ENVS 1050 Chapter 7: Geology Notes - week 7

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Tuesday, July 1, 2014
Geology Notes - week 7
Glacial Geology
Chapter 17: all
today, glaciers cover about 10% of the earth’s surface
glaciers are part of two fundamental cycles: hydraulic and rock
transports and deposits sediment
glacier: a thick ice mass that originates on land from the accumulation, compaction and
re crystallization of snow
ice sheets: they exist on a continental scale , the low total of the poles makes them
great for snow accumulation - they flow out in all directions and are all obscure but
highest areas of terrain
ice shelves: large flat masses of floating ice that extent sea ward from the coast but
remained attached to the land along one or more of the sides, they are thickest on those
sides and become thinner as they move seaward
Valley (Alpine) Glaciers
-they are like a stream of ice that are bounded by precipitous rock walls that flow
under it’s own weight down the valley from an accumulation by it’s head.
-ice caps: completely bury the underlying landscape and they are smaller
-some outlet glaciers become ice streams that are fast flowing that drain the most of
an ice sheet
-piedmont glaciers: occupy broad lowlands at the bases of steep mountains and form
when one or more alpine glaciers energy from the confining walls of the mountain
valley
** view formation on glacial ice - page 387
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Tuesday, July 1, 2014
Movement of a glacier
-reffered to as a flow
-internal deformation: movement within the ice - solid pressure = 50m of ice
-glacial ice consists of molecules stacked on one over the other - bonds between
layers are weaker than these within each layer
-basal slip: ice mass slips across the ground - except where polar ice is frozen to the
bed rock - liquid water is present because ice decreases as pressure increases -
melting point can be below 0 degrees
-soft bedrock deformation: sediment and fractured rocks deform by friction of the
overriding glacier - water sediment and weak bedrock such as shale are easily
deformed
-zone of fracture: uppermost sone and it is brittle carried along in piggy back style by
the ice below - when the glacier moves over irregular terrain resulting cracks called
creveases and plastic flow seals them off
-surges are rapid glacial ice movements that are 100x more faster than at normal
rates
Budget of a glacier
-snow is the raw material from which glacial ice originates
-net accumulation and ice formation - zone of accumulation and the lower limit is the
equilibrium line - SNOW LINE
** the equilibrium line separates the zone of accumulation from the zone of ablation or
wastage
calving: large pieces of ice break off the front of the glacier that creates ice bergs in
places where the glacier has reached the sea or the lake
balance mass or glacial budget: balance between the upper end (accumulation) of the
glacier and the lower end of glacier for the melting point. - ice within the glacier always
moves forward
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