Coastal systems Flashcards
constructive waves
low wave high long wave length low frequency high swash low backwash
destructive waves
high wave height short wave length short frequency steep wave form low swash high backwash
wave refraction
waves change direction and become parellel to shore
coastal sediment budget
the balance of sediment being added and removed from the costal system
sediment sources
where sediment is created such as the erosion of cliffs of sand dunes.
high energy coastline
Where rate of erosion > deposition
Strong prevailing winds
destructive waves
low energy coastlines
where rate of deposition > erosion
constructive waves
Biological weathering
living organisms disintegrating sediment/rocks changing its structure
physical weathering
- wetting and drying
- exfoliation
- crystallisation
- freeze-thaw
pressure exerted on rock due to change in its structure
Wetting and drying- rocks expand when wet and contract when dry
exfoliation- large sheets of rocks detatched due to pressure release
crystallisation- salt crystals deposited in cracks applies pressure to the crack
freeze-thaw- water gets into cracks and freeze causing expansion putting pressure on rock.
chemical weathering
- carbonation
- oxidation
rain and sea water contain chemicals that can react with chemical compounds in the rock altering its structure.
carbonation- rocks containing calcium carbonate (e.g limestone) react with carbonic acid (co2 and rain) forming calcium bicarbonate causing weathering.
oxidation- oxidation of fe2+ H2O + O = Fe3+ causing rock browning and weathering
Costal erosion
Hydraulic action
waves break against cliff
pushes air into gaps
compresses air
Costal erosion
Cavitation
open of cavities in the cliff due to pressure changes
Costal erosion
Abrasion
rocks thrown against cliff by waves breaking pieces of cliff
Costal erosion
Quarrying
destructive waves put heavy pressure on cliff face. Vibration of rocks dislodges rocks.
Costal erosion
Solution
chalk and limestone dissolved
Costal erosion
Attrition
smoothing and rounding of angular rocks into pebbles shingles then sand.
Erosional landform
Cave –> Arch –> Stack –> Stump
Cave- erosion causes crevices to appear in cliff face over time widens and becomes a cave. Cave grows due to wave refraction leading erosion onto the side of headland.
Arch- Caves develop of both side till they meet forming an arch.
Stack- Arch roof becomes narrower due to weathering until it collapses forming a stack
Stump- Stack is weathered by sub-arial processes until it collapses leaving a stump.
wave cut notch/platform
Destructive Waves crash into base of cliff causes erosion through Hydraulic action, Abrasion and Solution forming a wave cut notch. Process continuous until gravity causes cliff to collapse
Discordant coastline
Concordant coastline
Discordant- bands of different rock run right angle to the coast. = more coastal landforms
Concordant bands of different rock run parallel to coast.
Dorset
High energy coastline(high fetch 5km)
Old Harry Rocks- caves, stacks and stumps
Durdle Door- arch
lulworth cove- cove
st aldhelms head- headland
Sand dunes
Sand dunes are created when wind deposits sand on top of each other until a small mound starts to form
Split
Prevailing winds cause Long Shore Drift. Constructive waves moves sediment along the beach eventually depositing sediment out to sea to form a stretch of beach.
Bar
when a split forms completely across a bay
Tombolo
when a split connects an island to mainland
Mudflats
Flow of fresh water from rivers into Sheltered shorelines depositing slit/clay.
Flow of salt water into mouth with hide tides bringing in fine sediment
Flows meet causing fine particles to settle.
Builds up over time causing mudflats
Saltmarshes
Low-lying vegetation (eelgrass) grows on mudflat slowing current = uneven deposition
Pioneers colonise area.
Halophytes (plants that tolerate salt water e.g spartina) dominates area slows down sea water = more deposition.
Plant layers become thicker = salt marsh grows= land rarely gets covered by sea.
Larger vegetation grows and eventually trees.
Isostatic and eustatic change
Isostatic change is a local sea level change whereas eustatic change is a global sea level change