The Sea

Question 1

How are waves made?

Answer 1

Waves are formed by wind moving across the surface of the sea. The distance of open sea over which the wind blows is called the fetch. Waves with a greater fetch are stronger.

Question 2

What 2 things does the size of a wave depend on?

Answer 2

The size of the wave depends on 2 things.
1. The strength of the wind.
2. The length of the sea (fetch).

Question 3

Explain the two types of waves.

Answer 3

1. Constructive waves: waves in which the swash is greater than the backwash. Constructive waves deposit material.
2. Destructive waves: waves in which the backwash is greater than the swash. Destructive waves erode material and carry it away.

Question 4

Explain what backwash is.

Answer 4

When the water runs out of speed it stops and it flows back down the beach into the sea. This is called the backwash.

Question 5

Explain what swash is.

Answer 5

As the wave reaches the shore it breaks. The white foamy water that flows up the beach is called the Swash.

Question 6

Briefly explain the 4 processes of coastal erosion.

Answer 6

1. Hydraulic Action – this is the power of the water hitting the coastline.
2. Air Compression – The waves trap air in crack in the rocks. As the waves retreat the trapped air expand quickly and can crack the rock.
3. Abrasion – this is erosion caused by small rocks carried in the sea water hitting against the coastline.
4. Attrition – this is erosion caused by the small stones hitting each other breaking themselves into smaller pieces.

Question 7

Explain the formation of any landform of coastal erosion with the aid of a labelled diagram.

Answer 7

Bays and Headlands
• The coastline is made up of hard rock and soft rock. As waves crash against the coastline, soft rock such as limestone is eroded faster than hard rock such as basalt.
• The processes of hydraulic action, abrasion, compression and, sometimes, solution erode the softer rock to form a bay.
• The harder rock stands out on either side of the bay to form headlands.
• Sometimes beaches form in bays.
Example of a bay: Dublin Bay.

Question 8

Briefly explain longshore drifts.

Answer 8

Longshore drift moves material along the beach. This occurs when waves approach the beach at an angle. The swash brings material up onto the beach, then the backwash brings it back down to the sea in a straight line. The swash, again moving in at an angle will move the material further across the beach. This process continues and the load is moved along in a zig zag pattern.

Question 9

Explain the formation of any landform of coastal deposition with the aid of a labelled diagram.

Answer 9

• Longshore drift loses its energy and deposits the material it is carrying when it is interrupted by a sheltered bay.
• The material builds up over time and gradually extends across the bay. A sand spit is formed.
• As the sand spit increases in size, vegetation grows on it and a beach can form on the side facing out to sea.
• The end of the spit is often curved due to the current.
Example: Rossbeigh Strand near Glenbeigh, Co. Kerry.

Question 10

List 4 things the sea provide humans with.

Answer 10

The sea provides us with:
1. energy (oil, gas, wave power)
2. leisure activities,
3. transport routes,
4. food.

Question 11

Briefly explain 3 ways people can control the destructive power of the sea.

Answer 11

1. Sea Walls – Sea walls are concrete walls with a curved top on them which helps to deflect the waves back out to sea. E.g. Tramore
2. Boulders – Large rocks are placed at the base of cliffs or in front of sand dunes. It prevents erosion by reducing the power of the waves. E.g. Tramore
3. Groynes – Groynes are low walls built of wood. They are built at right angles to the shore to help prevent sand being moved along the beach by Longshore Drift. E.g. Rosslare