Module 8 Flashcards
Glaciers
how does ice form
snow accumulates, compacts, melts, and refreezes - changes into firn. the firn the compacts, melts and refreezes further and transforms into ice
firn
snow which has survived a summer melt season and has begun to change into ice
how do glaciers form on Mars
ice in the polar latitudes turns into water vapour when the tilt of the axis is high and wind transports it to a lower latitude. The vapour then deposits ice on the surface and the higher humidity moves surface ice stability region towards the equator. ice persists and accumulates
what makes glaciers move
gravity. they move in response to stress
movement or deformation of ice
strain
how quickly does glacier ice move
3 - 300m/year
what determines how quickly ice moves
slope of the glacier, ice thickness, temperature, valley geometry, bedrock conditions, and subglacial hydrology
how do glaciers move
basal sliding, internal deformation, and crevassing
basal sliding
requires water at the base so that it can slide over it. need “warm” ice so that a thin layer of it melts
example of basal sliding
Alaska, Rockies
internal deformation
ice deforms as a plastic material
crevassing
upper surface of ice is brittle, so fractures or crevasses form to allow movement
where are the fastest glaciers
“warm” ice where temp is close to 0. Alaska, Rockies
example of crevassing
Klutlan Glacier - Alaska/Yukon
where are the slowest glaciers
“cold” ice. Antarctica
where in a glacier does ice move the fastest
in the centre at the top
ogives
dirt bands in ice that show differential movement
why do glaciers move slower on the sides and at the bottom
friction from the surface below and beside them
glacier budgets
relationship between gain and loss of mass
positive budget
more mass gained than lost. glacier terminus will advance
negative budget
more mass lost than gained. glacier terminus will retreat
where is mass gained
accumulation area
where is mass lost
ablation (wastage) area
equilibrium line (snow line)
point on the glacier where there is neither gain or loss of mass
ice flow
flows from the accumulation area to the ablation area. NEVER FLOWS BACKWARDS
what does increased melt mean
ice front has retreated
example of ice front retreat
South Cascade Glacier, Washington
what is science showing about glacier budgets
lost more mass then they gained - negative mass balance because of climate change
moraines
landforms generated at the margins of glaciers from sediments carried down
large latero-frontal moraines
steep-sided, often ice-cored, prone to slope failure
what can latero-frontal moraines do
form significant barriers to drainage. creates impound lakes receiving glacial meltwater
what happens if the barrier/dam of a latero-frontal moraine is breached/overtopped
glacial lake outburst flood (GLOFs) released - extremely dangerous
example of latero-frontal morain impound lake
Lake Paron, Cordillera Blanca, Peru
continental ice sheet size
> 50,000 km^2
two continental ice sheets
Antarctic and Greenland
ice cap size
<50,000 km^2
where are ice caps found
often in mountainous areas
examples of ice caps
Iceland, and Southern Patagonian Ice Field
outlet glacier
radiate from the edge of an ice cap
example of outlet glacier
Iceland
valley glaciers
flow in bedrock valleys - valley with glacier ice flowing through it
example of valley glacier
Athabasca glacier
piedmont glaciers
valley glaciers that extend out onto lowlands, and open up when they flow out
example of piedmont glaciers
Malaspina glacier Alaska, Canadian Arctic
which type of glacier is a good analogue for Mars
piedmont glaciers
cirque glaciers
occupy small, semi-circular hollows in mountainous regions
examples of cirque glaciers
Rockies, Alps
ice shelf
floating part of an ice sheet or ice cap. glacier ice is connected to main mass but then extended out to sea. made of fresh water.
example of ice shelf
Ross Ice shelf, Antarctica
erosion
takes stuff from a surface
deposition
leaves stuff on the surface
where does erosion take place
at the base. clean ice does not erode - need abrasive debris
how does debris get into ice
entrained by freezing, then forms a thin basal debris zone
how does ice erode
abrasion.
abrasion
debris in ice dragged across substrate at the base of a glacier, which forms striations and smoothes rock
what kindof landforms are created by abrasion
smoothed and streamlined landforms of bedrock - not loose material
what does abrasion do to the debris carried in the ice
shapes stones (faceting), reduces grain sizes, and produces lots of silt
how else do glaciers erode
plucking
plucking
debris is released by the fracturing of bedrock from water seeping in. the water then mechanically breaks up the bedrock and fragments are plucked by the glacier
examples of landforms created by abrasion
rouche moutonee, whalebacks
example of cirques/corries
Norway, Olympic National Park
landforms of glacial erosion
chatter marks, striations, cirques, horns
corries/cirques
semi-circular erosional “hollows”
Horns
remnant peak of mountain
arete
narrow erosional ridge
glacial troughs
u shaped valleys
fjords
flooded valleys
glacial deposition
deposit debris in a range of settings: subglacial, supraglacial, proglacial, and glaciolacustrine
subglacial deposits
debris in the base of ice smeared onto substrate. forms lodgement till.
subglacial landforms
lodgement till plain that is made at the base of the ice. streamlines forms parallel to ice flow with drumlins and flutes
drumlins
half egg-shaped hills made of till (may contain sand or bedrock) formed at the base of ice. creates a basket of eggs topigraphy
example of drumlin field
Peterborough drumlin field
flutes
long narrow ridges made of till. The till was squeezed into linear cavities at the base of the ice
examples of flutes
Saskatchewan Glacier, Iceland.
ice marginal landforms
transverse to ice flow. push ridges. created by advance of the ice front in the winter
supraglacial deposits
forms lateral and medial moraines on glaciers
how does debris get onto glacial ice
rockfall debris from valley walls
supraglacial landforms
ice melts slowly from under supraglacial debris and forms kettle holes, producing irregular, hummocky, topagrophy
example of supraglacial landforms
dundas valley
what supraglacial landforms are potentially on Mars
Hummocks
Glaciolacustrine deposits
Lakes on the margins of glaciers that are fed by meltwater
kinds of sediments deposited in glacial lakes
sands and gravels deposited on deltas. silts and clays carried into a lake that slowly settle out from suspension and form laminated fine-grained deposits
what can carry sediments into lakes
icebergs carrying coarse debris which then melts out of the ice
