Processes Of Flow Flashcards
What is stress?
Tension/ pressure acting on a body
What is strain?
Measure of deformation of a body under stress
What is shear stress?
Stress that deforms a material by sliding over another
Rheology
Plastic & Elastic response to stress
Factors that increase shear stress
Ice thickness, surface slope.
What are the 3 flow mechanisms?
Subglacial deformation.
Internal deformation
Basal sliding
What does internal deformation allow cold-based glaciers to do?
Allows them to move. Only way to make a cold-based glacier move.
What is Glenn’s Flow Law?
Large stress = rapid flow
Internal deformation increases with depth due to added friction.
Cracks form when ice moved faster than it deforms
What is basal sliding
Highly pressurised water at bed of glacier, lifts it off bed, formed by pressure and frictional heating
Pmp reached, warm-based glacier.
Fast flow.
What is Regelation?
Ice moves, reaches small lumps (rock). Increased pressure, ice melts and flows around. Stress and pressure drop. Re-freeze. This process releases latent heat. Melts ice behind it. Positive feedback.
What initiates glacial movement?
- inputs
- temperature of water & ice pmp.
- flow mechanisms
What is an ice stream?
Fast flowing channels of ice. Currently draining Antarctica.
What is an Outlet glacier?
Constrained by topography, fast moving glaciers that drain ice caps.
Negative mass balance.
Half of Greenland mass loss from outlet glaciers
What is the Zwally effect?
Warm climate = surface melt near equilibrium line.
Melt pools form & drain through cracks.
Causes basal sliding, positive feedback loop.
Warmer = faster = more in ablation zone = more meltwater etc.
What is the Jakobhavn effect?
Helheim glacier in Greenland.
Largest glacier draining ice.
Ice sheet thins, more buoyant, floating ice sheet, increased flow.
