Coastal processes

Question 1

What 3 factors does the size and energy of the wave depend on?

Answer 1

the fetch – how far the wave has travelled

the strength of the wind

how long the wind has been blowing for

Question 2

What are the 2 wave types?

Answer 2

Constructive and destructive

Question 3

What is swash and backwash?

Answer 3

When a wave reaches the shore, the water that rushes up the beach is known as the swash. The water that flows back towards the sea is known as the backwash. The energy of the swash and backwash determine the type of wave.

Question 4

What are the characteristics of a destructive wave?

Answer 4

• A weak swash and strong backwash
• occurs in stormy conditions, with strong winds
• the strong backwash removes sediment from the
  beach
• waves that are steep and close together
• tall waves with short wave length
• they arrive quickly and have a high frequency – a lot
  of them come in a short period of time

Question 5

What are the characteristics of a constructive wave?

Answer 5

• a strong swash and weak backwash
• small waves, with low wave height and long wave
  length
• occurs in calm conditions, without much wind
  the strong swash brings sediments to build up the
  beach
• the backwash is not strong enough to remove the
  sediment
• waves that are low and further apart

Question 6

When does freeze-thaw weathering occur?

Answer 6

Freeze-thaw weathering occurs when rocks are porous or permeable.

Question 7

How does freeze-thaw weathering occur?

Answer 7

• Water enters cracks in the rock.
• When temperatures drop, the water freezes and
  expands causing the crack to widen.
• The ice melts and water makes its way deeper into the cracks.
• The process repeats itself until the rock splits entirely.

Question 8

How does biological weathering occur?

Answer 8

• Plant roots can get into small cracks in the rock.
• As the roots grow, the cracks become larger.
• This causes small pieces of rock to break away.

Question 9

How does chemical weathering occur?

Answer 9

Rainwater and sea water can act as weak acids. If a coastline is made up of rocks such as limestone or chalk, over time they can become dissolved by the acid in the water.

Question 10

Define mass movement

Answer 10

Mass movement is the downhill movement of sediment that moves because of gravity.

Question 11

How does rockfall occur?

Answer 11

Bits of rock fall off the cliff face, usually due to freeze-thaw weathering.

Question 12

How does a landslide occur?

Answer 12

Large blocks of rock become detached and slide downhill.

Question 13

What are the 4 types of coastal erosion?

Answer 13

Hydraulic action – air may become trapped in joints and cracks on a cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.
Abrasion – bits of rock and sand in waves grind down cliff surfaces like sandpaper.
Attrition – waves smash rocks and pebbles on the shore into each other, and they break and become smoother.
Solution – acids contained in sea water will dissolve some types of rock such as chalk or limestone.

Question 14

How does transportation at the coast occur?

Answer 14

Sediment is carried by the waves along the coastline. The movement of the material is known as longshore drift. Waves approach the coast at an angle because of the direction of the prevailing wind. The swash will carry the material towards the beach at an angle. The backwash then flows back to the sea, down the slope of the beach. The process repeats itself along the coast in the zig-zag movement.

Question 15

What 4 different ways move beach material?

Answer 15

Solution – when minerals in rocks like chalk and limestone are dissolved in sea water and then carried in solution. The load is not visible.
Suspension – small particles such as silts and clays are suspended in the flow of the water.
Saltation – where small pieces of shingle or large sand grains are bounced along the sea bed.
Traction – where pebbles and larger material are rolled along the sea bed.

Question 16

How does deposition occur?

Answer 16

When the sea loses energy, it drops the material it has been carrying. Deposition can occur on coastlines that have constructive waves.

Question 17

What are the factors leading to deposition?

Answer 17

• waves start to slow down and lose energy
• shallow water
• sheltered areas, eg bays
• little or no wind

Question 18

What key factors affect coastlines?

Answer 18

• The rock type/geology. Hard rock types are less likely to erode.
• The fetch of the wave and the strength of the wind. Powerful winds and a long fetch create the most damaging (erosive) waves.
• The angle of the slope – steep slopes erode more violently and frequently.
• Weather conditions – freezing temperatures and heavy rain increase weathering and the rate of erosion.
• The amount of vegetation – the presence of vegetation helps stabilise slopes but also increases the occurrence of biological weathering.
• The amount of human interference – if there are no man-made structures (eg sea walls) to protect the coast, then the coast is more vulnerable to attack. - However, the construction of houses, industry and other man-made structures in the first instance are the reasons why coastal erosion is a concern.

Question 19

What is longshore drift?

Answer 19

waves transporting material driven along the
coast in the direction of the prevailing wind. This
is the swash. Waves retreat perpendicular to
coastline under gravity. This is the backwash. In
this way material is transported along the
coastline in zig-zag motion.