Lecture 8 - Dynamics of glaciers and ice Sheets p1

Flashcards reviewing glacier dynamics, including movements, forces, erosion, and deposition.

What is the term for the constant throughput of snow and ice in a glacier or ice sheet?

Conveyor belt

What must happen to replace the snow and ice that is lost through melting in a glacier?

Snow and ice must move from the accumulation zone to the melting zone.

What does it mean if a glacier moves at its balance velocity?

The rate of replacement of snow and ice exactly equals the rate of loss through melting at the front.

What is the name for the measure of loss and gain in a glacier?

Shalllow Balance Gradient

What is the name for the measure of rapid loss and gain in a glacier?

Steep Balance Gradient

Which glacier showcases a large amount of loss and gain?

Franz Joseph Glacier

Which glacier showcases a small amount of loss and gain?

Midrullovenbrae Glacier

What happens if more ice is delivered than is melted away (ablation)?

The glacier will advance through the landscape.

What happens if less material is being delivered than is being melted away?

The glacier will retreat back through the landscape

What are the two types of forces that act on ice masses?

Driving forces and resisting forces

What are driving forces?

Forces that are pushing the ice down the valley

What are resisting forces?

forces are the strength of the ice

What is Stress?

Stress = Force / Area

How is Shear Stress calculated?

Shear stress is calculated with these values. density of ice, the gravity, the thickness of the ice mass.

What happens when driving forces are greater than resisting forces?

The ice will move.

What is meant by 'strain' in relation to glaciers?

Strain is the rate at which a glacier changes its shape, or in other words, moves.

What are the mechanisms through which ice moves?

Ice deformation or fractures, glacier sliding, and sediment movement

How do all mechanisms of ice movement work?

All of those processes together, they all work together to create a cumulative surface movement

What is the idea of ice like a substance?

Toffee

What is tau?

Shear Stress

What is parameter a?

Ice Hardness

What are some factors affected the ice hardness?

Ice Temperature, Water Content, Ice Crystal Structure, and Debris Content

What is the importance of Parameter N?

Constant, value of 3, Strain Rate

Why do glacial cracks not reach the bed?

it's draining faster at depth.

What are the types of sliding?

Regulation, Enhanced Creep, Water Pressure

What is the concept of Regulation Sliding?

. On the upstream side of a bump, the ice is piling into this protrusion, causing higher pressure which means the melting point is going to go down.

What is the concept of Enhanced Creep?

The locally high strain rates causing the ice to become softer, it flows around the bump, and then it becomes harder again on the downstream side. So it's enhanced flow, enhanced creep.

What happens with short term fluctuations in speed of ice movements?

it's got to be dependent on the water pressure and the seasonal flux of water to the glassier bed.

What does the U denote?

Sliding Basal

What is cavitation sliding?

You're pumping water into these cavities, the water pressure is going up, it's pushing up against the ice, it's lifting the ice, it actually lifts the ice.

What did Bryn Hubbard use to collect his measurements

Potentiometers

What did Bryn Hubbard's measurements show?

How the glacier speeds up, slows down, speeds up, slows down.

What does 'n' denote?

Effective Pressure

Why does warm ice move faster?

Cold glaciers move more slowly than warm glaciers because the ice has got stronger resisting factors if it's colder

How are warm water and resisting forces related

Rapid changes in the speed of ice movement, you've got to have the presence of liquid water, so you've got to have warm based glaciers.

What happens in an accelerating glacier pulling apart

Fractures

What does it mean if a glacier is in tension?

The force greater than the ice can cope with

What happens to a glaciers movement as it moves down hill and an increase in slope angle?

Glacier moves faster

What is effective pressure

Effective pressure is the difference between the pressure pushing down, the normal stresses, and the pressure pushing up, the water pressure. It's the difference between the two

What is basal sliding?

Slididing is equal to shear stress over effective stress