GL 2 Flashcards
What is the cryosphere?
Parts of the crust and atmosphere that are below zero degrees for a part of the year
How are icebergs formed
Broken of of glaciers into water via calving
What is permafrost
permanently frozen ground
What is the morphology of glaciers?
Form, shape and structure of ice
What two factors impact the morphology of a glacier?
Climate and topography of land
What is climate? And how does it impact a glacier’s morphology
Climate is contorlled by annual temperature cycle. Warmer climate causes negative mass balance vice versa.
What is topography? And how does it impact glaciers morphology?
Topography is the natural shape of the land. Land surface, e.g. altitude. Controls physical dimensions of the glaciers and how they can flow.
What is an unconstrained land mass?
morphology and flow pattern that is not fully dependent of the topography of land
What is a constrained ice mass?
Morphology and flow pattern that is strongly based on topography
Ice sheet:
Description, size, constrained or unconstrained?
Example
Topography is submerged in ice, forms gently sloping domes of ice several km thick. +50,000km2. Unconstrained. Antarctic ice sheet
Ice cap:
Description, size, constrained or unconstrained?
Example
Smaller version of an ice sheet. >50,000km2. Unconstrained. Vatnajökull ice sheet
Ice field:
Description, size, constrained or unconstrained?
Example
Ice covering upland area, does not bury topography. 10-10,000km2. Constrained. Patagonian ice fields
Valley glacier:
Description, size, constrained or unconstrained?
Example
Confined between valley walls, finishing in a narrow tongue, made from ice caps, sheets or cirques. 3-1500km2. Constrained, Aletsch glacier, Swiss Alps
Piedmont glacier:
Description, size, constrained or unconstrained?
Example
Valley Glacier that extends beyond end of a mountain into flat area, spreading out. 3-1000km2. Constrained. Malaspina, Alaska
Cirque glacier:
Description, size, constrained or unconstrained?
Example
Occupies a hollow on a mountain side, calves out a corrie. 0.5-0.8 km2. Constrained. Styggebrean Norway
Ice shelf/sea ice:
Description, size, constrained or unconstrained?
Example
Large area of floating glacier ice, many glaciers coalesce (fuse). 10-10,000km2. unconstrained. Larsen Ice shelf
What is thermal regime?
the temperature of the ice
What are the two types of thermal regimes, and what is the difference?
Cold based (polar glaciers) - Glacier is permanently frozen to ground. Average temperature is well bellow 0, surface temperature is -20 to -30. High latitudes.
Warm based (temperate glaciers) - Glacier is not frozen to bedrock. Temperature fluctuates to above melting point, causing meltwater, this is due to the pressure melting point (water melts due to high pressure, even while temperature is below 0 degrees celcius). High altitudes.
Why are glaciers able to move?
Glacial ice can deform
What is pressure melting?
Ice melts at temperature below 0 degrees, due to pressure of overlying ice.
What is the equation for pressure melting?
melting point falls at a rate of 1 degree Celsius for every 100kg/cm3 of pressure
In what thermal regime do glaciers melt. Why?
Warm based glaciers reach pressure melting point at depth. Causing meltwater.
Cold based glaciers do not melt as temperature is far from pressure melting point all thought the glacier.
What is Regelation
Ice melts under pressure, when pressure is relieved water refreezes
Is Basal sliding warm based or cold based?
Warm
What is Basal sliding? This is not a specific type of movement, all warm based glaciers do this.
Only occurs when there is meltwater, acting as a lubricant reducing friction, enabling movement.
What is enhanced Basal creep? Cold or warm?
Glacier comes into contact with an obstacle. Ice deforms around obstacle, but does NOT reach pressure melting point. Warm based only.
What is the Stoss and Lee side?
Stoss - up side
Lee - down side
What is Regelation slip. Cold or warm?
f temperature of ice is close to pressure melting point, increased pressure from the stoss side (up movement) of glacier will induce melting. Glacier is able to slip and meltwater flows around obstacle to the Lee side, pressure is reduced and meltwater refreezes - linking to regulation. Warm only.
What is internal deformation. This is not a specific type of movement, all warm and cold based glaciers do this.
individual grains of ice withing glacier responding to pressure, this is NOT melting. This is effected with ice thickness and slope angle.
What is intergranular flow? Warm or cold based?
Displacement of ice grains relative to one another. Bottom grains are stationary while top rotate clockwise, this is due to slope angle as it is reliant on gravity. A steeper slope angle causes more movement. Warm and cold based.
What is Laminar flow? Warm or cold based?
Layers of ice slipping over one another. Ice at the bottom has slower relative velocity then ice at top. This is due to slope angle as it is reliant of gravity. A steeper slope angle causes more movement. Warm and cold based.
What is the deformation of ice called? What is it caused by? Warm or cold?
Ice creep. Caused by increased ice thick and/or slope angle. Warm and cold
How does ice deformation cause ice faults, fractures and crevasses.
Ice is not able to deform quick enough
Explain extensional and compressing flow.
When slope gradient is increased, ice accelerated, causing crevasses. This is extensional flow.
When slope gradient is decreased, ice slows down, causing ice behind to catch up, leading to ice thickening, and crevasses to close. This is compressing flow.
What is subglacial bed deformation? Warm or cold based? What does this cause?
Glacier moves over weak, loose rock, causing sediment to deform under weight of glacier. Warm based glacier only.
In Icelandic glaciers this causes 90% of glacial movement
What thermal regime glaciers move faster?
Warm
What is the range of movement in a glacier per year?
3-300m per year
How does slope angle impact velocity?
Higher slope angle = more velocity
vice versa
How does thermal regime impact velocity?
Warm based glaciers have more velocity due to
- Water acting as lubricant
- More movement options
- Basal sliding
What are glacial surges?
Periods of rapid movements
How much faster can a glacier move in surge conditions?
Up to 1000 times faster
What are glacial surges caused by?
change of flow pattern of subglacial meltwater
Describe surge conditions
Water builds underneath glaciers. Increase of ice in accumulation zone. During winter subglacial meltwater channels are closed, increasing accumulation of ice. During summer ice accumulation is so great that subglacial meltwater channels do not open. Pressure melting point and subglacial meltwater separates basal ice from it’s bed, lubricating it and causing faster velocity. Abundant water increased pore water pressure, adding to movement, Surge occurs and glacier returns to normal flow.
What case study is used for glacial surges
Muldrow Glacier, 2021
When did Muldrow Glacier last surge? How far did it move?
1956, moving 4 miles
How far did Muldrow Glacier move? How much more is this then normal? What did this cause?
200ft in 4 days, 10-20m in one day, 100x faster then normal, caused massive crevasses
Where does Muldrow lie that impacts surge conditions
Lies on a fault line, which causes earthquakes
