Global climate 1 - Glaciers and Glaciation Flashcards
Define glacier ice:
Metamorphic rock that consists of interlocking crystals of the mineral ice, and that owes its characteristics to deformation under the weight of the over burden
- this shows that metamorphic doesn’t just mean hot, its deformation under weight
- he worded this definition this way because it applies to all metamorphic rocks
ex) quartzite is a metamorphic rock that consists of interlocking crystals of the mineral quartz……
Define Glacier
Permanent body of glacier ice, consisting largely of recrystallized snow, which shows evidence of downslope or outward movement due to gravity
Formation of glaciers; where (think altitude)
Form at or above snow line, near sea level in high altitudes, up to 6k meters in tropics
Why is ice colorless? Or is it bue?
- snow recrystallizes (melting and freezing) to ice under the weight of the overburden, and as a result of melting and freezing ice has no colour
- NOT BLUE, blue color from refraction and reflection
Describe the movement of glaciers
Downslope movement due to gravity via combination of;
- sliding at grain boundaries
- sliding at cleavage planes
- recrystallization
- basal sliding on meltwater
Velocity of glaciers; WITHIN ICE
Velocity is highest near top; few cm to m per day
Direction and velocity of terminus (toe or end of glacier)
Move up OR downslope, depending on mass balance
-few cm to m per year, 2 order of magnitude difference in comparison to ice
What are the 6 types of glaciers
6 types of glaciers:
1) Ice cap/ ice field ex. Columbian glacier (like a cap)
2) Cirque glacier (low in altitude, melts on he outer parts.. Its kind of a circle)
3) Valley glacier , carves out a valley
4) Fjord.. Kind of like a valley glacier big bigger, the glacier is melting in the sea
5) Piedmont glacier: several glaciers merging together
6) Ice sheet.. Orders of magnitudes larger (Antarctica, and Greenland)… 3km thick
How much % of ice is covered by the most abundant glacier type, and what is the glacier type? When totally melted, how high would sea levels rise?
95%, ICE SHEETS
-global sea levels would rise 66m
What are the two most important aspects about ice?
1) Density = 0.9 g/cm^3 (abnormal b/c lower density than liquid aka water, so it floats on water b/c difference in density is ~10%, thus glacier is 10% above water, 90% in water)
2) Melting SEA ICE does not raise sea level
- only continental ice does, this is b/c ice takes up more space tan water (less dense, less compact)
Ice in permafrost distribution
Distribution:
- »_space;60 degrees latitude
-max depth 1500m
Covers 20% of earth’s surface, -majority of it is below
-Melting of permafrost will do 2 things because there are 2 things in permafrost
1)ICE - will raise sea levels few more meters
2)Frozen methane in permafrost, will raise temperature when melted
Define solifluction
gradual movement of wet soil or other material down a slope, especially where frozen subsoil acts as a barrier to the filtering of water
Life cycle of a glacier, using valley glacier as an example
- Zone of accumulation in upland area. This is where snow accumulates
- at terminus, this is where it melts (opposite of accumulation), this is called ablation
- equilibrium line in the middle, where accumulation and ablation are the same
Annual mass balance
- Thru the whole calandar year, you accumulate a lot of ice from snow fall (accumulation, at back of glacier)
- now ablation, melting snow, loses some some ice
- so then the balance is the Accumulation - Ablation. The peak of the balance is at the end of the winter, when the sum of accumulation is highest, and right before ablation just starts to pick up (summer)
Are glaciers increasing or retreating? Include facts
1) About 70-85% of glaciers worldwide (regionally variable) have been retreating since ~1850. This means the mass balance is negative (more ablation than accumulation)
2) The retreat has been accelerating dramatically since ~1980
