Glacier Movement

Question 1

What is a Cold-Based glacier

Answer 1

Occur in high latitudes, ice temp being below 0 as a result of surface temp of -20 to -30. Ice may be up to 500m thick. Little surface melt, little meltwater, and glacier permanently frozen to bed.

Question 2

What is a Warm-Based glacier

Answer 2

Temp of surface layer fluctuates above or below 0, but the most of the ice is close to 0. PMP means basal meltwater. Significant subglacial deposition features.

Question 3

What is Basal Sliding

Answer 3

Can account for up to 75% of movement in warm glaciers, 0% in cold based
- Enhanced basal creep: Ice deforms around obstacle, PMP not reached
- Regelation slip: Ice temporarily melts into a plastic as it goes around an obstruction due to PMP, then refreezes.

Question 4

What is Internal Deformation

Answer 4

Intergranular flow: Individual ice crystals deform under pressure and move in relation to each other
Laminar flow: Movement of individual layers within the glacier.

Question 5

What is Extensional and Compressional Flow

Answer 5

Extensional: When slope gradient increases so does the ice. Ice thins, surface cracks and bergschrund + crevasses form.
Compressional: When slope gradient decreases again, ice decelerates and closes up crevasses.

Question 6

What is Subglacial Bed Deformation

Answer 6

Glacier moves over loose sediment or unconsolidated debris, which shifts and takes the ice with it.

Question 7

What are the 5 factors that impact the rate of movement?

Answer 7

Altitude, slope, lithology, mass, mass balance.

Question 8

What is the process leading to a glacial surge?

Answer 8

Water builds up underneath glacier as standard.
During winter, meltwater channels close.
During summer, as a result of increased ice thickness, they stay closed.
PMP and subglacial water separate basal ice from its bed, lubricating it and causes overlying ice to flow.
Abundant water increases pore water pressure.