❄️ glaciation sg2a Flashcards
what are the 5 geomorphic processes
weathering
mass movement
erosion
transportation
deposition
what are the 3 types of weathering
physical
chemical
biological
what are the 3 main mass movements
slumps
slides
rockfalls
what are the 2 main types of glacial erosion
abrasion: when debris in glacier scours surface, wearing it away
plucking: when meltwater gets in cracks in surface and freezes and becomes attached to glacier, pulling away pieces of rock
supraglacial debris
carried on surface
englacial debris
carried within the glacier
subglacial debris
transported at the base of the glacier
glacial till
material carried directly by the ice
- angular
- unsorted
- no orientation
- not stratified
glacial fluvial material
deposited by meltwater
- quite smooth
- sorted
- orientated same direction
- not stratified
what is a corrie
circular steep sided hollow high up on a mountain side. armchair shaped hollow
how does ftw create a corrie
- takes place on back wall creating supraglacial debris
- takes place in bergschrund crevasse
- erodes base of glacier
how does rotational movement form a corrie
glacier moves under its own weight creating rotational movement which erodes base of glacier and creates armchair shape
how does pressure create a corrie
pressure on back wall = erosion
how does ftw form a corrie in an interglacial period
- ftw continues on steep slopes = rockfalls into tarn
- can create scree slopes at base of back wall
how does pressure release weathering form a corrie in an interglacial period
- takes place on base so hollow will deepen further
how does biological weathering modify a corrie in interglacial period
vegetation may grow due to warmer temps = roofs grow into the cracks
what flows of energy form a corrie
- height and weight determines potential energy & PMP
- when PMP is reached thermal energy is created at base = meltwater = basal sliding = kinetic energy
- as glacier leaves hollow and thins, potential energy is reduced = less kinetic energy
- rocks have potential energy. when’s gravity overcomes friction = FTW
what flows of materials form a corrie
- origin: FTW=debris created which would fall down crevice
- movement: rotational slip = abrasion by the materials
- deposition: some is deposited building lip
- modification: post glaciation = FTW continues = back wall steeper
what is an arête
knife edge between 2 corries
how do arêtes form
- snow falls in hollows and create corries
- as the 2 corries share a backwall, as they erode and back steeper an arête is formed
what is a pyramidal peak
isolated point caused by erosion of 3+ corries into same mountain
how does a pyramidial peak form
same as arête but 3 backwall’s eroding into eachother
what is a glacial trough
a valley that a glacier runs through
how does a glacial trough form
- begins as v shaped valley with a stream flowing through it
- as glacial period begins, snow begins to fall into it and through diagnosis, a glacier is formed
- there may often be a tributary glacier from higher up
- FTW on the high mountains creates sub glacial debris
- this erodes sides and bottom of valley creating u shaped valley
- post glacial: tributary glacier turns into a hanging valley which often has a waterfall, often a misfit stream flowing through middle
what is a truncated spur
where a glacier has eroded through a interlocking spur
what is a hanging valley
tributary glacier hanging above main glacier (waterfall post glacial)
what is a misfit stream
river in an interglacial trough that almost seems out of place
what is a ribbon lake
forms in rock basin on floor of interglacial trough
what flows of energy create a glacial trough
- height and mass determine potential energy
- mass determines PMP
- PMP reached = thermal energy at base = meltwater = basal sliding = kinetic energy
- tributary glaciers add mass = potential energy increased
- interglacial period = warmer = more thermal energy = glacier melts
what flows of material create a glacial trough
origin: FTW = rockfall & plucked debris from valley floor
movement: basal sliding causes abrasion with deepens & steepens
deposition: rock basin may be dammed by terminal moraine
modification: FTW may create scree slopes
what is a roche moutonnee
a rounded mass of rock smoothed and striated by ice that has flowed over it
how is a roche mountonnee formed
- on stoss end: PMP is reached as ice approaches rock = ice melts = basal sliding & some abrasion
- on lee end: pressure release = ice refreezes = FTW & plucking of material which creates jagged edge
what does a roche mountonnee look like in an interglacial period
- smooth, rounded stoss end due to abrasion & some striation marks
- steep and jagged lee end due to FTW & plucking
how have flows of energy formed a roche mountonnee
stoss end: thermal energy due to pressure melting & basal sliding = thermal energy
lee end: pressure reduced = thermal energy lost so water refreezes
how have flows of material formed a roche mountonnee
origin: subglacial material FTW & plucking up stream
movement: moves due to regelation = abrasion, FTW & plucking on lee end
