how are glacial landforms developed? Flashcards
what is weathering?
Ubiquitous process, that uses heat energy to produce physically or chemically altered materials from surface or near surface rock.
what are the physical processes of weathering?
freeze thaw -> water enters cracks + expands 10% when freezes. Confined spaces this exerts pressure on rock = split. More freq + reg the fluctuations of temp around 0, more effective this process
Front shattering -> low temp, water trapped in rock pores freezes + expands = stress which disintegrates rock to small particles
Pressure release -> weight of overlying ice in glacier lost due to melting, underlying rock expands + fractures parallel to the surface
what are the chemical processes of weathering?
OCSHH
oxidation -> some minerals react w oxygen eg iron. Becomes soluble under extremely acidic conditions = original structure is destroyed
Carbonation -> rainwater combines w dissolved co2 to produce weak carbonic acid, reacts w calcium carbonate in rocks eg limestone
Solution -> some salts = soluble in water, dissolve in water
Hydrolysis -> chemical reaction between rock minerals + water.
Hydration -> water molecules + rock minerals = new minerals of larger volume
what happens due to chemical weathering?
decay of rock + alter chemical composition
Why are some chemical processes very important?
Those that come in to contact w weakly pacific water, due to climate change increasing levels of atmospheric co2 -> rain + ice = more acidic
What is mass movement?
When forces acting on slope material exceed forces trying to keep material on slope. Most significant processes are those acting on steep slops -> addition of material to glacier below, loading w debris + tools for abrasion
What are two types of erosion?
Plucking - meltwater seeps into joints in rocks of valley floor. Freezes + attached to glacier. As advances, pull pieces of rock away. Particularly effect at base of glacier as weight of ice mass above may produce meltwater due to pressure melting
Abrasion - as glacier moves across surface, debris embedded in its bas/slides scours surface rocks wearing them away -> sandpapering. Finer material tend to smooth + polish rock. Debris itself is worn down = rock flour
What factors influence glacial abrasion?
PDIB
presence of basal debris -> rate increases with amount of basal debris, up to a point where it produces great friction = slows down
Debris size + shape -> angular debris more effective
Ice thickness -> greater thickness, greater pressure exerted + greater rate
Basal water pressure -> presence of meltwater = sliding = abrasion
What is nivation?
Glacial process that is thought to be responsible for initial enlargement of hillside hollows
hollows form under the emerging glacier as a result of the freeze-thaw cycle and mass wasting. Over time these may enlarge and start to form corries.
what is transportation and what does the debris come from?
RAAVPA
Debris that is moved by ice
rockfall Avalanches Aeolian deposits Volcanic eruptions Plucking Abrasion
what does supraglaical, englacial and subglacial mean for the material?
Supra-glacial = surface of glacier, come from weathering + rock fall
Englacial = within the ice. May have been supraglaical material that has covered by further snowfall, fallen into crevasses or sunk into ice due to localised pressure melting
Subglacial = debris embedded in base of glacier which may have been derived from plucking + abrasion
what is deposition and what types?
Glaciers deposit load when capacity to transport material is reduced. Occurs a direct result of ablation during session periods of retreat.
Drift: materials deposited during glaciation
Till: material deposited directly by ice
Outwash: material deposited by meltwater
What are two types of till?
lodgement till -> deposited by advancing ice
Ablation till -> material deposited by melting ice from glaciers that are stagnant or in retreat
What are the three distinctive features about till?
angular in shape -> embedded in ice and not been eroded
Unsorted -> all sizes are deposited en masse, together
Unstratified -> dropped in mounds + ridges rather than layers
what are geomorphic processes?
WMAPNTD
weathering -> physical (breakdown of rocks into smaller pieces), chemicals (reactions), biological (action of plants + animals) mass movement -> rockfall + slides abrasion plucking nivation transportation deposition
