landforms of erosion Flashcards
how are headlands and bays formed
discordant coastlines have alternating bands of hard and soft rock
erosion dominates soft rock forming bay
resistant protruding out as headland
wave refraction then focuses energy on headland
dissipation of waves energy on bay leads to build beach up
example headland/bay
swanage bay (bay)
ballard point
durlston head
(headlands either side)
wave cut platform definition
gently sloping marine platform at base of cliff
found areas of resistant geology
cliffs and wave cut platform formation
1) marine erosion erodes foot of cliff at high tide concentrating high energy on small area
2) cliff gets undercut - wave cut notch forms
3) over time notch gets bigger and overlying rock becomes unstable and collapse
4) cliff retreats and material washed away by sea
5) after several cliff falls wave cut platform is formed
max 0.5km inland
- have further to travel in shallow water
so wave break earlier and dissipate their energy limiting growth of the platform
wave cut platform example
Kimmeridge Bay - wavecut platform
Dorset
geo cave blowhole arch stack stump
joints in cliff eroded by cavitation and wave quarrying
joint widened form narrow inlet - GEO
joints that are further eroded form CAVE
where erosion is vertical BLOWHOLE can form
otherwise continued erosion such as abrasion from eroded cliff material deepens the cave and meets another cave on the other side of the headland
ARCH
continued marine erosion and subaerial weathering widens the arch making it unstable and they keystone is unsupported
arch collapses leaving isolated portion of rock called STACK
sea will erode the stack causing a wave cut notch and eventually lead to collapse to form STUMP
example arch stack stump
Dorset, Jurassic Coast:
Old Harry rocks - stack stump
Durdle Door - arch
what determines cliff angle
dip of the rock strata.
1) Horizontal or landward dip produces steep cliffs
2) Seaward dip produces shallower slope angle - also be produced when material unconsolidated
