coastal processes

Question 1

what are the six main ways that waves erode the cliff

Answer 1

abrasion, hydraulic action, cavitation, wave quarrying, corrosion, attrition

Question 2

what is abrasion

Answer 2

abrasion (corrasion) is where bits of rock and sediment transported by the waves smash and grind against rocks and cliffs, breaking bits off and smoothing surfaces

Question 3

what is hydraulic action

Answer 3

air in cracks in cliffs is compressed when waves crash in. the pressure which is exerted by the compressed air breaks off rock pieces

Question 4

what is cavitation

Answer 4

as the waves recede, the compressed air expands violently, again exerting pressure on the rock and causing pieces to break off

Question 5

what is wave quarrying

Answer 5

the energy of a wave as it breaks against a cliff is enough to detach pieces of rock

Question 6

what is solution

Answer 6

solution (corrosion) is where soluble rocks get gradually disolved by seawater

Question 7

what is atrrition

Answer 7

bits of rock smashing into each other that then break into smaller bits

Question 8

what are the four main processes of transportation

Answer 8

1. solution
2. suspension
3. saltation
4. traction

Question 9

what is solution (transportation)

Answer 9

substances that are able to dissolve are carried along by the water, e.g. limestone

Question 10

what is suspension

Answer 10

where very fine material like silt and clay particles are whipped up by turbulence and carried along in the water, most kinds of eroded material is transported in this way

Question 11

what is saltation

Answer 11

where the larger particles like pebbles and gravel are too heavy to be transported through suspension so the force of the water causes them to bounce along the seabed

Question 12

what is traction

Answer 12

where very large particles like boulders are pushed along the seabed by the force of the water

Question 13

what is longshore drift (littoral drift)

Answer 13

where the swash carries the sediment up the beach parallel to the prevailing wind, the backwash then carries the sediment back down the beach at a right angle to the shoreline.

Question 14

what is deposition

Answer 14

where the material being transported is dropped on the coast

Question 15

what is marine deposition

Answer 15

where sediment being carried by the seawater is being dropped along the coast

Question 16

what is aeolian deposition

Answer 16

where sediment being carried by the air is deposited

Question 17

why does deposition occur

Answer 17

when the sediment load exceeds the ability of the water or wind to carry it, this can be either because the sediment load has increased or the wind or water flow is slowing down

Question 18

why does wind or water slow down

Answer 18

1. due to the increase in friction:
   -waves coming into shallow water or wind reaches the land, causes friction with ground surfaces which slows them down
2. due to the flow becoming turbulent:
   -if the water or wind encounters an obstacle the flow becomes rougher and overall speed decrease
3. if the wind drops then the wave height, speed and energy will decrease as well

Question 19

what are the types of sub-aerial weathering

Answer 19

mechanical, biological, chemical

Question 20

what are the types of mechanical weathering

Answer 20

freeze thaw, salt weathering, wetting and drying

Question 21

what is freeze thaw weathering

Answer 21

1. occurs when temperatures fluctuate above and below freezing
2. water enters the joints and crevices in rocks
3. if temperature drops below 0 degrees the water freezes and expands
4. over time this repeated freeze thaw action weakens the rock, causing parts to break off

Question 22

what is salt weathering

Answer 22

1. caused by saline water
2. saline water enters pores or cracks in the rocks during high tide
3. as the tide goes out then the rocks dry and water evaporates causing salt crystals to form, when they form they expand which causes pressure on the rocks, meaning that pieces break off

Question 23

what is wetting and drying

Answer 23

some rocks along the coast contain clay, when the clay becomes wet it expands which causes fragments to break off

Question 24

what is chemical weathering

Answer 24

it is the breakdown of rock through changing its chemical composition. e.g. carbon dioxide in the atmosphere dissolves into the rainwater which creates a weak carbonic acid, this acid reacts with rock that contains calcium carbonate (limestone) and the rocks gradually dissolve

Question 25

what is biological weathering

Answer 25

1. Plants put down roots through joints or cracks in the rock in order to find moisture. As the tree grows, the roots gradually prize the rock apart.
2. Many animals, like Piddock’s, drill into rocks for protection either by scraping away the grains or secreting acid to dissolve the rock.
3. bacteria like algae and lichens produce chemicals that help break down the rock on which they live, so they can get the nutrients they need.

Question 26

what is mass movement

Answer 26

the shifting of material downhill due to gravity. it is more likely to occur in coastal areas where the cliffs are undercut due to wave action, this is because it creates an unsupported overhang

Question 27

what are the types of mass movement

Answer 27

landslides, slumping, rockfalls, and mudflows

Question 28

what is a landslide

Answer 28

where the material shifts in a straight line

Question 29

what is a landslump

Answer 29

where the material shifts with a rotation

Question 30

what is a rockfall

Answer 30

where the material breaks up and falls

Question 31

what is a mudflow

Answer 31

where the material flows downslope

Question 32

what type of rocks are more likely to collapse due to little friction between particles to hold them togther

Answer 32

unconsolidated rocks, like clay

Question 33

what makes unconsolidated rock more likely to collapse

Answer 33

heavy rainfall, because it reduced friction even further

Question 34

how is runoff related to mass movement

Answer 34

because the runoff, which is the flow of water over the land is able to erode fine particles and will transport them downslope