Alps Flashcards
What are glaciers?
Thick mass of recrystallised ice that lasts all year round.
How do glaciers form?
1) Delicate flakes accumulate.
2) Snow buried by later falls.
3) Compression expels air.
4) Burial pressure causes melting and recrystallisation (snow metamorphism).
5) Over time, firn melds into interlocking crystals of ice.
What are mountain glaciers?
Glaciers flow from high to low elevation.
- Cirque glaciers fill mountain top bowls.
- Valley glaciers flow like rivers down valleys.
- Pidemont glaciers spread out at end of valley.
- Mountain ice caps cover peaks and ridges.
What are continental glaciers?
Vast ice sheets cover large land areas, ice flows outwards from thickest part of sheet e.g. Greenland, Antarctica.
What is glacial flow?
- Thick dense ice = high pressures = creates stresses = ice deforms.
- Stresses come from weight.
- Flow from ‘high’ to ‘low’.
What are valley glaciers?
Flow in lows, can have tributaries.
What is ablation?
Transport of ice to warmer areas (lower), leading to removal of ice (ablation).
What is the ablation zone?
Snow can occur low down ablation can occur high up. There will be zones where ice accumulates and on average ice ablates.
What is zone of accumulation?
Net snow addition, snow survives summer.
What is zone of ablation?
Net ice loss.
What is equilibrium line?
Line where accumulation above = ablation below. If line is stable, glacier shape doesn’t change.
What happens if accumulation < ablation?
Toe retreats, equilibrium line rises (glacial retreat).
What is glacial sediment transport?
Act as large-scale conveyor belt.
- Pick up, transport, and deposit sediment.
- Sediment transport always downhill.
- Sediment transport is on (supraglacial), within (englacial), and under (subglacial).
What is glacial till?
Sediment dropped by glacial ice, from clay to boulders.
What happens when there’s an accumulation of till?
Moraine (beneath ice, at toe, at flanks).
What is the difference between stratified drift and unstratified drift?
Stratified drift is water sorted, unstratified drift is not sorted.
What are terminal/end moraines?
Debris carried by glacier depositied at snout.
What are lateral moraines?
1) Debris accumulates at glacial flanks.
2) Carried downwards, remains at edges.
3) At confluences, become medical moraines.
4) After retreat, leaves ridge in direction of glacial flow.
What is a ground moraine?
1) Retreating glacier dumps anything it carries in place.
2) Subglacial and supraglacial till gets left as a gently rolling cover.
What is chemical weathering and what are some examples?
Changes in atomic structure of minerals.
- Carbonation
- Acidification
- Hydrolysis
- Hydration
- Oxidation
What is carbonation?
- Atmospheric CO2 dissolves in water, makes weak acid.
- Acid reacts in some rock to give calcium biocarbonate (limestone).
- Limestone is soluble, splits into ions that are carried away.
What is acidification?
- Acids may form in groundwater.
- Anthropogenic emissions create sulphuric and nitric acids in rain.
What is hydrolysis?
- Water can chemically react with rocks (no acid). e.g. breakdown of olivine.
What is hydration?
- Water chemically reacts with some minerals without breaking bonds.
- e.g. Anhydrite –> gypsum.
