Cold Environments Flashcards
What is albedo?
Where snow and ice reflect most incoming solar radiation, creating a permanent deep freeze
How does frost weathering work?
Water, trapped in confined rock joints or crevasses, expands by 9% of its volume on freezing, which shatters the rocks
What several factors control the effectiveness of freeze-thaw weathering
The number of freeze thaw cycles
The availability of moisture
The density of jointing I’m rocks
What are glaciers?
Are large bodies of ice formed from compressed snow
Why do glaciers move?
They move downslope due to their own weight and gravity
What are the three main types of glaciers?
Ice sheets
Ice fields (ice caps)
Valley glaciers
Why do ice sheets submerge the landscape?
Because they often are 2-3km thick
What is the largest type of glacier?
Ice sheets
What are island peaks surrounded by seas of ice due to being covered by glaciers called?
Nunataks
What are ice fields?
Miniature ice sheets covering areas less than 50000 km
What are valley glaciers?
Giant tongues of ice that flow down from the snow line in mountainous regions
What are small mountain glaciers called?
Cirque glaciers
Where are small mountain glaciers often confined to?
Bowl-shaped depressions at the head of glacial valleys
What are valley glaciers that flow from ice fields called?
Outlet glaciers
What are valley glaciers which leave the mountains and spill into lowland regions before merging called?
Piedmont glaciers
What are the three steps in the forming of glacier ice?
Snow
Firm
Glacier Ice
What is ablation?
Melting and sublimation
What converts snow into firn?
Freeze thaw and the weight of overlying snow
What differs firn from glacier ice?
Firn still has some air left
How long does the formation of glacier ice take?
40-50 years
What controls the long term behaviour of glaciers?
Changes in mass balance or annual budget
What does a positive balance do to a glacier?
Increases total mass of ice, causing glaciers to advance
What does a negative balance do to a glacier
Reduces the ice mass and results in glacier retreat
Where does snow accumulate on a glacier?
The zone of accumulation
Where does snow melt
The zone of ablation
What did research in the Cascade Range in the U.S. Pacific Northwest find?
There were 16 years between 1984 and 2006 when glaciers had a cumulative negative mass balance
What does glacier flow rate depend on?
Valley gradient and the base temperature
What are the two types of glacier movement?
Internal deformation and basal sliding
What is internal deformation?
Ice crystals in glacier rearrange into parallel layers and slide past each other
What is internal deformation caused by?
Weight of the ice and gravity
What is basal sliding?
Where meltwater lubricates the base of the glacier, reducing friction and allowing the ice to move freely
When does basal sliding occur?
Either when: intense pressure causes melting and/or meltwater seeping down from the surface through cracks in the ice
Where does ice melt?
High pressure regions
Where does ice freeze?
Low pressure regions
What two locations do cold environments form?
High latitudes and mountains
How do crevasses form?
When fracturing and faulting of ice occurs at the surface layers of a glacier
What is a moraine?
Deposits of rock left by glaciers
What are the three types of moraines?
Terminal
Lateral
Medial
What are terminal moraines?
Moraines found at the terminus or the furthest (end) point reached by a glacier
What are lateral moraines?
Moraines found deposited along the sides of the glacier
What are medial moraines?
Moraines found at the junction between two glaciers
What are surface moraines found on the surface referred to as?
Supraglacial
What are moraines transported in ice called?
Englacial
What are moraines transported below the glacier called?
Subglacial
What often determines whether glaciers are Supraglaical or Englacial?
If the moraine is above the equilibrium line (englacial) or below (supraglacial)
What are cirques?
Deep bowl-shaped depressions, enclosed on three sides by steep rock walls.
What are cirques also called?
Corries
Where are cirques found?
Mountain heads
What are cirques the source of?
Valley glaciers
On what slope side do Cirques develop?
North-east
What is evidence that cirques develop on the North-east slopes?
71% of cirques develop on the north-east slopes of the Northern highlands in Scotland
What are cirques a type of?
A feature of erosional landform
What is the main cause of erosion in Cirques?
Rotational flow
How does rotational flow work?
Cirques, under the force of gravity and lubricated by basal meltwater, slide downslope.
Why does rotational flow contribute to glacial erosion?
It helps abrades the bedrock by plucking the bedrock at the top and using that rock to abrade the bedrock as it moves downslope
Where do the rocks used for abrasion enter the glacier?
The bergschrund crevasse
Define glacial erosion
Simply the carving and shaping of the land beneath a moving glacier
Define plucking or quarrying
The erosion and transport of large chunks of rocks
How does plucking work?
As a glacier moves over the landscape, water melts below the glacier and seeps into cracks within the underlying bedrock. This water freezes and melts, weakening the bonds holding pieces of bedrock in place. These pieces of rock can now be picked up or plucked from their rocky base and carried along with the moving glacier.
Define abrasion
The erosion that occurs when particles scrape against each other.
How does abrasion work?
The enormous weight of the glacier, along with rocks and sediment plucked up and clinging to its belly scratch and carve the rock surface below
What is a small mountain lake of trapped water called?
A tarn
What happens if a mountain is eroded by multiple glaciers?
It leaves a glacial horn
What happens if two glaciers slide down opposite sides of a mountain?
An arete is formed
What is an arete?
A sharp, narrow mountain ridge
What is a roche mountonnee?
A mass of rock shaped by a moving glacier, with one side abraded and smooth while another is jagged and rough due to plucking
