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Different rates of flow in glaciers
- The sides and base of
a glacier move at a
slower rate than centre
surface ice, causing
production of crevasses
- Compressing flow
- Occurs when there is a
reduction in the gradient
of valley floor, ice
decelerates and ice
mass thickens - erosion
at its maximum
- Occurs when there is a
reduction in the gradient
of valley floor, ice
decelerates and ice
mass thickens - erosion
at its maximum
- Extending flow
- Occurs where there is an increase
in the gradient of the valley, ice
accelerates and becomes thinner
leading to reduced erosion
- Occurs where there is an increase
in the gradient of the valley, ice
accelerates and becomes thinner
leading to reduced erosion
- Rotational flow
- Occurs within corries - ice moving downhill
pivots around a point producing rotational
movement
- Occurs within corries - ice moving downhill
pivots around a point producing rotational
movement
- Glacial surges
- Occur from time to time
when excessive build up of
meltwater under glacier
leads to rapid forward
movement of up to 300m in
one day, can be hazardous
to those living in glacial
valley below snout
- Occur from time to time
when excessive build up of
meltwater under glacier
leads to rapid forward
movement of up to 300m in
one day, can be hazardous
to those living in glacial
valley below snout
- Factors affecting rates of movement
- Thickness needs to exceed 60m before ice moves downslope
- Movement faster over impermeable
suface as presence of basal meltwater
facilitates movement
- Greatest velocity at firn line due
to proportional relationship
between thickness and velocity
- Centre of ice thickest - moves more rapidly than margins
- Steep glaciers flow faster than gentle ones
- Thickness needs to exceed 60m before ice moves downslope
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