3.1.3.2 Coastal processes Flashcards
what is strata
layers of rock
Factors affection erosion:waves
Size and type of waves
most erosion is in winter months due to storms where the destructive waves are most powerful: which inc rate and amount of erosion
Waves also loose there energy further from the coastline which means they erode less, Shingle teachers are steeper so waves break later
fetch also influence amount of erosion
due to coastline configuration sheltered bays erode leads due to wave refraction
what is bedding planes?
natural breaks in the strata due to change in sediment type or depositional conditions.
what is a joint
In geology, a joint is a natural fracture or break in a rock layer where there’s been no or very little movement of the rock on either side of the fracture
lithology vs geology
characteristics of a rock vs type of rock
rock notes?
lithology (its strength and chemistry) is important in determining the rate of erosion.
Granite (resistant) will erode more slowly compared to clays or shales.
Holderness coast (till & clays) has seen a recession of 120m in the last century, whereas Lands End (granite) has eroded only 10m!
The presence of beaches will reduce erosion as wider beaches absorb more wave energy
define LSD
longshore drift is the zigzag movement of sediment along a shore caused by waves going up the beach at an angle (swash), and returning at right angles (backwash). This results in the gradual movement of beach material along the coast
how many sediment cells in England and wales
11
6 types of erosion
cavitation
solution
hydraulic action
attrition
abrasion
wave quarrying
what is hydraulic action
Force of the water, waves can generate energy of 25-30 tonnes per m-2
When wave breaks and hits coastline it momentarily traps air in cracks or joints in the rock creating high pressure which is forced against the rock.
When wave retreats the air can be seen & heard to explode back out.
When repeatedly occurring over long periods of time the rock can crumble.
This is sometimes referred to as wave pounding
what is wave pounding
when wave retreats and air explodes repeatedly causing the rock to crumble
what’s cavitation
same process with the exception off:
As a wave recedes, the compressed air expands violently, exerting pressure on the rock and causing bits to break off
what’s wave quarrying?
Action of waves breaking against unconsolidated material that ‘scoops’ it and removes rock by breaking it off.
Unconsolidated rock is rock that has spaces between the grains so easily eroded like sandstone or clay.
corrosion and abrasion
Rocks within the wave are thrown against the cliff/rock and grind or rub against during contact.
Corrasion is the force of the rock hitting the cliff whereas abrasion is the rubbing (sandpaper) effect that occurs during this action.
This further weakens and breaks bits of rock off.
This can also result in the smoothing of the rock.
This is apparent on inter-tidal rock platforms where sediment is drawn back and forth, smoothing the platform
solution/corrosion
The process of chemical reaction between sea water and rocks.
Sea water can dissolve alkaline rock (chalk or limestone)
Difficult to distinguish from carbonation (carbon cycle) which is a good example of erosion and weathering working collaboratively
attrition
The action of particles within the sea/wave hitting or rubbing against each other.
This reduces the size and angularity of sediment particles.
4 types of cliffs?
horizontal layer: HA CAVITATION
Inland dip: weathering
steepy seawards: weathering
rock dips gently seawards: weathering
rock cycle
1) magma cools and condenses into igneous rocks which is hard and resistant
2)this gets broken down by erosion
3) this causes small parts which compress and layer
4) these parts and venerable to erosion as it has faults and points of weakness
5) it compresses into sedimentary rock
6)as it comprises more the weight increases until bottom layer hits mantle
7) Due to intensive heat it melts into metamorphic rock.
