coastal processes Flashcards
hydraulic action
force of water exerting pressure on rock surface weakening it
wave quarrying
wave with trapped air hits cliff and air forced into cracks
when wave recedes explosive effect of air released
abrasion
material hurled at cliff
attrition
rocks hit each other and become smaller and rounder
solution
dissolving of calcium based rocks such as limestone
factors affecting erosion
- steep waves=more erosive
- wave breaks close to cliff= more energy released
-further travelled = more energy
-steep shelving = steep waves
-wider flat beach dissipates high energy better
-shingle beach reduces by friction and percolation
-sea defences may decrease here but increase erosion elsewhere
what is lithology
characteristic of the rock
resistant = chalk / granite
soft = clay
jointed = limestone
what is concordant coastline
when bands of rock lie parallel to coast
hard rock bands protect from erosion
what is discordant coastline
bands of rock like perpendicular to coast meaning bays and headlands form as weak bands are eroded faster than hard
how does strata impact erosion
horizontal and inland dip = steep cliff
dip seawards = sloped (varying steepness depending on dip degree)
traction
large stones rolled along seabed
saltation
small stones bounce along seabed
they can dislodge other stones
suspension
fine material such as silt is carried by water
murky water
solution
dissolved material transported in water
what is LSD
- swash moves up sediment up beach at angle according to prevailing wind direction
- backwash moves perpendicular to beach due to gravity
- this continues and sediment is moved along the beach
what is marine deposition
- material dropped due to lowered energy
- happens where waves are low energy or abundance of mateial
what is aeolian processes
transport sediment by wind
air moves depending on pressure differentials
large tidal range exposes lots of snad
travels close to ground and short distance
forms sand dunes
surface creep and saltation
surface creep (aeolian)
wind rolls or slides sand along surface
saltation (aeolian)
wind strong enough to lift grains in airflow for up to 20m
what is subaerial weathering
processes that breakdown the coastline.
mechanical/chemical/biological
mechanical weathering
FREEZE THAW
- water enters cracks and freezes
- water expands by up to 10% so it exerts pressure on rock widening crack
- melts and rock breaks off
biological weathering
PLANT ROOTS
- grow roots into rocks causing rock to flake away
ANIMALS NEST
- birds etc burrow into cliff face
chemical weathering (6 types)
SOLUTION
-salt from seawater corrodes rock
-acidic rainwater dissolves carbonate rocks
OXIDATION
- oxygen in water reacts with minerals in rock causing it to disintegrate
HYDRATION
- water and minerals in rock addition reaction causing rock to expand weakens cracks allowing further weathering
HYDROLYSIS
- acidic water reacts with minerals in rock producing dissolvable salts which dissolves rock
CARBONATION
-co2 in rain makes weak carbonic acid. this reacts with calcium carbonate in rocks forming calcium bicarbonate which then dissolves in water
-effective in cold places
ACID RAIN
-acid rain reacts with minerals in rock dissolving it
-due to industry gases in atm
mass movement
downhill movement of sediment
can be rapid or gradual
landslide
downslope movement of blocks of rock down a flat slide plane, maintaining contact with the cliff surface throughout
in consolidated rocks with joints or bedding planes sloping seawards.
rockfall
individual rock fragments break away and fall to base of cliff
very rapid
scree at bottom
mudflow
saturated soil flows downhill due to gravity triggered by heavy prolonged rainfall
lobe of material at bottom
rotational slip
upper layer saturated and water cant percolate to clay
upper layer heavy
cliff slides down curved slide plane in rotational movement
wave removes slumped material and cliff retreats
scarp at top and foot + toe at bottom
fast, common for sands and clays
soil creep
very slow movement of individual soil particles downslope
creates terracettes
