coastal landforms Flashcards
discordant coastlines
discordant coastlines are made up of alternating bands of hard and soft rock at right angles to the coast
concordant coastlines
alternating bands of hard and soft rock are parallel
what can affect the rate of erosion
rock type and geological structure influence erosional landforms
hard rocks like granite take longer and soft rock like sandstone take a shorter amount of time
rocks with joints and faults like cracks erode faster
headlands and bays form along what coastline
discordant - alternating bands of less resistant and resistant rock along a coast
less is eroded faster forming a bay with a gentle slope
because the resistant rocks erodes more slowly it juts out forming a headland with steep sides
headlands are eroded forming caves, arches and stacks
- resistant rock likely has weaknesses like cracks
- waves crash into headlands and enlarge the cracks by hydraulic action and abrasion
- repeated erosion cause a cave to form
- continued erosion deepens the cave until it breaks through the headland to form the arch
- erosion wears away the rock supporting the arch until it eventually collapses
- this forms a stack
waves erode cliffs to form wave - cut platforms
waves cause most erosion at the foot of a cliff, forming a wave cut notch which is enlarged over time
repeated erosion causes the rock and notch to become unstable and it collapses
collapsed material is washed away and a new wave cut notch starts to form
after repeated collapses the cliff retreats leaving a wave - cut platform e.g. Southerndown, South Wales
beaches are formed by deposition
beaches are found on coasts between the high and low water marks
formed by contructive waves
sand beaches
created by low energy waves and are flat and wide - sand particles are small so the weak backwash can move them back down the beach creating a long gentle slope
shingle beaches
created by high energy waves and are steep and narrow - sand particles are washed away but larger shingle is left behind - the shingle particles build up to create a steep slope
spits
bars
sand dunes