed
high volume
high discharge
low speed
low volume
low discharge
What are the characteristics of fluvioglacial deposits?
Rounded
Sorted
Stratified
Why are fluvioglacial deposits rounded?
because of attrition in the water - rocks crash into each other and knock corner off
Why are fluvioglacial deposits sorted?
because of the changing competence of the water - larger sediment is deposited first as the water flow slows
Why are fluvioglacial deposits stratified?
because you get daily/seasonal changes on a regular basis, leading to layers on layers
What is a kame?
Give an example
a mound of sorted/stratified sand and gravel found on the glacial valley floor or in the outwash plain
e.g. Holy Hill, Wisconsin
What are the three different types of kame?
Kame delta
Crevasse kame
Kame terrace
What is a kame delta?
Where the meltwater stream flowing round the sides of a glacier is dammed by a terminal moraine, and so the kame forms in a proglacial lake
What is a crevasse kame?
small hummocks of glacial surface-deposited sediments that have been left behind
What is a kame terrace?
Give an example
piles of debris left by meltwater channels that have been deposited between the sides of the valley and the glacier
e.g. Carstairs kames, Scotland
What is the difference between a kame and moraine?
KAME:
- sorted
- stratified
(heaviest gravel at base, finer sediment on top)
- fluvioglacial deposition
MORAINE:
- unsorted
- unstratified
(no water competence involved)
- glacial deposition
BOTH:
- deposition
- form anywhere round the glacier
What is an esker?
Give an example
a long, winding ridge composed of stratified sand and gravel (sediment) deposited by subglacial meltwater streams in tunnels, running parallel to the flow of the glacier
ONLY in a stagnant glacier/meltwater stream
e.g. Denali Highway Esker, Alaska
Why does a glacier/meltwater stream have to be stagnant for an esker to form?
if it moved, it would transport material not deposit it
Give some esker stats
20-30m high
a few (days/weeks formation) - 100s (100s-1000s year formation) km
50-500m wide
Can be:
- triangular
- semi circular
- multi crested
- flat topped
Types:
- single channel
- tributary channel
- continuous
- non continuous
What is the difference between an esker and moraine?
ESKER:
- forms in outwash plain only
- stratified
- fluvioglacial deposition
MORAINE:
- forms all round the glacier
- unstratified
- glacial deposition
BOTH:
- deposition
- sand and gravel
What is the importance of eskers?
- sand and gravel used for construction
- roads built on them e.g. Denali Highway
- used in hunt for diamonds
- ecology - plants grow on the e.g. cranberries
What are the fluvioglacial pro glacial landforms?
Kettle holes/lakes
Varves
Glacial outwash plains
What is a kettle hole?
What is a kettle lake?
Give an example
A depression or hole in an outwash plain formed by a retreating glacier
A kettle lake is when the ice melts and the kettle hole fills with water
e.g. Ellesmere, Shropshire
What is a varve?
Give an example
stratified, distinct annual layers of sediment found in the deposits at the bottom of a pro glacial lake. 2 layers, one sandy, light coloured one, and one darker silt.
e.g. in Lake Suigetsu, Japan
What forms the 2 distinct layers in a varve?
SEASONALITY: In summer, discharge is high so the coarse sediment is deposited, and in winter, discharge is low so the finer sediment is deposited
Why are varves important to humans?
paleoclimatic indicators, radiocarbon dating, helps us understand climate change
e.g. in Lake Suigetsu, there are thousands of annual layers dating 50,000 years
