Coastal Processes

Question 0

How are waves created?

Answer 0

• By the transfer of energy from the wind blowing over the surface of the water.
• largest waves are formed when winds are:
• very strong
• Blow for long period
• cross large expanses of water.

Question 1

What is a coast?

Answer 1

• a coast is the narrow contact zone between land and sea. it is constantly changing due to land, air and marine processes.

Question 2

what is a fetch?

Answer 2

• it is the maximum distance over water which winds can blow.

Question 3

Describe how does a wave move?

Answer 3

• wate particles moves in a circular orbit.
• particles tend to move up and down.
• only the shape and energy of the wave move sideways.
• in shallow water, the base of the wave slows down due to friction.
• this change the circular orbit to more elliptical.
• the top of the wave becomes higher and steeper.
• the waves top toppels over.
• they water that moves up the beach is called the swash.
• the water that moves back to the ocean is called the backwash.

Question 4

Name the two types of waves.

Answer 4

1. constructive.

2. destructive.

Question 5

describe a constructive wave.

Answer 5

• has limited energy and most energy is used to transport material up the beach with the swash.
• weak back wash, little material carried back to sea.
• thus build up of sediments at low tide.
• do not do much erosion.
• waves are flat and low.
• they occur on flat, wide sandy beaches.

Question 6

Describe a destructive wave.

Answer 6

• it has much more energy and most energy is used by the back wash.
• it transports alot of materials with the back wash.
• these wave are tall and steep.
• short distances between them.
• erode the shore line.
• breaks on steep slope and full force of wave is spent on small area.

Question 7

Name and explain the Processes of marine erosion.

Answer 7

1. corrasion - Large waves hurling sand and stones against a cliff to scour the rocks.
2. attrition - when waves cause rocks and boulders on the beach to bump into each other and break themselves.
3. corrosion - When salts and other acids dissolve a cliff.
4. hydralic pressure - when the sheer force of waves compresses air in cracks in a cliff.
5. Wave pounding - when the sheer force of the waves breaks against the cliff.

Question 8

Explain the process of longshore drift. ( you should be able to draw it )

Answer 8

• when prevailing winds blow at an angle to the shore, it will cause waves to approach and strike the sore at an angle.
• swash will also move at an angle up the beach.
• force of gravity will pull swash directly down the beach.
• Next wave will collect swash and send it up the beach at and angle again.
• process is repeated all along the beach.
• eroded material will move along the beach.
• this movement is called longshore drift.
• to control longshore drift, wall-like structures called groynes, are built at an angel up the beach.

Question 9

How do penisulas form?

Answer 9

• Coatline is made of alternate of resistant and less-resistant rocks.
• the softer materials are eroded away and forms bays.
• the harder materials resist erosion and forms headlands.
• they headlands have deeper water and wave will crash full force against the penisulas.
• the bays has weaker waves because of shallower water.
• the wave will deposit the eroded materials from the headlands at the bays and beaches will form.

Question 10

Name the Landforms created by marine erosion.

Answer 10

1. wave- cut notch.
2. wave - cut platform
3. caves, arches and stacks.

Question 11

what is a wave-cut notch?

Answer 11

• foot of cliff is undercut by waves which overtime will deepen and eventually the cliff will collapse. this is how the cliff retreats.

Question 12

what is a wave- cut plantform?

Answer 12

• retreating cliff leaves behind gentle sloping platform of rock.
• this is where the cliff once stood.
• it is called a wave- cut platform.
• will be exposed during low tide and will be covered during high tide.

Question 13

how are caves, arches and stacks formed?

Answer 13

• withing resistant rock( cliffs ) there can be places of weakness.
• corrasion, hydralic action by waves will widen such a weakness to from a cave.
• if cave was formed in headland, it can be widened until it is cut through to form a natural arch.
• waves will keep eroding the foot untill to weak to support and collaps.
• this leaves a stack.
• further erosion lets stack fall and leaves stump.

Question 14

Name three depositional features.

Answer 14

• Spit
• tombolo
• bar

Question 15

Describe what is and how a spit forms.

Answer 15

• it is a permanent landform.
• it is a long, narrow accumulation of sand with one end attached to the land.
• the other end projects at an angle into the sea.
• may have a hooked end.

FORMS:

• Where prevailing wind and longshore drift move large amounts of sand along the coast.
• when coastline suddenly change direction, sand is deposited there.
• overtime it will form the spit, salt marshes is likely to develop in the sheltered water behind spit.

Question 16

What is a bar?

Answer 16

• it is a spit with both ends conneted to the headlands.

- a lagoon may form behind the bar.

Question 17

What is a Tombolo?

Answer 17

• It is a strech of beach material that connects an island to the main-land.