Glaciation EQ3 Flashcards
(27 cards)
What are the processes of glacial deposition?
- Lodgement till
- Ablation till
- Flow till
Glacial deposition - What is lodgement till?
Beneath glacier, lodged in the bed and generally occurs when debris load is high and erosion ability of is reduced
Characteristics - more rounded less angular, elongated and orientated to flow of ice
Glacial deposition - What is ablation till?
Melting of ice occurs around debris, sub/supraglacially along margins of glacier, debris carried into ablation zone and deposited
Characteristics - more angular less altered by abrasion, less spherical
Glacial deposition - What is flow till?
If high meltwater exists it means material will slide during deposition, act like liquid, usually supraglacially
Characteristics - more angular less spherical, show evidence of sorting
What is a cirque/corrie?
Snow accumulates in a hollow, builds up and compresses to ice.
Freeze-thaw and plucking of back wall causes it to steepen, abrasion deepens. Ice then melts causing a lake.
What is a hanging valley?
The main glacier has eroded a trough deeper and wider than smaller glaciers joining it. Then it retreats leaving large trough with many hanging valleys along the side.
What is an arete?
It is 2 corries formed side by side.
What is a ribbon lake?
After de-glaciation, water fills hollows within the glacial trough.
What is a U-shaped valley?
This is when a glacier has carved through pre-glacial mountain, straightening, widening, deepening.
What is a truncated spur?
When inter locking spurs are widened by glacier abrasion and some plucking
What is a pyramidal peak?
3+ corries erode a mountain
What are Roche mountonnees?
They are formed beneath warm-based ice with abundant meltwater due to abrasion on stoss, plucking on lee
What is crag and tail?
A hill with a tail of softer rock, selective erosion and deposition beneath ice sheet, hill or crag is usually strong rock resistant glacial erosion.
What are whale backs?
formed beneath relatively thick, warm ice, little meltwater no basal cavaties
what is stoss and lee?
stoss - upstream
lee - downstream
What are striations?
Scratches in bedrock caused by ice dragging debris across the surface.
What are chatter marks?
A series of often cresent - shaped gauges chipped out of bedrock, glacier moves and drags rock fragments underneath and stick causing irregular chips and fractures.
What are cresentic gauges?
Concave and stoss features caused just like chatter marks however have a far more regular cresentic pattern.
What are the glacial sub-ariel processes?
- Meltwater erosion
- Solution
- Block weathering
-Freeze thaw
- What are the types of ice-marginal morraines?
- Terminal - marks max extent of advancement and found at the snout of glacier
- Medial - found in the centre of a glacier when 2 lateral moraines join together
- Lateral - material derived from freeze thaw at the valley sides and carried at the side of glacier.
- What are the types of ice-marginal morraines?
- Recessional - form behind terminal morraines and mark stages of glacier retreat when it remained stationary long enough for material to build up
- Hummocky - thought to form when ice thins and material is deposited.
What is a Drumlin (sub-glacial morraine)?
They consist of lodgement till, till is moulded into streamlined mounds called drumlins. The steeper, more blunt end is the stoss end.
Glacial debris
Debris underneath ice is called till and can be transported hundreds of miles.
What is an ice-contact feature?
Landforms created by the direct deposition of glacial debris (till) from ice, rather than meltwater, not sorted and stratified.
