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glacial budget/ mass balance
the balance between the inputs and outputs
Accumulation zone
where there is a net gain of ice over the course of the year. Here the inputs exceed the outputs.
Ablation zone
where there is a net loss of ice during the year. The losses / outputs exceed the gain / inputs
equilibrium line
the boundary where gains and losses are balanced
pressure melting point
the melting point below 0 degrees caused by pressure
polythermal glaciers
glaciers that exhibit variability in their base temperature.
geomorphological process
natural processes that result in the modification of land forms on the Earth's surface
weathering
the breakdown or disintegration of rock in its original position or just below ground surface
carbonation
carbon dioxide dissolved in water forms a weak carbonic acid. This reacts with and dissolves calcium carbonate in some rocks to form calcium bicarbonate
scree
a mass of small loose stones that form or cover a slope on a mountain.
frost action
Frost weathering is a collective term for several mechanical weathering processes induced by stresses created by the freezing of water into ice.
nivation
an umbrella term used to cover a range of processes associated with patches of snow
regelation
the phenomenon of melting and freezing depending on pressure
extensional flow
when there is a sudden increase in the gradient, the ice will flow faster and, through internal deformation, the ice will become stretched and will thin.
compressional flow
a reduction in gradient will cause the glacier to slow down causing it to 'pile up' and become thicker
what are the controlling factors in ice movement
gravity
friction
mass of the ice
melt-water
temperature of ice
Permafrost
refers to the ground that remains below 0°C for at least two consecutive years. More briefly, we can define it as perennially cryotic ground.
What is a Corrie?
Known as a cirque in France and Cwm in wales .an enlarged hollow on a mountain side has a steep cliff like backwall and and a pile of scree at the base At front usually raised rock lip
What is an Arete?
When two neighbouring glaciers cut back into a mountain side and form a narrow knife edge between the two corries
what is a pyramidal peak ?
Where three or more corries erode back to back
What is a glacial trough ?
steep-sided, broadly flat-bottomed and several hundreds meters in depth. A valley formed when the glacier retreats also know as a 'u-shaped' valley
what are the factors that affect the rate of erosion of a glacier ?
mass of ice
gradient
Melt water
Rock Debris
Underlying geology
what is a ribbon lake?
deep narrow lakes found in glacial troughs
how do ribbon lakes enhance erosion?
weaker bedrock merging of a tributary glacier which can lead to greater erosion of the valley floor because of increased mass of ice narrowing of valley
what are hanging valleys?
caused by a tributary glacier. This erosion will be less than the main glacier so it is left hanging above others
what is a truncated spur?
caused by a glacier in interlocking spurs.
erosion cuts of the tips of the spurs leaving behind steep cliffs.
What is a Rouche Moutonnee?
a bare outcrop of rock that has been shaped by a glacier
how is a Rouche Moutonnee formed?
on the upstream side, an increase in pressure causes resistance of the rock outcrop to the moving ice , leads to localised pressure melting. This allows basal sliding and abrasion as the glacier slides over the rock.
What is moraine?
land forms associated with the deposition of till.
what are the types of moraine?
ground moraine
terminal moraine
recessional moraine
lateral moraine
medial moraine
what is a till plain?
a till plain is an extensive plain resulting from the melting of a large ice-sheet that has detached from the glacier
What is an Erratic?
A boulder or smaller rock that doesn't fit in with the rocks around it. Allows for direction of flow to be established.
What is a drumlin?
an oval or egg-shaped hill which is composed of glacial till and points the direction of ice flow
What is the deforming bed model?
the forward movement of ice can cause the deformation of the sedimentary bed. Stronger stiffer portions will move less than softer portions. This explains the center of the drumlins.
what is the cavity-fill meltwater model?
the result of meltwater erosion and deposition as a consequence of large flood below the ice. A drumlin shape is forced and then filled with sediment
what are fluvioglacial landscapes
landscapes associated with flowing meltwater
what are fluvioglacial processes
basal sliding
surface melting
basal melting
Glaciofluvial action
fluvial action
erosion- abrasion and cavitation
stratification
deposition
what is a meltwater channel ?
a fluvioglacial landform- channels cut out of bedrock
subglacial meltwater errodes downward
abrasion
what is an outwash plain?
a fluvioglacial landform- flat expanses of sediment in proglacial area
meltwater transports deposits but Gradually loses energy allowing for sorted deposits to be left.
what is an esker?
a fluvioglacial landform- large sinuous ridges on the valley floor
subgalcial meltwater streams may carry large amounts of sediment in confined tunnels in the base of ice. Sediment is deposited in the tunnels as the supply of meltwater decreases at the end
what is a kame delta ?
a fluvioglacial landform- small mounds on the valley floor formed under different circumstances.
englacial streams emerging at the snout of the valley floor these streams lose energy and deposit
What is a Kame Terrace ?
a fluvioglacial landform- ridges of material running along the edge of the valley floor.
supra-glacial streams at the edge of the glacier pick up and carry lateral moraine that is deposited on the valley floor as the glacier retreats.
what is a warm-based glacier
occur in temperate conditions
relatively small and range in width from hundreds of meters to a few kilometers
melting occurs in summer months
meltwater lubricates the base and sides of glacier assisting movement
all ice in glacier close to melting
temperatures at base just above PMP
what is a cold-based glacier
occur in polar regions
large vast sheets and caps of ice
temperatures remain below melting point
little erosion and transportation
any movement is by internal deformation
Carbonation
rainfall combines with dissolved carbon dioxide to form a weak carbonic acid solution
carbon from rocks reach with the acidic water to form calcium bicarbonate
basal sliding
Friction, pressure and heat form ice moving over bedrock leads to melting
meltwater acts as lubricant assisting further flow
regelation occurs when the glacier meets a rocky outcrop
increased resistance and pressure causes melting allowing easier flowing
pressure is reduced down-slope and re-freezes
Internal deformation
occurs in both warm and cold glaciers
inter-granular movements where individual ice crystals orientated themselves in the direction of glacial movement and slide past each other
involves individual ice crystals becoming deformed or broken because of stress
1-2 cm per day
rotational flow
occurs in depression/ hollows where glacial ice forms- the ice rotates/ pivots as it starts to move down-slope
Plucking
as glacier moves through valley pressure is exerted on the sides and bottom of the valley
generating friction and heat
meltwater freezes around rocks under glacier
as glacier moves it plucks the rocks
abrasion
bits of rock and stone in ice grind against bed rock
striations may arise when rocks beneath the glacier are transported along bedrock
transportation
glacier transport materials such as clay, rock and sand in the body base and surface of the glacier over long distances
the snout acts as a bulldozer pushing debris down-slope
supra-glacial- on top
englacial- inside
subglacial- beneath
deposition
summer months glacier melts and glacial till is deposited
till is unsorted, irregular debris
meltwater will also flow out the glaciers snout forming meltwater rivers
they releases outwash
outwash is sorted to become outwash plain
continuous permafrost
large, unbroken stretches of permafrost reaches depths of up to 1500 meters
discontinuous permafrost
mostly permafrost with small localised talik
sporadic permafrost
where small patches of frozen ground occur in talik
isolated permafrost
random pockets of permafrost
sub-sea permafrost
permafrost in seabed sediments
fast solifluction
when an active layer on a slope becomes heavily waterlogged due to melting
the steeper the lobe the faster and further the material will travel
up to 10cm/yr
slow solifluction
also known as frost creep
occurs when water in soil expands as freezes
forces soil particles to rise perpendicular to the ground
as ground thaws particles are dropped vertically downwards
few cm per year
ground ice
most commonly found as pore ice
developed in spaces between soil and rock particles
mostly found in most soil where temperatures are below zero at night
help to lossen material for frost creep
frost contraction and ice wedging
temperatures drop active layer freezes and contracts
cracks will form in permafrost as a result
as active layer thaws meltwater will fill cracks
cold freezes water in cracks
forming ice wedges
frost heave
occurs when soil particles or small stones are forced to the surface by ground ice
freezing occurs from surface downwards
forms ice crystals
as the ground ice expands theses crystals force soil and stones to surface
periglacial landscape
An area where soil and rock has not risen above 0 degrees for 2 consecutive years
open talik
a small area of unfrozen ground exposed to the surface
through talik
large mass of unfrozen ground beneath a small open area
closed talik
unfrozen ground completely surrounded by permafrost
sub-sea permafrost
frozen ground within seabed sediments. Originally formed on land and was subsequently submerged as sea levels rose after the last ice age
Freeze-thaw
the action of freeze-thaw results in rough, angular broken rocks
at foot of slope known as scree
characterized by block-fields or felsenmeer
between -5 and -14 degrees
Note
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