CL - depositional landforms 1-18p Flashcards
examples of inputs in a system
- energy from:
- waves
- wind
- tides
- currents - sediment
- geology of coastline
- sea level change
examples of components of a system
erosional and depositional landforms and landscapes
examples of outputs in a system
- dissipation of wave energy
- accumulation of sediment above the tidal limit
- sediment removed beyond local sediment cells
what are sediment cells
- movement of sediment that occurs in distinct areas called cells
- a stretch along the coastline where sand is largely self-contained
- closed system
- although there are inputs and outputs of energy, the sediment stays largely within the cell
whats a sub - cell
- if part of a larger cell they are called sub cells
flamborough head-humber estuary sub cell is part of the
flmborough head the wash cell
parts of a wave and what is it
undulations on the surface of the sea driven by wind
- fetch - distance the waves travels over the sea
- height - difference between the CREST (highest part) and the TROUGH (lowest)
- length - distance between crests
- frequency - number of waves per min
how waves are formed and the process
- wave enters shallow water
- friction with the seabed increases causing the wave to slow down
- the wavelength decreases and successive waves start to bunch up
- the wave increases in height
- then plunges or breaks onto the shoreline
3 types of breaking waves
spilling - steep waves on gently sloping beaches
plunging - steep waves on steep beaches
surging - low angle waves on steep beaches
constructive waves
- low
- long length (up to 100m)
- low frequency (6-8 per min)
- the strong swash loses momentum and volume leading to a weak backwash and low sediment movement off the beach
- higher swash energy than backwash
- material is slowly and gradually moved up the beach forming BERMS
destructive waves
- high
- steep
- high frequency (10-14 per min)
- powerful backwash. where sediment is pulled away from the beach
- backwash has more energy than swash
- very little material is moved up the beach - forming STORM BEACHES
what is wave refraction
- when waves break on an irregularly shaped coastline
an example of wave refraction - headland separating two bays
- waves drag in the shallow water approaching a headland
- wave becomes high steep and short
- the part of the wave in deeper water moves forward at a faster pace causing the wave to bend
- the low energy wave spills into the bays as most of the wave energy is concentrated on the headland
tidal cycles
the periodic rise and fall of the sea surface is produced by the gravitational pull of the moon and to a lesser extent the sun
- the moon pulls water towards it creating high tide
- there is a compensating ‘bulge’ on the opposite side of the earth
- at areas between the two bulges - low tide occurs
- when the moon and sun are at right angles to each other the gravitational pull is weak - NEAP TIDE
tidal range
influences where wave action occurs and weathering processes
lithology and examples
- chemical and physical structure of rocks
- weak rock like clay erode faster than resistant rock such as basalt
concordant coastline
- bands of rock lie PARALLEL to the coastline
- the hard rock lies on the seaward side and bays develop when a weakness is eroded landward
discordant coastline
- bands of rock lie perpendicular to the coastline
- weaker rock erodes faster forming a bay and the hard rock is left forming a headland
landward and seaward dipping rocks
landward - lead to steep cliffs
seaward - cliffs follow the angle of dip
long shore drift
waves approaching te shoreline at angle creating a zig zag pattern
creates a current of water running parallel to the shoreline
rip currents
- strong currents moving away from the shoreline due to a build-up of sea water and energy along the coastline
- creates beach features such as cusps
upwelling
- global pattern of currents circulating in the oceans can cause deep water to move towards the surface which displaces the warmer water
global pattern of ocean currents
- the global pattern of ocean currents is generated by the earths rotation
- warm ocean currents transfer heat from low latitudes to high latitudes and cold ocean currents from high to low latitudes
positive sediment budget
more material added than removed - shoreline builds to the sea
negative sediment budget
more material removed than added - shoreline recedes landwards
4 physical weathering processes
- freeze thaw
- pressure release
- thermal expansion
- salt crystalisation
freeze-thaw weathering
water enters cracks and joints and expands by 10% when it freezes. this exerts pressure on the rock causing it to split or parts break off
pressure release
a type of physical weathering caused when rocks that are under a great amount of pressure no longer have to bear a heavy load, causing expansion and fracturing.
thermal expansion
rocks expand when heated and contract when cooled. when this happens lots layers may crack and flake off - insolation weathering
salt crystalisation
solutions of salt seep into pore spaces in porous rocks. then the salt precipitates - forming crystals. the growth of these crystals causes the rock to disintegrate
5 types of chemical weathering
- oxidation
- carbonation
- solution
- hydrolysis
- hydration
oxidation
minerals in rocks react with oxygen in air or water
carbonation
- rainwater combines with dissolved carbon dioxide from the atmosphere to produce a weak carbonic acid
- this reacts with calcium carbonate in rocks such as limestone to produce calcium bicarbonate - soluble
- this is reversible
solution
- any process where a mineral dissolves in water
- some salts are soluble in water
- other minerals eg iron are only soluble in very acidic solutions
hydrolysis
- chemical reaction between rock minerals and water
hydration
water molecules added to rock minerals create new minerals of a larger volume
- this causes surface flaking in rocks
2 types of biological weathering
- tree roots
- organic acids
tree roots
tree roots growing into cracks or joints in rocks and exert outward pressure.
organic acids
- organic acids are produced during decomposition of plant and animal litter
- this causes soil water to become more acidic and react with minerlas in a process called chelation
5 processes of mass movement
landslides
rockfalls
mud flows
rotational slip/ slumping
soil creep
landslides
cliffs made of softer rock slip when lubricated by rainfall
rockfalls
rocks undercut by the sea or slopes affected by mechanical weathering
mud flows
heavy rain causes fine material to move downhill
rotational slip/ slumping
where softer material overlies resistant material and excessive lubricant takes place
soil creep
very slow movement of soil particles downslope
list of erosional landforms
headlands and bays
cliffs
wave cut platforms
caves, stacks, stumps, arches
blowholes
list of depositional landforms
beaches
spits
bars
tombolos
deltas
sand dunes
