2.a. coastal landforms develop due to a variety of interconnected climatic and geomorphic processes Flashcards
(11 cards)
what are cusps? how are they formed?
- small semicircular depressions along the shoreline. Temporary features formed by a collection of of waves reaching the same point, when swash is of equal strength to backwash
- The sides of the cusp channel incoming swash into then centre of the depression, producing a strong backwash
- Dragging material down the beach from the centre of the cusp (encouraging the depression) ripples may develop further down the beach due to the orbital movement of water in waves.
how has changing sea levels lead to spit breaching? + example
some barriers are thought to be the result of former spits being breached by high energy waves that then erode a permanent channel to form islands
Located example - Chesil Beach
- Made up of small shingle, about 4m high.
- Originally thought to be a spit which grew along the coast and became a tombolo
- Recent research suggests:
- Swash alignment may be a factor
- sediment continues to be added to the system to form cliff erosion to the west.
what are beaches?
they are dynamic
they are the accumulation of deposited material, often in a bay.
delta formation
Delta formation; large areas of sediment found at river mouths deposited by rivers and tidal currents. They form where:
- rivers have large sediment loads, Broad continental shelf, Low-energy environments , low tidal range.
- Upper delta plain - furthest from island, beyond reach of tides. Composed entirely of river deposits
- Lower delta plain - in the inter-tidal zone, regularly submerged. Composed of both river and marine deposits.
- Submerged delta plain - lies below mean water level.
types of delta
cuspate delta - pointed extension to the coastline that occurs when sediment accumulates and is then shaped by regular, gentle currents from opposite directions
Arcuate delta - sufficient sediment supply is available for the delta to grow seawards, but more wave action is strong enough to smooth and trim its leading edge.
Bird’s foot delta - distributaries build out from the coast in a branching pattern, with river sediment supply exceeding the rates of removal by waves and currents.
geomorphic processes
Geomorphic processes
Weathering - uses energy to produce physically or chemically altered materials from or near surface rock (in-situ)
Physical or mechanical :
freeze thaw - water enters cracks, freezes, expands.
Pressure release - overlying rocks removed by weathering exposing more fragile underlying rock
Thermal expansion - rocks expand when exposed to heat and contract when cooled. Constant expansion and contraction can cause flaking and cracking.
Salt crystallisation - salt solution seeps into porous rocks an crystallises therefore expands.
Chemical:
Oxidation
Carbonation
Solution
Hydrolosis
Hydration - water being added to mineral, resulting mineral has greater volume than original mineral.
describe swash and drift aligned beaches
Swash aligned beaches
usually straight and lack longshore drift movements, because waves approach perpendicularly and are fully refracted, closed systems - no net movement of sediment out of the system.
Drift aligned beaches
dominated by waves which approach at an oblique angle resulting in the movement of sand and shingle along the coastline by longshore drift, often have spits as a result.
aeolian processes
Aeolian processes:
Erosion
wind picks up and carries sand particles, Attrition on land os particularly effective in wind as particles can be carried for greater distances than in water and the particles aren’t protected against collision by the film of water.
Transportation
wind is able to transport material in the same way as water (not solution)
Only smallest grains can be carried in suspension, larger is carried by saltation or surface creep.
Deposition
material carried by wind will be deposited when the wind speed falls
Sub-aerial weathering
Physical/mechanical/chemical
Wetting and drying - the tidal cycle leads to alternation wetting and drying of rocks exposed between high and low tides
This s]cycle has significant effects on the development of coastal landscapes in the uk.
Marine erosional processes:
Marine erosional processes:
Hydraulic action (wave pounding)
force of moving water (no rock involvement) can fracture rock, wave quarrying
Pneumatic - air can be trapped and compressed between water and cliff face
Abrasion
breaking waves pick up and carry sediment such as sand, gravel and pebbles
Sediment gets hurled at the rock face
Attrition
individual sediment particles collide with each other as they are moved around by water. Reducing the size of the particles.
Bio-erosion - caused by the activity of biological organisms living in the coastal zone.
salt marshes
The formation of salt marshes: {features of a low energy environment}
vegetated areas of deposited silts and clays
Subjected to twice daily inundation and exposure (tides)
Salt tolerant plant species trap sediment, to help increase the height of the marsh overtime
Leaves and stems of the plants act as baffles and trap sediment, helping to increase the height of the marsh overtime.
Turbid - cloudy/muddy water because of sediment held in suspension.
how are wavecut platforms / notches formed? 3 types of strata?
Wave cut notch/platform formation:
destructive waves break on steeping coastlines leading to the undercutting between high and low tide marks + wave cut notch.
Soon gravity causes the rock above the notch to collapse meaning the cliff retreats inland.
At the base a sloping platform is created and dissected by abrasion, platform becomes so wide the water becomes shallow so smaller waves form.
Cliff profiles vary depending on geology e.g. strata:
- horizontally bedded
- seaward dipping
- landward dipping
- shore platforms usually slope seaward as erosion occurs between tides
- As water levels are constant between high and low tides. This is where most erosion occurs.
