5.3: The glacier landform system Flashcards
Name the 5 process’s of glacial erosion
- Abrasion
- Plucking
- Fracture and Traction
- Dilation
- Meltwater erosion
How does abrasion contribute to glacial erosion?
What features does it create
Abrasion by individual clasts (stones) which leads to micro-features such as striations and chatter marks. Additionally rock flour (size under 0.1mm in diameter) polishes the underlying rocks by ‘sandpaper’ action
How does Plucking contribute to glacial erosion?
A type of erosion where melt water in the glacier freezes onto rocks, and as the ice moves forward it plucks or pulls out large pieces along the rock joints.
How does Fracture and Traction contribute to glacial erosion?
Occurs as a result of the crushing effect of the weight of moving ice passing over the rock and variations in pressure lead to freezing and thawing of the meltwater (basal melting) which aids the plucking process
How does Dilation contribute to glacial erosion?
where the variable weight of glacier ice on top of bedrock can cause fractures to open up, expand and extend deeper.
How does Meltwater Erosion contribute to glacial erosion?
What are the 2 parts to it?
Can be both mechanical (similar to fluvial erosion) and chemical, whereby the glacial meltwater dissolve minerals and carry away the solutes, especially in limestone rocks
Define Glacial debris entertainment
State the 2 ways it can occur in your answer
Entrainment is the incorporation of debris on to or into the glacier from supraglacial or subglacial sources
State where debris will come from if it is Supraglacial debris entertainment
Sources include
1. material falling from hillsides
2. material being washed or blown onto the glacier
3. atmospheric fall out like volcanic ash (often seen in iceland)
State where debris will come from if it is
Subglacial debris entertainment
Sources include
1. material eroded from the glazier bed and valley walls
2. material frozen to the base from subglacial streams
3. englacial material that has worked its way through the glacier or ice sheet
For ice sheets most debris is transported …? via the basal layer
subglacially
For …? glaciers there is more transport by englacial and supraglacial debris as a result of more frequent contact at their …? margins.
- valley
- lateral
As rocks are transported they come into …? with each other and are ground down (comminuted) by a process similar to river …?
- contact
- attrition
Glacial sediment transportation occurs horizontally and ..? through glaciers, through the movement of the ice itself, …? transporting sediment through the glacier drainage system or by glacial …? of sediments.
- vertically
- meltwater
- deformation
What happens during glacial deposition?
It occurs when material is released from the ice at the margin or the base of a glacier
Name 2 deposition mechanisms
Deposition mechanisms include;
- release of debris by melting or sublimation
- lodgement of debris by friction
- deposition of material from melt water
- the disturbance and remodelling of previously deposited sediments
Deposition may occur directly on the …? or sediment may be released into …?
- ground
- meltwater
What size feature constitutes a Macro-scale feature
Macroscale features of glacial erosion are those features that are 1 km or greater in dimension
What size feature constitutes a Meso-scale feature
Mesoscale features of glacial erosion are those between 1m and 1 km in size
What size feature constitutes a Micro-scale feature
Microscale landforms of glacial erosion are generally less than 1m in size
Name 3 macro-scale features
- knock and lochan landscapes
- cirques
- aretes and pyramidal peaks
- glacial troughs
- ribbon lakes
- till plains
- terminal moraines
- sandurs
Name 3 meso-scale features
- Criag and tail
- roches moutonnees
- drumlins
- kames
- eskers and kame terraces
- kettle holes
Name 3 micro-scale features
- striations
- glacial grooves and chatter marks
- erratics
