Glaciation EQ 2 Flashcards
(26 cards)
What is the ablation zone?
The glaciers outputs: meltwater, rivers, calving
What is the accumulation zone?
The glacier inputs: snowfall, avalanches, rain
What is the zone of equilibrium?
This is the balance between accumulation and ablation and can move depending on: rate of accumulation or ablation (greater than rates) and time of year.
Movement - what is basal sliding?
Meltwater beneath the glacier acting as a lubricant so glaciers can move.
Movement - What is creep and regulation?
Occurs when glacier moves over an obstacle greater than 1m wide, pressure decreases PMP and causes meltwater to form, lubricant.
Movement - What is internal deformation?
Individual ice crystals slip and slide over eachother, crystals become fractured due to intense pressure, ice deforms and moves downhill.
What is a crevasse?
Cracks that form in glacier ice when the glacier is put under too much stress and can also be caused by ice flowing over bumps or steps.
What are the types of crevasse?
-Bergschunds
-Transverse
-Marginal and radial
-Longitudinal or splay
Crevasse - What is a Bergschrund?
These form at the beginning of a glacier where the glacier pulls away from the rock wall.
Crevasse - What is a longitudinal?
These form in the direction of glacier flow, ice spreads out sideways to cover a large area.
Crevasse - What is a marginal?
These form near the side and is caused by friction between the valley wall and glacier and form where a glacier turns a corner.
Crevasse - What is a transverse?
These form across a glacier where speed increases and they fan across the glacier. There are common in accumulation zones near steepening zones.
What is subglacial bed deformation?
When glaciers flow over soft sediment and results in being ground down and increased speed.
What are the factors affecting the velocity of the glacier?
Altitude - affects the mass balance
Gravity/gradient - the steeper = the faster
Size - the heavier = more force needed to move
Friction - when in contact with the ground there is friction, must overcome to move
What are the factors effecting rates of erosion?
-Ice thickness - greater pressure = increased movement
-Precipitation levels - higher snowfall = greater accumulation, more weight
-Rates of ablation - more meltwater increases basal sliding
-Bedrock permability - meltwater can percolate away, slower, soft rock = faster
-Ice slope and gradient - steeper the angle, faster the movement
-Ice temperature - colder ice moves slower than warmer ice
What are the 4 glacial processes?
Erosion, entrainment, transport, deposition
What is erosion?
The removal of material via plucking, abrasion, fracture and dilation
What is entrainment?
Small rock fragments are trapped by basal ice freezing around them which then pulls them along
What is transport?
Rock debris is transported on the surface (supraglacial) within the ice (englacial) and at the base (subglacial).
What is deposition?
Glacial till (sediment deposited by the glacier ice) Fluvio-glacial debris is deposited by glacial meltwater.
What are the macro-scale (1km+) features?
-Cirque/corrie
-Arete
-Hanging valley
-Ribbon lake
-U-shaped valley
-Truncated spur
-Pyramidal peak
What are the meso scale (10m-1km) features?
-Stoss and Lee
-Whale backs
-Roche mountonnees
-Crag and tail
-Knock an lochan
What are micro scale (few metres or less) features?
- Striations
- Chatter marks
- Cresentic gauges
What are cresentic gauges?
Concave and stoss features caused just like chatter marks however have a far more regular cresentic pattern.
