10 Glaciation Flashcards
Epoch
Subdivision of a geological period ranging from 1-10mil years
Cold periods of temp variations were called…
Glacials
Warm periods of temp variations were called…
Interglacials
Nunatak definition
Part of the landscape protruding above ice cover
Terminal Moraine definition
Material deposited in front of the ice sheets when the ice had reached its maximum advance
Glacial ice formation:
Ice advance-ice retreat
snow accumulates
weight compresses air from underlying layers into
1.granular ice
2.firn
3.glacial ice.
Low air concentration=bluer ice
Where can valley glaciers b found
The Alps
Where can ice sheets be found
Greenland
What is glacier mass balance
Difference between the amount of ice a glacier gains in winter and loses in summer
Explaine positive mass balance
Glacier gains more ice in winter than it loses in summer = advancing
Explain negative mass balance
Glacier loses more ice and is retreating
What dors it mean when a glacier is labeled as “stationary”
When loss and gain of ice are balanced
What are the two zones glaciers have called?
Accumulation zone
Ablation zone
What is the accumulation zone of a glacier?
Snow falls and remains all year here
What is the ablation zone of a glacier?
Winter snow melts during the summer here
What divides the accumulation and ablation zones of a glacier
Snowline
Define ablation
Loss of ice and snow from a glacier by melting,runoff and evaporation
Name three ice flow processes
1.Basal Sliding
2.Plastic Flow/Internal Flow
3.Rate of flow
Explain 1.Basal Sliding
At base of glacier friction from heavy ice on bedrock causes melting.
Meltwater acts as lubricant and causes glacier to move downhill
Rate of this will depend on steepness of glacier and rate of ice accumulation
Explain 2.Plastic flow/Internal flow
2 zones WITHIN a glacier
Upper zone:Ice brittle. breaks easily to form crevasses
Lower zone: ice under steady pressure=stronger wnd able to bend without breaking
Explain 3.Rate of flow
Friction with bedrock and valley sides means rate of flow at base and sides is much slower than at surface(middle)
In middle surface glacier ice flows faster
name 3 forms of glacial erosion
1.Plucking
2.Abrasion
3.Freeze-thaw action
Explain 1.Plucking
Plucking is when glacier ice melts and seeps around a rock, refreezes and carries the rock with the glacier as the glacier moves
Explain 2.Abrasion
The rock particles on the base of the glacier abrade the rock underneath the glacier leaving marks called STRIAE on the rock.
Explain 3.Freeze thaw action
When water seeps into cracks in the rock and refreezes it expands and can break off rock around the crack called scree
Name the two types of glaciation
1.Upland Glaciation (alpine)
2.Lowland Glaciation (continental)
What is Upland Glaciation
Mountainous regions
Carried out by glaciers
Mostly landforms of erosion
Alps/Himalayas/Kerry
What is Lowland Glaciation
Carried out by ice sheets
Mostly landforms of deposition
Greenland/Kildare/Offaly
What is the rate of glacial erosion influenced by
Presence/absence of well jointed bedrock
Gradient (steeper=faster erosion overall)
Shape Size and amount of Basal Debris
Describe a cirque
Armchair shaped depression that forms on slopes of upland areas
Describe an Arête
2cirques form back to back creating a narrow ridge in the middle called an arete
Describe a pyramidal peak
Angular pointed mountain peak
describe a U shaped valley
Valley with steep sides and a broad flat floor
Describe pater noster lakes
Series of glacial lakes connected by streams
