coastal processes

Question 1

factors influencing wave energy

Answer 1

1.wind speed
>the faster the wind blows, the greater the wave energy
2.wind duration
>the longer the wind blows, the larger the waves created and greater the wave energy
3.length of fetch
>the greater the fetch,the greater the wave energy

Question 2

movement of waves

Answer 2

open ocean
>waves have a long wavelength and low wave height
>water particles move in a circular orbit
nearing Coast
>base of wave experiences friction with the sea bed and starts to slow down
>wave height increases as wave length decreases
>movement of water particles change to an elliptical orbit
nearest coast
>base of wave stops but wave crest becomes steeper and topples over
>waves break onto coast,releasing energy

Question 3

swash and backwash

Answer 3

swash
>process where water rushes up beach when waves break
>as swash moves up beach,it carries sediments with it
>it brings materials to coast and has a constructive effect on coast

backwash
>return flow of swash when it loses energy due to friction with shore and gravity
>sediments are carried from shore into sea
>it removes materials from sea and has a destructive effect on coast

Question 4

constructive waves

Answer 4

> break far from shore with low wave energy
occurs on gently sloping coasts and sheltered coasts
strong swash but weak backwash
depositional in nature

Question 5

destructive waves

Answer 5

> breaks violently on shore with high wave energy
occurs on steep coastal slopes and open coasts
weak swash but strong backwash
erosional in nature

Question 6

erosion process

Answer 6

hydraulic action
>when waves strike against a rock surface,waves trap air in rock joints or cracks.this air is compressed by oncoming waves,exerting pressure on rock joints.As the air is repeatedly compressed,joints weaken and rocks shatter
abrasion
>as waves break,sediments carried by waves such as rocks and sand are hurled against coast.loosened sediments knock and scrape against coastal cliffs.this weakens
surface and breaks down coast.
>overtime,impact of
abrasion is powerful enough to undercut cliff
attrition
>when rock particles carried by waves rub or hit against each other,they break down into smaller pieces and become smoother and more rounded over time
solution
>sea water reacts chemically with water-soluble minerals in coastal rocks and dissolves them.for example,limestone rocks are easily corroded by carbonic acid
>when solution of minerals occur,rocks are weakened and eventually disintegrate

Question 7

sediments transport

Answer 7

> prevailing winds result in a series of waves approaching coasts at an angle
longshore currents are generated in nearside zone,moving sediments parallel to coast
when waves break on beach, sediments move up the beach at an angle,carried by swash.swash loses energy due to friction and gravity,causing sediments to move perpendicularly down beach by backwash
the combined effects if sediments movement by beach drift and longshore current is known as longshore drift.

Question 8

formation of beach

Answer 8

1. stronger swash carries and deposits sediments up beach
2. swash loses energy due to friction with shore and deposits sediments
3. as backwash is weaker,little erosion occurs.finer,lighter sediments are carried and deposited near waters edge by backwash