Coasts GW1

Question 1

How do waves affect coastal environments?

Answer 1

Destructive waves will lead to erosion, while constructive waves will lead to deposition.

Question 2

How are headlands and bays formed?

Answer 2

1. The coastline has bands of less resistant and more resistant rock that alternate.
2. Less resistant rocks will erode faster than more resistant rock.
3. The less resistant rock will erode away to form wide indented coasts, called bays.
4. The more resistant rock extend into the sea as they erode less. These are known as headlands.

Question 3

How are waves generated?

Answer 3

Waves are generated when energy from wind blowing across seas and oceans is transferred to the water surface. Therefore, factors affecting wind energy also affect the energy of waves.

Question 4

what are the factors affecting wave energy?

Answer 4

there are 3 factors: fetch, wind speed and wind duration.

Question 5

how does wind speed affect wave energy?

Answer 5

the faster the wind blows, the greater the wave energy is.

Question 6

how does the wind duration affect wave energy?

Answer 6

the longer the wind blows, the larger the waves are; resulting in greater wave energy.

Question 7

how does fetch affect wave energy?

Answer 7

the greater the fetch, the more energy the waves have as the wind would have passed through a larger body of water.

Question 8

Explain the different coastal erosional processes.

Answer 8

(a) Hydraulic action
When waves strike against a rock surface, the waves trap air in the rock joints. The air is compressed by the oncoming waves, exerting pressure on the joints. As the air is repeatedly compressed, the joints weaken and the rocks shatter.
(b) Abrasion
As waves break, sediments carried by waves such as sand and rocks are hurled against the coast. The loosened sediments knock and scrape against the coastal cliffs. This weakens the surface and breaks down the coast. Overtime, the impact from abrasion is powerful enough to to undercut a cliff.
(c) Attrition
When rock particles carried by waves rub or hit against one another, they break down into smaller pieces and become smoother and more rounded over time.
(d) Solution
Sea water reacts chemically with water-soluble minerals in coastal rocks and dissolves them. For example, limestone rocks are easily eroded by carbonic acid. When solution of minerals occurs, rocks are weakened and eventually disintegrate.

Question 9

what is the definition of coasts

Answer 9

the area where the land meets the sea

Question 10

coastal environments are dynamic and changing due to?

Answer 10

waves 
currents 
tides 
geology 
human activities 
ecosystem type: mangrove and coral

Question 11

What are cliffs and shore platforms?

Answer 11

A cliff is a high steep rock face along the coast.

A shore platform is a gently sloping expanse of rock sediments/debris at the base of a cliff resulting from erosion.

Question 12

How are spits and tombolos formed?

Answer 12

1. Some coasts will have an abrupt change in the direction of the coastline.
2. Longshore drift will continue to transport materials in the original direction for sometime.
3. Longshore drift deposits materials in the sea where they accumulate over time.
4. The accumulated materials eventually appear above the surface of the water, forming a spit.
5. If the spit connects an offshore island with the mainland or another island, it is called a tombolo.

Question 13

How are cliffs and shore platforms formed?

Answer 13

1. The waves repeatedly pound against a rocky coast. This weakens the rock and causes lines of weakness to be formed in the rock surface.
2. Hydraulic action and abrasion may erode a crack/lines of weaknesses/joints to form a notch.
3. As erosion proceeds, the notch is deepened to form a bigger, hollow space called a cave.
4. Further erosion by the waves eventually causes the roof of the cave to collapse and forms a cliff.
5. As the erosion continues, an overhanging cliff is formed. Eventually, this overhanging cliff will collapse and materials will be deposited at the foot of the cliff. Some of these materials may be carried by waves and then are thrown against the base of the cliff causing further erosion.
6. Overtime, the cliff will retreat inland and a gentle sloping platform appears at the base of where the cliff used to be. It is called a shore platform and it is submerged during high tide.

Question 14

what are currents and how do they affect coastal environments

Answer 14

currents are large-scale continuous movements of water in seas and oceans, driven largely by prevailing winds which generally blow in one direction.

Currents carry large amounts of energy and shape coasts through the processes of coastal erosion, sediment transport and sediment deposition.

Closer to the shore, nearshore currents help to shape the coastline, an example is longshore currents which flow parallel to the coast

Question 15

What are caves, arches and stacks?

Answer 15

Cave - a big, hollow space

Arches - a bridge of rock

Stacks - a pillar of rock in the sea left behind after an arch collapses

Question 16

what are tides and how do they affect coastal environments?

Answer 16

tides refer to the daily alternate rising and falling of the sea level seen along the coasts, caused by the gravitational pull of the moon and the sun on the earth. Each coastal area receives two high tides and two low tides daily which has significant impacts on the coast.

At high tides the waves erode and transport more sediments away from the larger parts of the coasts than at other times.

Areas located between low and high tides will have more weathering and erosion than areas constantly submerged in water

Question 17

what is geology and how does it affect coastal environments?

Answer 17

geology is the arrangement and composition of rock found in the area. Rocks may be arranged in layers such as in alternate layers of hard and soft rock. More resistant rocks like granite and basalt will erode slower as compared to less resistant rocks like limestone. Coastal processes that operate on coasts consisting of different types of rock result in coasts with different coastlines

Question 18

what are human activities and how do they impact coastal environments

Answer 18

some examples of human activities are living, trading, fishing and engaging in recreational activities in these environments. People alter coastlines when they build marinas and port facilities and many more. They also cause pollution in these environments by dumping waste into the water

Question 19

How are caves, headlands and stacks formed?

Answer 19

1. Within headlands, some rocks may be less resistant to erosion than other rocks. These parts of the headlands will be eroded more quickly, especially by hydraulic action and abrasion. Waves attack lines of weaknesses (such as joints & faults) at the base of the headland and undercut it. The continuous action of waves forms a cave at the area that is hollowed by the wave action.
2. Caves may develop on each side of the headland. Erosion may eventually join caves together leaving a bridge of rock known as an arch above the opening.
3. After a period of time, the roof of the area may collapse to form a stack. A stack is a pillar of rock in the sea left behind after an arch collapses.

Question 25

Explain wave refraction.

Answer 25

Process by which waves change direction as they approach an uneven coastline.

Waves converge on headlands, increasing wave height and erosive energy.

Waves diverge at bays, decreasing wave height and erosive energy.

Occurs because shallower depths of water causes parts of waves to slow down relative to other parts of the wave.

Question 26

Define ‘swash’ and ‘backwash’.

Answer 26

Swash refers to water that rush up a beach after the wave breaks, carrying sediments up the shore.

Backwash refers to the water that returns to the sea after the swash loses energy due to gravity and friction, carrying sediments back into the sea.

Question 27

Describe the type of environments where constructive waves and destructive waves occur at.

Answer 27

Constructive waves: low gradient and low energy environment.

Destructive waves: High energy environment with steep gradient.

Question 28

Explain how sediments move due to transportation.

Answer 28

The movement of sediment happens during beach drift and longshore drift as a result of waves approaching the coast at an angle.
(a) Beach drift
As waves approaching the coast at an angle break on the beach, sediments move up the beach at an angle as swash and move perpendicularly down the beach as backwash. The resultant zigzag movement along the beach is known as beach drift.
(b) Longshore drift
When waves approach the coast at an angle, they generate longshore currents in the nearshore zone and move sediments along the shore. Longshore currents are ocean currents that flow parallel to a coast. The combined effect of sediment movement by longshore currents and beach drift is known as longshore drift. (Longshore drift is most rapid when waves approach a straight coast at an angle of about 30°.

Question 29

Explain why deposition takes place.

Answer 29

(a) Sediments eroded from the coast are transported away and deposited elsewhere. When wave energy decreases, the waves are unable to carry these sediments. Large sediments are deposited first, followed by smaller sediments. Deposited sediments vary in type and size, resulting in a variety of beaches.
(b) The location of coasts influences the deposition of sediments. In areas where coasts are sheltered from strong winds, destructive waves are less common. Fine sediments are deposited along sheltered coasts with calm waters such as mangrove coasts. In deep bays sheltered by headlands. On the other hand, coarser sediments are likely to settle in more exposed areas where there is higher wave energy to remove the finer sediments.

Question 30

Explain how beaches form.

Answer 30

Different rates of erosion form different sediment sizes.

When there is a drop in the energy of the waves, the materials will be deposited along the coast. Overtime, a beach will be formed.