Coastal landforms and SL changes Flashcards
Backshore
Between high-water mark and limit of wave activity
Sand dunes are formed here
Change only usually takes place here during storms
Foreshore
Between high-water mark and low-water mark
Most important zone for marine processes
Visible at low tide
Offshore
Beyond point where waves cease to impact upon the seabed
Deposition of sediment mainly occurs here
Nearshore
Between the low-water mark and the point off the coast where waves no longer have any effect on the land beneath them
3 inputs of coastal systems
Coastal geology
Climate
Nature of waves
5 processes in coastal systems
Erosion
Weathering
Deposition
Wave refraction
Sea level change
2 outputs of coastal systems
Sediment
Landforms
3 types of cliffs
Horizontal beds
Seaward
Landward
Horizontal bed
Near vertical beds
Produce steep cliffs
Seaward cliff
Loose material slides down the bedding planes
Makes it unstable and dangerous
Landward cliff
Bedding planes sloping towards land
Relatively steep but stable
5 steps of how a wave-cut platform is formed
- Destructive waves break at the foot of the cliff
- Erosion, hydraulic action and corrasion in particular
- Cliff becomes undercut forming a wave-cut notch
- Cliff above is weathered and put under stress, eventually collapses
- After a series of collapses, a wave-cut platform begins to develop between the high and low water marks
3 steps of how a cave is formed
- Weakness in the rock of a headland
- Hydraulic action exploits the rock
- Cliff is undercut and a cave is formed
3 steps of how a blow-hole is formed
- Cave facing oncoming waves is exposed to full force of the waves applied to the back of the cave
- Weathering can erode the top of the cliff
- Overlying rocks can be sufficiently weakened and collapse forming a blow-hole
2 steps of how an arch is formed
- A cave is eroded on either side of a headland
- Can erode right through the headland to form an arch
2 steps of how a stack is formed
- Roof of an arch is eroded by sub-ariel processes and chemical weathering
- Roof becomes unstable and eventually collapses creating a stack
2 steps of how a stump is formed
- A stack is subject to erosion, upper part of the stack is weathered, base of the stack is eroded
- Over time the whole stack collapses creating a stump
Beach
Accumulation of sediment to create a depositional landform
Swash-aligned beach
Waves approach perpendicular to the coast
Limited longshore drift
Drift-aligned beaches
Waves approach at an angle
Sediment travels along the beach
Longshore drift
2 types of spits
Simple
Compound
Simple spit
Straight or recurved but do not have minor spits along their landward edge
Compound spit
Have a series of minor spits or recurved ridges along their landward side
4 steps of how a spit is formed
- Occurs when there’s a sudden change in coast direction (estuary/river mouth)
- Longshore drift continues to deposit sediment in line with the coast but at sea
- Changes in wind/wave refraction leads to a curved spit
- Multiple curved ends cause a compound spit
Example of a simple spit
Spurn Head, Humberside
Example of a compound spit
Hearst Castle, Hampshire