Coast Gateway 1

Question 1

Coastal erosion

Answer 1

• hydraulic action
• abrasion
• solution
• attrition

Question 2

Hydraulic Action

Answer 2

1. When waves strike against rock surface, air is trapped in rock joints
2. Air is compressed repeatedly by oncoming waves, exerting pressure on joints
3. Joints are weakened and shatter

Question 3

Abrasion

Answer 3

1. Waves carry sediments such as sand and rocks which are hurled against the coast when waves break
2. These sediments knock and scrape against the coastal cliff surface
3. This weakens the surface and coast breaks down
4. Overtime, impact can be powerful enough to undercut a cliff

Question 4

Solution

Answer 4

1. Seawater reacts chemically with and dissolves water soluble minerals in rocks
2. Rocks are weakened and eventually disintegrate
3. Carbonic acid easily corrodes limestone rocks

Question 5

Attrition

Answer 5

1. Sediments such as rocks carried by waves rub and hit against each other
2. Rocks break down into smaller pieces
3. Overtime, rocks become rounder and smoother

Question 6

Sediment transport

Answer 6

1. Involves 2 processes, beach drift and longshore drift
2. These 2 processes resulted from waves approaching coast at an angle

Beach drift

1. When waves approach coast at an angle
2. Waves break on shore
3. Swash carry sediments up the beach at an angle
4. Backwash carry sediments perpedicularly down the beach
5. The resultant zig zag movement of sediment is beach drift

Longshore drift

1. It is the combined effect of both beach drift and longshore current
2. When waves approach coast at an angle
3. Longshore currents are generated in offshore zone near shore and carry sediments along shore
4. Longshore currents are currents flowing parallel to the coast
5. It is most rapid when approach coast at 30 deg

Question 7

Sediment deposition

Answer 7

1. It involves the addition of materials onto beach, building it up
2. When wave energy decrease, waves can no longer carry sediments
3. Coarser sediments are deposited first before finer sediments
4. Deposited sediments vary in types and sizes resulting in a variety of beaches
5. Location of coasts affect the deposition of sand

Finer sediments are deposited in sheltered coasts of calm waters where destructive waves are less common and sheltered from strong winds
- sandy beaches often found in deep bays sheltered by headlands

Coarser sediments are deposited in more exposed coasts where wave energy is higher to remove finer sediments