Coastal Zone Flashcards
How do waves form at the coast?
- there is a circular orbit in the open water
- friction with the seabed distorts the circular motion to more egg shaped
- the top of the wave moves faster
- waves begin to break at the coastline
- water rushes up the beach(swash) and water from previous wave returns(backwash)
what do constructive waves do?
they build up the beach
strong swash and a weak backwash
low wave height, long wave length
what do destructive waves do?
they destroy the beach
strong backwash, weak swash
high wave height, short wave length
what are the 2 weathering processes shaping the coastline?
freeze thaw and mass movement(sliding and slumping)
explain freeze thaw?
water fills cracks in the cliff face and will freeze when the temp drops below 0. The water freezes and expands causing tension in the rock. It will melt and freeze again and again until the rock fragment grows so weak that it breaks away
explain mass movement?
it is the downhill movement of material under the influence of gravity . it occurs where there is a sudden movement in the cliff, changing the cliff face dramatically
there are 4 types of mass movement; rockfall, landslip, landslump and mudflow
what are the 4 marine processes shaping the coastline?
hydraulic action, abrasion(corrasion), attrition and solution(corrosion)
what are the factors which effect the rate of erosion?
rock type, type of wave, rock structure, shape of coast, structure of the cliff
how are headlands and bays formed? e.g. swanage bay
found where there are bands of hard and soft rock. bays form due to rapid erosion of less resistant rock and headlands are left sticking out as rocky outcrops. the bays are sheltered by these headlands and so are less eroded. headlands are more vulnerable to erosion so wave energy is contracted here
how are wave cut platforms formed?
- weakened areas of rock in the cliff face is slowly eroded away and a wave cut notch forms
- the notch gets deeper and wider through continual erosion until the overhanging cliff can’t support its own weight so it collapses
- through this continual process the cliff line retreats and in its place a sloping rocky platform is revealed at low tide - the wave cut platform
how are caves, arches, stacks and stumps formed?
- a large crack is opened up by marine processes of erosion from weak areas of rack. this crack gets deeper and wider and this leaves the cave
- the cave eventually breaks through the headland forming a small natural archway. the base of the arch is eroded etc. overhang falls etc. until it is so thin at the top it crumbles away.
- this leaves a tall tower of rock stood away from the headland - stack
- the stack is eroded overtime, leaving the stump
how is material transported along the coast?
Longshore drift (and traction, suspension, solution and saltation)
explain the process of longshore drift?
the prevailing winds create waves which pushes material up the beach in the swash at an angle. The backwash then pulls them back down the beach at 90 degrees due to gravity. The particles hit the next wave and the process happens again (zig-zag pattern) the material is transported along the coast through this process
what are 2 features of deposition?
Beaches and Spits
how is a spit formed?
sediment is transported along the coast by longshore drift. this sediment is deposited at the pint where the coastline changes direction or where a river mouth occurs. a narrow line is formed out into the sea. sometimes a secondary wind coming from another direction results in the spit having a hooked end.
