Glaciers - key terms 1 Flashcards
What is a névé?
- A névé is an accumulation of ice that has been compressed.
- Layers of névé compresses via diagenesis to form glacial ice.
What is firn?
- Ice that has been present for more than a year.
- Accumulation of ice on top leads to diagenesis.
What is diagenesis?
- Diagenesis is the process of more ice accumulating, increasing the mass.
- Compression removes air, forming glacial ice.
What is a system?
A system is the relationships between objects, with inputs and outputs.
- closed or open
What is the difference between an open and closed system?
- Both have inputs and outputs.
- Open has movement of material and matter, therefore has processes like erosion, freeze thaw, GPE, KE.
- Closed systems have inputs and outputs of energy but no movement of material.
What type of system is a glacier?
An open system.
what is a glacial mass balance (aka budget)?
The difference between the amount of snow and ice accumulation and amount of ablation in a 1 year period in a glacier.
- Ablation - Accumulation = GMB
Annual glacial budget formula
Ablation - accumulation
what is a positive glacial budget?
- More ablation than accumulation
- Ice is lost so glacier retreats
- Equilibrium shifts up valley.
what is a negative glacial budget?
- More accumulation than ablation
- Ice gained so glacier advances
-Equilibrium moves down the valley.
What is ablation and how does it happen?
- Loss of ice
- Due to evaporation, melting or sublimation.
What is accumulation?
- The addition of ice to a system.
What does it mean when a system is in dynamic equilibrium?
- When equilibrium is disturbed
- Equilibrium is restored by feedback
- Negative or Positive feedback
What is positive feedback?
System shifts further from equilibrium
What is a pressure melting point?
The temperature ice melts at when under pressure.
What is creep?
The slow downward movement of loose rocks or soil down a slope.
What is slippage?
The circular motion that can cause ice to move away from the back wall.
What is basal sliding?
- When the movement of a glacier is lubricated by meltwater because the pressure meltwater has been reached.
- In warm based glaciers
What is internal deformation?
- In cold based glacier
- Ice frozen to bedrock
- The movement of a cold based glacier is slow.
- Ice layers must move and change shape leading to ice movement.
What is laminar flow?
- A type of internal deformation
- When ice layers move within a glacier
What is inter-granular flow?
- Type of internal deformation
- Ice crystals re-orientate individually and move.
What is extending flow?
- Type of internal deformation
When crevases are formed because leading ice breaks off from behind.
What is compressing flow?
- Ice moves over obstacles on a low gradient land
- Accumulation of thicker ice because the glacier does not have enough energy, or is frozen to bedrock (cold based) so can’t move past.
What are the 2 types of basal sliding?
- creep
- slippage
What is a Valley glacier?
- Confined sides
- usually move down a pre-existing valley
eg. snowdonia
What is an ice sheet glacier?
- Largest accumulation of over 50,000km2 of ice.
- Only 2 on the planet: Greenland and Antarctica.
What are the 4 types of internal deformation?
- Extending flow (breaking away)
- Compressing flow (over object = accumulate)
- Inter-granular flow (individual ice crystals)
- laminar flow (layers of ice move)
What is the difference between a cold and warm based glacier?
- Cold based:
= high latitude. less dynamic. Basal temps below pressure melting point. Internal deformation. Little seasonal variation. - Warm based:
= High altitude. Steep relief. basal temps above pressure melting point so basal sliding. Move 20-200m per year. High seasonal variation.
