Geology- glaciers
Terms
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- valley/alpine glaciers
- advance slowly
- ice sheets
- exist on a larger scale, flow out in all directions
- ice shelves
-
-occur when glacial ice flows into the adjacent ocean
-large, flat masses that extend seaward
-thickest on landward side - ice caps
- -cover uplands and plateaus
- outlet glaciers
- -tongues of ice that flow down valleys extending outward
- Piedmont glaciers
- -occupy broad lowlands at the bases of steep mountains and form when one or more alpine glaciers emerge fromt he confining walls of mountain tops
- firn
- -the recrystallization of snow
- flow
- -the movement of glacial ice
- two types of glacial ice
-
1. plastic flow- movement within ice
2. basal slip- when entire ice mass slips along the ground - Zone of fracture
- ice in uppermost zone, brittle
- Crevasses
- -cracks caused when the glacier moves in irregular terrain
- surges
- periods of rapid movement
- Where do glaciers move the most?
- -in areas where more snow falls in the winter then melts during the summer
- zone of accumulation
- -where snow accumulation and ice formation occur
- snowline
- -outer limits of zone accumulation
- calving
- -when large pieces of ice break off in front of the glacier-creates icebergs
- glacier budget
- -balance or lack therof between accumulation of upper end and loss at lower end
- When are glaciers stationary?
- -when ice accumulation excedes ablation and glacier front advances until the two factors balance
- When does a glacier retreat?
- -if a warming trend increases ablation and/or if a drop in snowfall decreases accumulation
- ablation
- loss at lower end of glacier
- rock flour
- -pulverized rock produced by glacial "grist mill"
- glacial striations
- -scratches and grooves in glaciers
- glacial trough
- -U shaped (wide and deep)
- hanging valleys
- -when glaciers recede, valleys of tributary glaciers are left standing above the main glacial trough
- pater noster lakes
- -when depressions on valley floor are filled with water
- cirque
- -bowl shaped depression with walls on three sides
- fiords
- -deep, steep sided inlets of the sea, present at high altitudes
- aretes
- -sharp edged ridges, come from enlargement of cirques
- roche moutonee
- -an asymmetrical knob of bedrock, formed when glacial abrasion smoothes gentle slope and plucking steepens the opposite side
- How do glaciers form?
- -from accumulating ice that gradually turns into snow
- ice plucking
- -when rock and debris get frozen onto the ice and pulled up