marine erosion

Question 1

erosion is divided into two parts..

Answer 1

marine processes (base of cliff)
sub-arial processes (cliff face)

Question 2

marine erosion types

Answer 2

hydraulic action (storm or high energy waves hitting a sea wall or cliff foot)
cavitation (water trapped in cracks of the rock, compressed by the pounding of waves and when pressure is relased bubbles form and escape with an explosive nature)
abrasion (sediment hitting the base of the cliff from waves)
attrition (rock falls and slumps mean material is in the warer, moved by waves and hits against eachother)
solution (chemicals in the sea water dissolving rocks especailly limestone or chalk)

Question 3

sub-arial processes

Answer 3

freeze thaw wathering 
salt weathering 
expholiation
biological
carbonation
oxidation

Question 4

freeze thaw

Answer 4

water seeps into cracks on the cliff face, freezes overnight and the water exampands by 10x, this widnes and weakens thwe crack.
repeated freezing and thawinf can make the rock crumble and split

Question 5

slat weathering

Answer 5

Salt. weathering is a process of rock disintegration by salts that have accumulated at. and near the rock surface. It is the dominant weathering process in deserts. especially in coastal and playa areas where saline groundwater may be close to.
crystalisation- salt enters cracks and overtime the salt applies pressure onto the rock

Question 6

exfoliation

Answer 6

extreme tempreture variations between day anmd night= expansion and contraction of the surface layers of rock on the cliff face
the stresses caused by these changes weaken the rock and surface layers peel off, increased availability of water at the coastline can speed up this process

Question 7

biological

Answer 7

caused by roots of vegetation and nesting birds, cliffs often contrain halophytic (saly-loving) plants that grow in these cracks, widening them leading to biological weathering
seabirds sit of ledges of cliffs, their guano is extremely corrosive and can lead to the chemical weathering of some types of rocks

Question 8

sub arial processes- mass movements

Answer 8

another sub-arial process is mass movement, the movements of material downslope under the influence of gravity they can be rapid events such as rock falls or landslides or slower ones sychas soil creep

Question 9

rotational slumps

Answer 9

a common mass movement at coasts are rotational slumps,

Question 10

what does mass movement occour near a coastline?

Answer 10

weathering weakens the rockd
rainwater lubricates the cracks
water adds weight to rocks
marine processes undermine the rock making it unstable

Question 11

sources of coastal sediment

Answer 11

rivers bringing sediment from the land to the coast

erosion of cliffs

the sea- tides and waves bring material to the caostline.

Question 12

factors affecting the rate of marine erosion

Answer 12

waves
tides
currents
winds 
sediment supply 
rock reistance 
geology 
fetch length

Question 13

waves

Answer 13

wave steepness- steep destrutive waves have more erosive power thsn construtuve waves
wave breaking point- waves breaking at a cliff base= prime marine erosion, waves breaking off shore loose energy

Question 14

tides

Answer 14

spring tides= larger area zone for wave attack, neap tides= smaller zone

Question 15

currents

Answer 15

longshore and rip currents carry larger quantities of material

Question 16

winds

Answer 16

onshore winds erode fine beach sand to from dunes
offshore winds may erode dunes and nourish the beach
the longer the fetch, the greate wave-energy potential

Question 17

sediment supply

Answer 17

continual supply is necissary for abrasion and attrition, whereas oversupply can protect the coast

Question 18

rock reistance

Answer 18

e.g. granites are very resistant whereas unconsoludated volcantic ash or boulder clay have little reistance to wave attack

Question 19

rock geology/ structure

Answer 19

many joints or cracks in rocks make them suseptable to erosion
horizontal or verticle structures produe steep cliffs

Question 20

orinetation of the coast

Answer 20

headlands with verticle cliffs tend to concentrate wave energy by refraction

Question 21

topography

Answer 21

the seabed.
a steep seadbed generates higher and steeper waves than one with a gentle gradient
longhashore bars cause waves to break off shore and loose energy.