Coasts-Lesson 5-6 Coastal Processes

Question 1

What are the 6 marine erosion processes?

Answer 1

Wave pounding
Wave quarrying 
Hydronic action 
Abrasion/corrasion 
Attrition 
Solution/corrosion

Question 2

What is wave pounding?

Answer 2

• Mass of water in a wave is very powerful

- steep waves have a lot of energy and when they break against the cliff foot or sea wall they release shock waves

Question 3

What is wave quarrying?

Answer 3

• the action of waves breaking against unconsolidated material such as sand and gravels
• waves scoop out the loose material

Question 4

What is hydronic action?

Answer 4

• the weight of water being forced into a joint traps air
• force of water compresses the air causing pressure to build on the surrounding rock
• process continues leading to eventual weakening and breaking off of rock pieces
• storms may remove large chunks of the cliff which leads to extensive damage to sea defence
• the changing pressure leads to cavitation

Question 5

What is cavitation?

Answer 5

• the violent effervescence of air bubbles coming out of solution as the pressure drops
• the resultant shockwaves can enlarge rock fractures and fragment the cliff

Question 6

What is abrasion/corrasion?

Answer 6

• pebbles stones and smaller sized particulate are moved by waves and then hurled against the cliffs by waves
• the greater the wave the larger the load meaning the wave causes more damage

Question 7

What is attrition?

Answer 7

-the breaking down of already eroded rocks as well as smoothing and rounding them

Question 8

What is solution/ corrosion?

Answer 8

-chemical reaction of seawater or spray which can corrode several rock types

Question 9

What are the 5 processes of transportation?

Answer 9

• traction
• saltation
• solution
• suspension
• longshore drift

Question 10

What is traction?

Answer 10

-traction is when rocks and pebbles are rolled along the seabed by the seawater

Question 11

What is saltation?

Answer 11

-saltation transports small stones and material in a leapfrogging motion across the seabed

Question 12

What is solution? Transportation

Answer 12

-solution is when dissolved material is moved with a mass of water

Question 13

What is suspension?

Answer 13

-suspension is when material is suspended and carried by a body of water

Question 14

What is longshore drift?

Answer 14

• waves approach the shore in a diagonal direction depending on the dominant wind
• LSD occurs when waves approx the shore at an angle
• material is pushed up the beach by swash at the same direction as the prevailing wind
• waves run back down the beach, backwash drags the material down the steepest gradient perpendicular back down the beach towards gravity
• sediment moves in a zig zag fashion overtime

Question 15

What are the 6 sub-aerial weather in processes?

Answer 15

Frost shattering 
Salt crystallisation 
Wetting and drying 
Solution 
Biological action 
Chemical weathering

Question 16

What is frost shattering?

Answer 16

• it is promoted by the presence of large amounts of water and the tendency for coastal rocks to be severely cracked by the process.
• repeated freezing and melting creates expansion and exerts pressure in the rock widening the crack

Question 17

What salt crystallisation?

Answer 17

-in Tidal or wave splash zone, salt water is readily available and evaporation leads to the formation of salt crystals. As these crystals grow they exert pressures within the rock causing it to gradually break apart

Question 18

What is wetting and drying?

Answer 18

• active in tidal or splash zone
• Clays and shales are present they are prone to expansion and contraction associated with wetting and drying (wet=expand, dry=contacts)= cracks form in the rock

Question 19

What is solution? Weathering

Answer 19

-involving the dissolving of soluble minerals is an active process at the coast. Enlarge joints in the rocks creating pitted and jagged rock surfaces

Question 20

What is biological action?

Answer 20

• shellfish have paddocks, adapted shell to enable them to drill into rock
• they protect the rock surface from wave action but could be removed by storm waves
• seaweed attaches to rock and swaying seaweed may prise loose rocks from sea floor
• blue-green algae secrete chemicals promoting solution

Question 21

What is chemical weathering?

Answer 21

-occurs where there is alternate wetting and drying towards the bottom of slopes where material and moisture often accumulate

Question 22

What are human sub-aerial processes which increase erosion?

Answer 22

• walkers along cliffs cause vegetation and soil to be worn away which contributes to rockfall
• footpaths are heavily used and eroded
• trampling exposes vegetation more readily weathered and eroded
• pressure of cliff tops due to building and removal of protective beach material increases coastal erosion

Question 23

What is mass movement?

Answer 23

Non marine erosion process where the mass downhill movement of material under several influences

Question 24

What are the 7 types of mass movement?

Answer 24

• landslides
• rockfalls
• mudflows
• slides and slumps
• soil creep
• run off
• solifluction

Question 25

What is a landslide?

Answer 25

-mass movement of material (rocks, earth and debris) down hill following lubrication of the foundations

Question 26

What are rockfalls?

Answer 26

-fragment of rock detached by sliding or falling along a vertical cliff

Question 27

What are mudflows?

Answer 27

-heavy rain can cause large quantities of fine material to flow downhill due to soil becoming saturated and excess water cannot infiltrate soil so, surface layers become fluid and flow downhill

Question 28

What are slides and slumps?

Answer 28

A slump is a type of mass wasting that results in the sliding of coherent rock material along a curved surface. A slump is sometimes referred to as a rotational slide because a portion or block of the slope ‘slides’ down as it ‘rotates’ around an axis parallel to the slope.

Question 29

What is soil creep?

Answer 29

Slow downward progression of individual soil particles down a low grade slope

Question 30

What is runoff?

Answer 30

Flowing into a storm water drain

Question 31

What is solifluction?

Answer 31

Movement of wet soil down a slope especially in cold weather conditions

Question 32

What are the 5 types of chemical weathering?

Answer 32

• oxidation
• hydration
• hydrolysis
• carbonation
• solution

Question 33

What is oxidation?

Answer 33

The process of addition and combination of oxygen to minerals. The absorption is usually from O2 dissolved in soil water and that present in atmosphere. The oxidation is more active in the presence of moisture and results in hydrated oxides. Minerals containing Fe and Mg.

Question 34

What is hydration?

Answer 34

Chemical combination of water molecules with a particular substance or mineral leading to a change in structure.

Question 35

Why is hydrolysis?

Answer 35

Mildly acidic water reacts or combines with minerals to make clays and dissolved salts. Degrades rock making it susceptible to further erosion

Question 36

What is carbonation?

Answer 36

Carbon dioxide when dissolved in water it forms carbonic acid.

2H2O + CO2 -> H2CO3
This carbonic acid attacks many rocks and minerals and brings them into solution. The carbonated water has an etching effect up on some rocks, especially lime stone. The removal of cement that holds sand particles together leads to their disintegration.

Question 37

What is solution?

Answer 37

Some substances present in the rocks are directly soluble in water. The soluble substances are removed by the continuous action of water and the rock no longer remains solid and form holes, rills or rough surface and ultimately falls into pieces or decomposes. The action is considerably increased when the water is acidified by the dissolution of organic and inorganic acids.