Cryosphere Flashcards
Cryosphere
part of earth’s surface that remains frozen
The cryosphere takes up approximately ___ of the surface of the earth
1/3
Sea ice comprises ___ of the cryosphere
2/3
Glaciers comprise ___ of the cryosphere
10%
The frozen ground comprises ___of the cryosphere
20%
How does snow reduce surface temperatures
Snow is a highly reflective surface (high albedo) so that sunlight bounces back into space, reducing surface temperatures.
When the formation of snowfall _____ seasonal melting, this contributes to the formation of glaciers and ice caps.
exceeds
Snowline
marks a boundary of an area that has snow year-round.
Snowline location is controlled by:
variations in the thickness of winter snowpack and local topography, which its altitude typically changing from year to year depending on winter snow accumulation and summer melting.
Primary ways in which snowline elevation varies
- it is at a lower elevation in polar areas where temperatures are colder
- it is lower in coastal areas where there is more moisture and therefore snow
The process to form firn
- existing snow is compacted by newer snow
- evaporation occurs at the points of snowflakes
- moisture freezes between the points
Firn
a granular snow
Firn gradually loses interstitial air to become ___.
ice
As depth and time increase, the grains of ice become _______.
larger (due to recrystallization)
Glaciers
Above a snowline, snow accumulates to form ice. Ice masses that flow under the influence of gravity are called glaciers.
Glacial flow is fastest at the ____ of the glacial channel.
center
Glacial flow is slowest at the ____ of the glacial channel due to ____.
edges of the channel due to friction with the bed
In warm glaciers, movement occurs in:
due to internal flow and sliding at the base
Cold glaciers do not slide because:
cold glaciers are frozen into the underlying bedrock and cannot slide
Glaciers flow as ice crystals deform under stress. The deformation of ice crystals causes the ____ of ice crystal structures.
alignment
Warm (temperate) glaciers
Have meltwater at their base, which allows for a flow along the bedrock. This causes warm glaciers to have a rounded terminus (or toe).
Cold glaciers
Do not flow at their base. This causes cold glaciers to have a cliff terminus, including a cliff shape and avalanches at the bottom as the top moves the fastest.
Region of accumulation
A region in a glacier where mass is net added
Region of ablation
A region in a glacier where mass is net lost.
Ablation is caused by:
melting, evaporation, or calving (breaking off part of the ice from the glacier)
Calving
breaking off part of the ice from the glacier
Accumulation and ablation areas of a glacier are separated by an _____.
equilibrium line
Receding glacier
A glacier with a negative mass balance
Glacier mass balance
accumulation minus it’s ablation
How glaciers erode bedrock at their base:
Freeze-thaw cycles, and physical abrasion and plucking of rock fragments from the bedrock
Chatter marks
crescent-shaped gouges that can form as rock fragments are dragged across a bedrock by a glacier
Striations
linear gouges or scratches left in bedrock by glaciers as they move sand and rock fragments at their base.
U-shaped Valleys
Valleys with steep sides and broad, flat bottoms are a typical erosional landform left by glaciers.
Hanging valleys
often present at higher elevations and feed into U-shaped valleys
Three types of erosional features
Cirques, Aretes, and Horns
Cirques
bowl-shaped valleys formed at a glaciers head (by one glacier)
Aretes
sharp-edged ridges formed by two glaciers
Horns
pointed pyramids (formed by 3 glaciers)
