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Outline. What is a surging glacier?Features of surging glaciersMechanisms of movement (two hypothesis)Surging glacier distributionHazards of surging glaciers. What Is a Surging Glacier?. Rapid flow over a short time (active stage) followed by long periods of no movement (quiescent stage)Maximu
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1. Surging Glaciers
2. Outline What is a surging glacier?
Features of surging glaciers
Mechanisms of movement (two hypothesis)
Surging glacier distribution
Hazards of surging glaciers
3. What Is a Surging Glacier? Rapid flow over a short time (active stage) followed by long periods of no movement (quiescent stage)
Maximum velocities 10x more than quiescent stage
During active stage ice is moved from upper area (reservoir) to the snout (ice-receiving)
Active and quiescent cycles usually consistent, but every surging glacier has their own cycle length
Amount of ice in accumulation zone affects surging
4% all glaciers are surging glaciers
Temporate and cold glaciers both are subject to surge
Glaciers of surge type appear to occur mostly on sedimentary rocks
4. Features of a Surging Glacier Heavy crevassing
Ice velocities increase and fluctuate
Transfer of large volumes of ice
The snout may advance (few kms in few months)
Large amounts of melt water released
Thrusting in the ice occurs at the surge front
5. Ice structures formed during quiescent phases are deformed
6. Mechanisms of MovementRigid Bed Hypothesis
Glacier lies on rigid bed of rock
Water drains at base through tunnels and drains to the snout
The tunnels eventually closes/collapse trapping water and building pressure
Basal sliding increases and friction is less
Glacier separates from its bed and cavities begin to join
Joining cavities results in water discharges easily and surge stops
7. Variegated Glacier 1982-83
8. Deformable Bed Hypothesis Ice resting on soft unconsolidated cement
Drainage through permeable sediments under the ice
Permeability is reduced and ice thickens
Pressure builds up and glacier begins to flow
Sediments return to permeable and surging ends
9. Trapridge Glacier
10. Surging Glacier Distribution St Elias mountains, Alaska range, the Wrangell mountains
11. Surging Glacier Distribution Andes, Iceland, Greenland, USSR
12. Hazards Hubbard glacier 150km long, southern Alaska
Advanced at rates of 10m/day
13. Moved across water at mouth of Russell fiord
Reached far side of mountain wall of fiord in two months, creating a lake 50kms long out of the fiord
Many of the marine mammals became trapped
Attempt to carry mammals around the ice barrier but many were left
The lake began to rise driving birds from their nests and destroyed eggs
Town of Yakutat and airport now threatened
Lake broke through the ice dam (October 8, 1986)
14. THE ENDQUESTIONS?