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Chapter 17

Chapter 17- Textbook

6 Pages
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Department
Geography
Course Code
GGR100H1
Professor
Joseph Leydon

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Chapter 17- Glacial and Periglacial Processes and
Landforms 01:55
Rivers of Ice
A glacier is a large mass of ice resting on land or floating as an ice shelf in the sea adjacent to
land
They form by the continual accumulation of snow that recrystallizes under its own weight into an
ice mass
They move slowly under the pressure of their own great weight and the pull of gravity
They move slowly in streamlike patterns, merging as tributaries into large rivers of ice
Glaciers form in areas of permanent snow, both at high latitudes and at high elevations at any
latitude
A snowline is the lowest elevation where snow can survive year-round; specifically it is the
lowest line where inter snow accumulation persists throughout the summer
Apline Glaciers
Glacier in a mountain range is an alpine glacier or mountain glacier
Alpine glaciers form in several subtypes
One prominent type is valley glacier, literally a river of ice confined within a valley that
originally was formed by stream action
As valley glacier flows slowly downhill , the mountains, canyons and river valleys beneath its
mass are profoundly altered by its erosive passage
Some of the debris created by glaciers excavation is transported on the ice, visible as dark streaks
and bands being transported for deposition elsewhere
Most alpine glaciers originate in a mountain snowfield that is confined in a bowl-shaped recess
This scooped-out erosional land form at the head of a valley is a crique
A glacier that forms in a cirque is a cirque glacier, several cirque may jointly feed a valley glacier
Several valley glaciers pour out of their confining valleys and coalesce at the base of a mountain
range, a piedmont glacier is formed and spreads freely over the lowlands
A tidal glacier such as the Columbia Glacier on Prince William Sound ends in the sea, calving to
form floating ice called icebergs
Icebergs usually form wherever glaciers meet the ocean
Continental Glaciers
A continuous mass of ice is a continental glacier
In its most extensive form it is an ice sheet
Two additional types of continuous ice cover associated with mountain locations are ice caps and
ice fields
An ice cap is roughly circular and by definition covers an area of less than 50,000km^2
An ice field is not extensive enough to form the characteristic dome of an ice cap instead it
extends in a characteristic elongated pattern in a mountainous region
Continuous ice sheets or ice caps are drained by rapidly moving solid ice streams that form
around their periphery , moving to the sea or to lowlands
An outlet glaciers flows out from an ice sheet or ice cap but is constrained but a mountain valley
or pass
An ice shelf is a thick sheet of ice with a gently undulating to level surface that extends over the
sea and floats on water
www.notesolution.com
It is attached to the land along a coastal groundling line and also ma be attracted where ice flows
around islands
On the seaward side it is bounded by a steep cliff called ice front that can be 2 to 50 m or more
above sea level
Glacial Processes
A glacier is a dynamic body, moving relentlessly downslope at rates that vary within its mass,
excavating the landscape through which it flows
The mass is dense ice that is formed form snow and water through a process of compaction ,
recrystalliation and growth
A glaciers mass budget consists of net gains or losses of this glacial ice which determine whether
the glacier expands or retreats
Formation of Glacial Ice
Ice a mineral and a rock
To give birth to a glacier, snow and ice are transformed under pressure, recrystallizing into a type
of metamorphic rock
Glacial ice is a remarkable material
Formation of glacial ice is analogous to metamorphic processes: Sediments( snow and firn) are
pressured and recrsytallized into a dense metamorphic rock( glacial ice)
Glacial Mass Balance
A glacier is an open system with inputs of snow and outputs of ice melt water and water vapor
Snowfall and other moisture in the accumulation zone feeds the glaciers upper reaches
This area ends at the firn line indicating where the winter snow and ice accumulation survived
the summer melting season
Towards glacier lower end it is water (reduced) through several processes: melting on the surface,
internally and at its base, ice removal by deflation (wind); the calving of ice blocks; and
sublimation …these losses are ablation
The zone of where accumulation gain balances ablation loss is the equilibrium line
A glacier achieves positive net balance of mass – grows larger during cold periods with enough
precipitation
Glacial Erosion
The passing glacier mechanically plucks rock material and carries it way
Debris is carried on its surface and is also transported internally or englacially, embedded within
the glacier itself
Evidence that rock pieces actually freeze to the basal layers of the glacier in a glacial plucking or
a picking up process and once embedded enable the glacier to scour and sandpaper the
landscape as it moves- a process of abrasion
This abrasion and scratching produce a smooth surface on exposed rock which shines with
glacial polish when the glacier retreats
Glacial Landforms
Erosional Landforms Created by Alpine Glaciations
A. typical stream cut valleys as they exist before glaciations. Note the prominent V-shape valley
B. you see the same landscape during subsequent glaciations. Glacial Erosion and transport
actively remove much of the regolith(weathered bedrock) and the soils that covered the stream
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Description
Chapter 17- Glacial and Periglacial Processes and Landforms 01:55 Rivers of Ice A glacier is a large mass of ice resting on land or floating as an ice shelf in the sea adjacent to land They form by the continual accumulation of snow that recrystallizes under its own weight into an ice mass They move slowly under the pressure of their own great weight and the pull of gravity They move slowly in streamlike patterns, merging as tributaries into large rivers of ice Glaciers form in areas of permanent snow, both at high latitudes and at high elevations at any latitude A snowline is the lowest elevation where snow can survive year-round; specifically it is the lowest line where inter snow accumulation persists throughout the summer Apline Glaciers Glacier in a mountain range is an alpine glacier or mountain glacier Alpine glaciers form in several subtypes One prominent type is valley glacier, literally a river of ice confined within a valley that originally was formed by stream action As valley glacier flows slowly downhill , the mountains, canyons and river valleys beneath its mass are profoundly altered by its erosive passage Some of the debris created by glaciers excavation is transported on the ice, visible as dark streaks and bands being transported for deposition elsewhere Most alpine glaciers originate in a mountain snowfield that is confined in a bowl-shaped recess This scooped-out erosional land form at the head of a valley is a crique A glacier that forms in a cirque is a cirque glacier, several cirque may jointly feed a valley glacier Several valley glaciers pour out of their confining valleys and coalesce at the base of a mountain range, a piedmont glacier is formed and spreads freely over the lowlands A tidal glacier such as the Columbia Glacier on Prince William Sound ends in the sea, calving to form floating ice called icebergs Icebergs usually form wherever glaciers meet the ocean Continental Glaciers A continuous mass of ice is a continental glacier In its most extensive form it is an ice sheet Two additional types of continuous ice cover associated with mountain locations are ice caps and ice fields An ice cap is roughly circular and by definition covers an area of less than 50,000km^2 An ice field is not extensive enough to form the characteristic dome of an ice cap instead it extends in a characteristic elongated pattern in a mountainous region Continuous ice sheets or ice caps are drained by rapidly moving solid ice streams that form around their periphery , moving to the sea or to lowlands An outlet glaciers flows out from an ice sheet or ice cap but is constrained but a mountain valley or pass An ice shelf is a thick sheet of ice with a gently undulating to level surface that extends over the sea and floats on water www.notesolution.com
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