Glaciation Geography Processes and Landforms Flashcards
Scree
Happens on steep gradient areas due to frost shattering. Due to gravity, scree gathers at the bottom of a hill.
Nunatak
Exposed summit of a ridge that is not covered by snow
They are located within an ice field or a glacier eg Suliven In Scotish Highlands
They undergo heavy frost shattering due to proximity to the ice
Felsenmeer/blockfield
Exposed surfaces that have been quickly broken up by frost action so that much of a rock is buried inder a cover of angular sharp boulders.
Freeze Thaw weathering breaks up the top layer of the rock.
only form on slopes lower than 25°
Eg Rockies in Colorado
Solifluction
- Caused by the active layer thawing in the summer
- excessive water reduces friction between soil particles
- parts of the active layer moving down the slope
- lobate shaped masses form debris
- these are rounded, tongue-like features that form terraces
Ice wedges
The refreezing of the active layer causes the soil to contract
cracks open during the summer
meltwater enters the cracks
the cycle repeats every year deepening and widening the cracks
can be 1m wide and 2-3m deep
Frost Heave
As the active layer starts to refreeze, ice crystals begin to develop which increase the volume of the soil, causing an upward expansion in the soil surface.
Within the soil, there are stones which because they have a low specific heat capacity, heat up and cool down faster than the surrounding soil.
The soil underneath the stone is likely to freeze before the other material, pushing the stone upwards until it reaches the surface.
This can form patterned ground as the larger stones move outwards rolling down hill.
Closed system Pingos
A frozen lake with sediment on the floor insulates the ground beneath, allowing talik to exist.
Permafrost advances during the winter allowing unfrozen water to turn to ice.
Pressure increases and sediment is pushed up creating a mound.
Corrie
a bowl-shaped hollow in a mountainside that is formed by glacial erosion.
Snow accumulates in a hollow on a mountainside. The snow is compressed by the weight of the snow that falls on top of it, squeezing out air and turning the snow into ice. Over time eroding the rock.
Permafrost definiton
Permanently frozen ground where soil temperatures have been below 0° for at least 2 years.
Internal Deformation
- Ice crystals are jumbled.
- Under pressure (greatest at the base) parallel lines form as the ice crystals align.
- The ice crystals can now slide over one another due to the reduction of friction.
- this forms crevasses.
Basal Sliding(only in warm based glaciers)
Pressure between ice and an obstacle
this pressure causes ice to melt
water can flow around and refreeze
meltwater reduces subglacial friction allows for basal sliding
Rate of movement of a glacier
Gravity (gradient)
Permeability of rock (impermeable=moves faster)
meltwater (more=moves more rapidly)
ice temperature
ice mass (more precipitation to add to mass it will advance faster)
U shaped Valley
Corrie glaciers leaves source region and descends down old river valley
scouring occurs as glacier moves
a deep wide U shaped Valley is left
Ribbon Lake
glacier moves over alternate bands of hard and soft rock
sharp edged boulders carried at base erode softer rock via abrasion
a rock basin is formed
harder rock around the edges is eroded less
rock bars form acting as a dam
rainwater fills up the rock basin
a ribbon lake forms
Pyramidal Peak
-3 or more corries and aretes meet
-glaciers carve away at top of mountain
-an angular sharply pointed summit remains
Arete
-corries erode backwards through plucking and abrasion
-back walls become steeper
-a sharp knife edge ridge is left
Truncated Spurs
interlocking spurs are left behind from a river
abrasion and plucking erode tips of spurs
steep cliff like outcrops are left
Misfit stream
a stream that can’t possibly have eroded the valley in which it flows
Fjord
found in locations where the glacial erosion happened below sea level when the glacier retreats, sea water fills up the valley floor eg loch broom
Hanging Valley
-form where two glacial valleys meet
-tributary valley glacier is smaller with less mass
-valley erode less
-main valley glacier is larger with greater mass
-valley is eroded more
-tributary valley is left hanging above main valley
-waterfall flows over the edge
Erratic
Large Boulder that has been deposited when the glacier loses carrying capacity
its geology is different than the area it is found in
eg Norber Erratics, N Yorkshire
Drumlin
formed by till
the stoss end is steeper and the lee end is more shallow
they are commonly found in groups called a swarm
there are 2 theories on how they are made
Morraine
medial
lateral
terminal
recessional
push
Outwash Plain
located at the snout of the glacier
the meltwater streams deposit gravel, sand and clay throughout summer.
hydrostatic pressure is lost outside the glacier, causing material to be deposited
larger material is deposited close to the glacier as the water loses cc
eg Red glacier, Alaska
Braided Stream (always found witj outwash plain)
seasonal melt variants fluctuation in sediment load
excess sediment during low discharge disrupts the flow
rhe channel braids as it looks for a more efficent way to move
Esker eg American Canada border
formed by subglacial flow
it is a long ridge of sediment running in the direction of flow
made of sorted sand and gravel
Kame
a hill composed of stratified sand and gravel
laid down by glacial meltwater
deposited along the front of a slowly melting or stationary glacier
will collapse when the ice retreats
commonly found in cold based glaciers as there is lower hydrostatic pressure
kame terrace
sorted sand and gravel forming along the sides of a glacier
deposited by meltwater streams following along the sides of the ice
warm rock melts the ice close to it forming a long depression along which a meltwater stream can flow
Proglacial lake
cant have without terminal morraine
a lake developed immediately in front of a glacier, damned by terminal moraine
Kettle Hole
dead ice is left on outwash plain by a retreating glacier
meltwater streams bury blocks of ice under sediment deposits
the ice melts and leaves a depression in the outwash plain
Varve
lakes on the fringes of the ice are fillied with layers of deposits
a varve is a layer of silt lying on top of a layer of sand, deposited over a year.
can be used to show past climates and warmer cooler conditions as finer silts (winter) and thicker in summer
