coastal landform examples CAIE A level geography coasts

Wave Cut Platfrom

Kimmeridge broad bench and kimmeridge ledges. Resistant Dolorite and limestone laminations make up the platform, cliffs are made of laminations of kimmeridge clay, dolorite, and limestone,

Factors affecting kimmeridge

1. Geology, resistant dolorite and limestone laminations allows the existence of the platform, horizontal lamination planes of the kimmeridge clay cliffs make them resistant to mass movements

2. Tectonic warping from the alpine orogeny created the purbeck monoclyne with kimmeridge formed by a anticline of the monoclyne resulting on broad bench on the eastern headland due to the pushing of the limestone upwards

Cliffs

Dancing ledge, cliffs have not changed for 100s of years

Factors affecting dancing ledge

1. Bathymetry - submerged platform offshore slows wave energy preventing erosion of the cliffs behind

2. Geology - very resistant Portland limestone platform prevents erosion of the platform and therefore the cliffs

Compound spit example

Hurst castle spit east of Christchurch bay, flint and chalk pebbles with recurve hook on the distal end

Factors affecting hurst castle spit

1. Longshore drift - sediment matches chalk cliffs at Christchurch

2. Anthropogenic - the spit is declining as longshore drift is prevented by the Hengistbury Head long groyne and groynes on Bournemouth beach

3. Sea level rise - post glacial fluvial meltwater deposits created the gravel deposits of shingles bank that top up the spit

Arch example

Durdle door, lulworth cove, bands of portland limestone and less resistant purbeck beds limestone

Factors affecting durdle door

1. Tectonic uplift - during the alpine orogeny the purbeck monoclyne formed with durdle door being an anticline with striations of differing hardness rocks creating differential erosion on the cliff and creating the arch

Example of a headland

Old Harry Rocks, old chalk seam with horizontal strata

Factors affecting old harry rocks

1. Geology - resistant chalk rock

2. Lithology - horizontal lamination planes make the cliffs resistant to mass movement

3. Sea level rise - post glacial sea level rise started erosion on the headland and resulted in the old Harry’s wife stack to turn into a stump in 1896

Bar beach and tombolo example

Chess is beach, 18km long and 14m tall tombolo, resistant to being exposed to 6.5m waves with a 4km fetch

Factors affecting chessil beach

1. Sea levels rise - evidence that an offshore bar was pushed onshore 160,000 years ago and topped up my glacial melt deposits point ice age

2. Longshore drift - Longshore grading of smaller pebbles to the east and larger to the west with the same geology to east Devon cliffs

3. Anthropogenic - building of piers along the beaches in the 1860s means the Longshore drift is not evenly distributed along the tombolo