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Glaciers (Final)
Gary Girty GEO100-PLANET EARTH SDSU
50
Geology
Undergraduate 1
07/05/2010

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Term
Glacier
Definition
Moves under the influence of its own weight and gravity.
Term
Glaciers store...
Definition
75% of the world's freshwater supply.
Term
Glaciers cover...
Definition
10% of the land surface of the Earth.
Term
If all the global supply of land ice stored in glaciers melted, then how far would sea level rise?
Definition
Approximately 70 meters
Term
Alpine/Valley Glaciers
Definition
Glaciers that are confined to valleys
Term
Ice Sheets
Definition
Glaciers that cover more than 50,000 square km.
Term
Ice Caps
Definition
Glaciers that are not confined to valleys and cover less than 50,000 square km
Term
Two continents that contain continental glaciers
Definition
Antartica and Greenland
Term
How is a continental glacier distinguished from an alpine or valley glacier?
Definition
Size-- they exceed 5,000 square km.
Location-- They are not confined to valleys.
Term
Snowpack
Definition
Defined as the results of multiple snowfalls over a single winter.
Term
Snowflakes
Definition
Ice crystals.
Term
Powder
Definition
Composed of ice crystals and voids filled with air.
Term
Snowline
Definition
A line marking the highest point at which a glacier's winter snow cover is lost during a given season.
-Boundary between the zones of accumulation and wastage.
Term
Terminus
Definition
Marks the farthest down valley extent of a glacier.
Term
Retreat
Definition
Occurs if the amount of water and ice glacier looses is greater than the amount of snow it gains.
Term
Basal sliding
Definition
Refers to the movement of the whole glacier over bedrock.
Term
Plastic Flow
Definition
Occurs in the lower part of the glacier between the interface with the bedrock and the overlying zone of rigidity.
Term
Rigid Zone
Definition
Occurs above the zone of plastic flow.
Term
Crevasse
Definition
An open void or crack that occurs in the zone of rigidity.
Term
Glacial plucking
Definition
Produced by the movement of the glacier away from the areas where melt water has seeped into cracks and frozen.
Term
Till
Definition
Poorly sorted and un-layed debris composed of gravel, sand, and clay that was deposited by glacier.
Term
U-shaped valleys
Definition
Valleys that were once occupied by a glacier.
Term
* Cirques
Definition
Ampitheater-like depressions occuring at the heads of the glacial valleys
Term
Tarns
Definition
Glacial lakes
Term
Ice Age
Definition
Occured 1.6 or 1.8 million to 10,000 years ago during the Pleistocene Epoch.
Term
Milankovitch Hypothesis
Definition
Glacial and inter-glacial periods are likely caused by variations in the Earth's position and orientation relative to the Sun.
Term
Zone of accumulation
Definition
Upper part of glacier that is covered with snow year round.
Term
Zone of wastage
Definition
Lower part of glacier where calving, melting, and evaporation occur.
Term
Glacial striations
Definition
Grooves in polished glacial surfaces.
Term
Trunk Glacier
Definition
Main Valley Glacier
Term
Tributary glaciers
Definition
Small glaciers that feed the main valley glacier.
Term
Truncated spurs
Definition
Ridges extending down into the main glacial valley that have been truncated by the larger glacier once occupying the valley.
Term
Paternoster Lakes
Definition
Series of glacial lakes that occupy a valley once occupied by a glacier.
Term
Exotic Blocks
Definition
Blocks of granite resting on the polished glacial surface at Ohmsted Point, Yosemite National Park.
Term
Hanging Valleys
Definition
A valley once occupied by a tributary glacier. Bridalveil Creek in Yosemite National Park is an example.
Term
Rouche Mountonnee
Definition
Soothed streamlined hill cut into the bedrock.
Term
Horns
Definition
Mt. Russell and Mt. Carillon are pyramid-like in form. They were produced by the head ward erosion of glaciers that once occupied the valleys that now
surround them.
Term
Arete
Definition
Knife-sharp ridge separating adjacent glacial valleys.
Term
End Moraine
Definition
Ridge of till that lies along the terminus of the valley glacier.
Term
Recessional Moraine
Definition
Ridge of material produced by a glacier that was retreating.
Term
Terminal moraine
Definition
Ridge of material produced by a glacier that had reached its most down valley extent.
Term
Lateral Moraine
Definition
Ridge-like accumulations of till located along the margins of each valley glacier.
Term
Medial Morraine
Definition
When two valley glaciers merge, till accumulating along their interiors also merge to form a
single distinctive ridge lying between the two glaciers.
Term
Drumlin
Definition
streamlined hills of sediment.
Term
Esker
Definition
long sinuous ridge composed of water-deposited sediment
Term
Kettles/ Kettle lakes
Definition
When blocks of ice buried by sediment along the retreating margin of a continental glacier melt a depressions forms.
Term
Kames
Definition
If sediment is washed into openings and depressions at the terminus of a wasting continental
glacier, then a small hill is left behind.
Term
Eccentricity
Definition
the orbital path of the Earth around the Sun as varying from nearly circular to highly elliptical. It takes the Earth ~100,000 year to complete this cycle.
Term
Obliquity
Definition
he tilt of the Earth’s axis either toward or
away from the sun as varying over the range of 22.5o to 24.5 o. Currently, the tilt is 23.5o. It
takes the Earth about ~43,000 years to complete one cycle of this variation in tilt.
Term
Precession
Definition
the Earth’s axis wobbles like a top slowing down as it
orbits the Sun. The Earth complete one cycle of this wobble every 20,000 years.
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