❄️ glaciation sg1 Flashcards
what is a glacier
land based ice mass which is thick enough to flow under its own weight
how much of the earths surface is covered in glaciers
10%
where are glaciers found
- high altitude (height above sea level)
- high latitude (distance from equator)
what kind of system is a glacier
open system
inputs of matter into a glacier
precipitation
avalanches
rockfall
inputs of energy into a glacier
thermal energy from sun
kinetic energy from ice moving & wind
potential energy from high altitude
processes of erosion in a glacier
abrasion
plucking
freeze thaw weathering
outputs in a glacier
meltwater
evaporation
calving ice bergs
glacial drift
sublimation
debris
thermal energy from friction
what is accumulation
gain of snow and ice to a glacier over a long period of time
what is the zone of accumulation
upper reaches of a glacier where accumulation > ablation
what is ablation
loss of ice through melting, calving, evaporation & sublimation
what is the zone of ablation
lower altitudes where ablation > accumulation
what is the equilibrium line
seperates 2 zones, accumulation = ablation
what is the glacier mass balance
difference between accumulation and ablation
- winter = positive mass balance
- summer = negative mass balance
what is dynamic equilibrium
where short term changes and inbalance, balance out over time due to negative feedback loops
what is diagnesis
1: low density fresh snowfall traps a lot of air when it survives the year as it becomes denser
2: layers of snow build onto each other so air is expelled so density increases due to pressure melting and compression
3: over a long period of time (30-40 - 100 years) glacial ice forms, becomes blue rather than white
what is a valley glacier
‘rivers’ of ice which flow down from high mountains in river valleys
- 10-30km long
- eg Swiss Alps
- could be outlet glaciers from ice sheets
what is an ice sheet
areas of thick ice spread out over land and sea
- 69% of worlds ice
- 50,000 km^2 of ice
- largest accumulation of ice
- eg Antarctica
what is pressure melting point
temperature at which ice is at the verge of melting due to pressure (does not have to be 0^c, could be lower)
what is a warm based glacier
high altitude locations
areas of steep relief
water acts as lubricant
ice moves freely and erodes rock
moved up to 1000m per year
what is a cold based glacier
high latitude locations
low relief ice frozen as base so little movement
little erosion
only moves a few meters per year
what is basal sliding
main type of movement for warm based glaciers (90% of their movement
what is slippage
when base is melted bc PMP has been reached so water acts as lubricant to reduce friction. water could also come from moulins
what is regelation
when base of ice meets a rock outcrop.
before rock: pressure increases = high temps = ice deforms & goes over rock like putty
after rock: pressure decreases = water refreezes = FTW
what is substrate deformation
when meltwater seeps into sediments under glacier so sediment becomes saturated so acts as lubricant so ice will slide (kind of like roller boots)
what is internal deformation
main type of movement in cold based glaciers due to little meltwater. slow movement
what is intergranular slip
weight of ice makes individual ice crystals change shape. ice crystals become flat so slide over each other. ice moved downslope due to gravity
what is laminar flow
the movement of individual layers within the glacier (between annual accumulation layers)
what is extending flow
ice moves over steep slope so is unable to deform quickly so ice fractures as ice in front pulls away from ice behind it
what is compressing flow
when gradient is reduced so ice thickens and flowing ice pushes over slow moving ice in front of= thicker ice = more erosion
