glaciers Flashcards
what are glaciers?
Thick masses of recrystallized ice
how much of the earth do glaciers cover?
10%
how much of the earth did glaciers cover during ice ages?
30%
what are characteristics of glaciers?
Last all year long
* Flow via gravity
* Mountain and continental
how do glaciers form?
snowfall accumulates
snow is turned into ice
how is snow turned into ice?
Snow is buried by later falls
* Compression reduces volume
* Burial pressure causes melting and recrystallization
* Snow turns into granular firn
* Over time, firn becomes interlocking crystals of ice
what are three conditions required for glacier formation?
Cold local climate (polar latitudes or high elevation)
* Snow must be abundant; more snow must fall than melts
* Snow must not be removed by avalanches or wind
what are the two categories of glacier?
Alpine (mountain)
Continental (Ice sheets)
what are the types of alpine glaciers?
Cirque glaciers
valley glaciers
ice caps
piedmont glaciers
what are cirque glaciers?
fill mountain top bowls
what are valley glaciers?
flow like rivers down valleys
what are ice caps?
cover peaks and ridges
what are piedmont glaciers?
spread out at the end of a valley
how do alpine glaciers flow?
from high to low elevation
what are continental glaciers?
Vast ice sheets covering large land areas
how do continental glaciers flow?
outward from the thickest part of the sheet
what are the two main continental glaciers?
Greenland
Antarctica
what is albedo?
The amount of light or radiation reflected by a surface.
can glaciers be stationary?
no
3 conditions needed to form a glacier?
A cold local climate, abundant snow, and no snow removal by wind or avalanches.
what are the two ways glaciers move?
Basal sliding and plastic deformation
what is basal sliding?
The process of a glacier sliding due to meltwater at the base of a glacier.
why does plastic deformation occur?
Ice cannot crack at certain pressure, so it will bend/fold.
What forms at the surface of glaciers when it undergoes plastic deformation?
Crevasses because the upper zone is too brittle to flow.
Why do glaciers move?
The pull of gravity is strong enough to make glaciers constantly flow.
What depth can ice not crack at?
60m
Why do glaciers move?
The pull of gravity is strong enough to make glaciers constantly flow.
Why do continental glaciers move?
Ice spreads away from the centre of accumulation because the ice sheet is always thicker in the middle.
What is the rate of glacial flow controlled by? (3 things)
The severity of slope angle,
amount of basal water,
the location of ice on the glacier.
What is the zone of accumulation?
The area of net snow accumulation
What is the zone of ablation?
The area of net ice loss.
Where do the zones of accumulation and ablation meet?
The equilibrium line
What does the equilibrium line help determine?
If a glacier is retreating or advancing downhill, however it is always moving down
What is the toe of a glacier?
The leading edge of the glacier
What happens if the amount of accumulation is equal to the amount of ablation?
The glacial toe stays in the same place (glacier gets thicker).
What happens if the amount of accumulation > amount of ablation?
The glacial toe moves forward.
What happens if the amount of accumulation < amount of ablation?
The glacial toe retreats upslope and the glacier gets thicker, but it’s still moving down.
What force acts on glaciers flowing out over ocean water? What force no longer does?
Depositional forces still act in the form of drop stones, but no more erosion force.
what are tidewater glaciers?
Valley glaciers entering the sea.
what are ice shelves?
Continental glaciers entering the sea.
What is sea ice? What does it require?
Non-glacial ice formed of frozen seawater. It requires crystallization.
How high above the water does can iceberg have to be to be considered an iceberg?
6m
Can glaciers change landscapes? How so? (~3 ways)
Erosion/transport, and deposition.
What is glacial abrasion?
A “sandpaper” effect on substrate. Erodes and polishes rough grains.
What is substrate?
Fine “rock flour”; smallest grain size.
