Glacier Facts Flashcards
Warm-based glaciers
High altitude locations
Steep relief
Rapid rates of movement- 20-200m per year
Basal temps above pressure melting
Cold-based glaciers
High latitude locations
Low relief
Basal temps below pressure melting point
Very slow rates of movement
Factors influencing movement of glaciers
Gravity-fundamental cause of the movement of an ice mass
Gradient- the STEEPER the gradient of the ground surface the FASTER the ice will move
Internal temperature of ice - can allow MOVEMENTS of one are of the ice relative to another
Glacial budget- positive budget(net accumulation) causes glacier to ADVANCE
the thickness of the ice-influences Temp and PRESSURE MELTING POINT
Two types of zones for movements glacier
Upper Zone- ice is brittle and breaks
Lower-zone under the pressure where the ice deforms
Basal sliding
Warm based glaciers mainly move by basal sliding
If basal temp is ABOVE pressure melting a thin film of meltwater existed between Ice and the Valley floor and so FRICTION is REDUCED.
Different ways Basal Sliding can occur
Slippage
Creep/regulation
Bed Deformation
Different ways Basal Sliding can occur-Slippage
Where the ice SLIDES OVER VALLEY FLOOR as the meltwater has reduced FRICTION between BASE of the GLACIER and the VALLEY FLOOR
Different ways Basal Sliding can occur-Creep/Regulation
When ice DEFORMS under PRESSURE due to OBSTRUCTIONS on the Valley Floor-causing ice to SPREAD around and OVER THE OBSTRUCTION
Different ways Basal Sliding can occur-Bed Deformation
When Ice is carried by SATURATED BED SEDIMENTS moving beneath it on gentle gradients
Like ice being carried on ROLLER SKATES
Internal deformation-
Cold based glaciers are unable to move by BASAL SLIDING-due to basal temps being below pressure melting point
They move by INTERNAL DEFORMATION
Elements of Internal Deformation
Intergranular flow when individual Ice Crystals re-orientate and move in relation to each other
Laminar flow when there is movement of individual layers within the glacier
Extending flow
Ice moves over a STEEP SLOPE unable to DEFORM quickly enough so it FRACTURES forming CREVASSES. The leading ice pulls away a from the ice behind it
Compressing flow
When gradient reduce the ice thickens and the FOLLOWING ICE PUSHES OVER
The Slower-moving leading ICE
Weathering
Influences the formation of glacial landforms. Uses heat energy to produce PHYSICALLY CHEMICALLY altered material ps
Types of weathering-Physical
The breakdown of rock achieved by physical weathering processes that produce SMALLER FRAGMENTS of the Same Rock
