Marine Erosion Flashcards
1
Q
Hydraulic action
A
- waves crash onto a rock or cliff face —> air is forced into cracks + joints + faults within the rocks
- when the wave retreats + air expands, the high pressure causes the cracks to force apart + widen
- this causes the rocks to fracture over time
- cavitations may follow when bubbles in the water implode under high pressure + eject tiny jets of water that erode the rocks over time
2
Q
Corrasion
A
- sand + pebbles picked up by the sea from an offshore sediment sink or temporal store are hurled against the cliff at high tide, causing the cliff to be eroded
- shape, size, weight + quantity of sediment picked up + wage speed affect the erosive power
3
Q
Abrasion
A
- sediment is moved along the shoreline, causing it be worn down over time
- stones rubbing against things act like paper, wearing down material overtime
4
Q
Solution
A
- process of water dissolving rocks + material into solutions
- the mildly acidic seawater can cause alkaline rocks such as limestone to be eroded + is very similar to the process of carbonation weathering
5
Q
Attrition
A
- wave action cause rocks + pebbles to hit against each other, wearing each other down = become round + smaller
- it is an erosive process within the coastal environment but has little to no effect on erosion of the coastline itself
6
Q
Energy factors affecting the rate of erosion
A
- waves
- tides
- currents
- winds
7
Q
How do waves affect the rate of erosion?
A
- wave steepness = steep destructive waves formed locally have more erosive power than less steep constructive waves
- wave breaking point = waves breaking at a cliff base cause maximum erosion, where as waves breaking off shore lose energy
8
Q
How do tides affect the rate of erosion?
A
- neap + spring tides vary the zone of wave attack
- strong tidal currents can scour estuary channels
9
Q
How do currents affect the rate of erosion?
A
- longshore + rip currents can move large quantities of material
10
Q
How do winds affects the rate of erosion?
A
- offshore winds erode fine beach sand to form dunes
- offshore winds may erode dunes + nourish the beach
- the longer the fetch, the greater the wave energy potential
11
Q
What material factors affecting the rate of erosion?
A
- sediment supply
- beach/rock platform width
- rock resistance
- rock structure + dip
12
Q
How does sediment supply affect the rate of erosion?
A
- continual supply is necessary for abrasion, where as oversupply can protect the coast
13
Q
How does beach/rock platform width affect the rate of erosion?
A
- beaches/ rock platforms influence wave energy by absorbing waves before they attack cliffs
14
Q
How does rock resistance affect the rate of erosion?
A
- rock type influences the rate of erosion e.g. granites are very resistant, where as uncos,dilated volcanic ash isn’t
- erosion is rapid where rocks of different resistance overlie one another
15
Q
How does rock structure + dip affect the rate of erosion?
A
- well-jointed or faulted rocks are very susceptible to erosion
- horizontal or vertical structures produce steep cliffs
- rocks dipping away from sea produce gentle cliffs
16
Q
What shore geometry affect the rate of erosion?
A
- offshore topography
- orientation of coast
- direction of fetch
17
Q
How does offshore topography affect rate of erosion?
A
- a steep sea bead creates higher + steeper waves than one with a gentle slope
- longshore bars cause waves to break off shore + lose energy
18
Q
How does orientation of coast affect the rate of erosion?
A
- headlands with vertical cliffs tend to concentrate wave energy by refraction
- degree of exposure to wave influences erosion rates
19
Q
How does direction of fetch affect the rate of erosion?
A
- the longer the fetch, the greater the potential for erosion by waves
