Costal processes

Question 1

What are the 2 categories of costal processes?

Answer 1

Marine processes - offshore (water-based)
Terrestrial processes - onshore (land-based)

Question 2

Name the 5 different processes

Answer 2

Wave action
Erosion
Transportation
Weathering
Mass movement

Question 3

How are waves formed?

Answer 3

Waves are formed by wind blowing over the surface of the sea.
The height and strength of waved depend on 3 things:

The fetch
The amount of time the wind blows
The strength of the wind

Question 4

What are the two types of wave?

Answer 4

Destructive waves erode the beach. They have a short wavelength, high frequency rate and a steep wave gradient. Their backwash is stronger than
their swash, which scours the beach, dragging material out to sea
Constructive waves are beach builders. They have a long wavelength, low frequency rate and a shallow wave gradient. The swash is stronger than its
backwash, which carries material up onto the beach and deposits it there

Question 5

What are the methods of erosion?

Answer 5

Hydraulic Action
Attrition
Corrosion
Abrasion

Question 6

What is longshore drift?

Answer 6

It is the main process of deposition and transportation along the coast
Influenced by the prevailing wind, waves approach the beach at an angle
As the waves break, the swash carries material up the beach at the same angle
As the swash dies away, the backwash carries the material down the beach at right
angles (90°)
The process repeats, transporting material along the beach in a zig-zag movement

Question 7

Draw a diagram representing longshore drift

Question 8

What is weathering?

Answer 8

This is the break-down of rock in-situ. Weathering does not involve the movement
of material and this makes it different from erosion

Question 9

What are the 3 types of weathering?

Answer 9

Mechanical
Chemical
Biological

Question 10

Describe a method of mechanical weathering

Answer 10

One example is freeze-thaw or frost shattering
Water gets into cracks and joints in the rock
When the water freezes it expands and the cracks open a little wider
Over time, pieces of rock split off the rock face, whilst big boulders are
broken into smaller rocks and gravel

Question 11

Describe the process of chemical weathering

Answer 11

Rainwater is slightly acidic through absorbing carbon dioxide from the
atmosphere
This reacts with minerals in the rock creating new material
Rock-type affects the rate of weathering e.g. limestone chemically weathers
faster than granite
The warmer the temperature, the faster the chemical reaction

Question 12

Describe a method of biological weathering

Answer 12

Trees and other plants can grow within the cracks in a rock formation
As the roots grow bigger they push open cracks in the rocks making them
wider and deeper
Over time the growing tree eventually prizes the rock apart

Tiny organisms like bacteria, algae and moss can grow on rocks
These produce chemicals that break down the surface layer of the rock

Burrowing animals such as rabbits disturb the ground
This destabilizes the rock above the burrow
Increasing pressure on any cracks
Eventually leading to pieces falling off the rock

Question 13

What is mass movement?

Answer 13

The downhill movement of material under the influence of gravity
Throughflow and runoff caused by heavy rain can also make cliffs more unstable
and increase the likelihood of mass movement
It includes landslides, slumping and rockfalls

Question 14

What influences mass movement ?

Answer 14

Angle of slope (steeper is faster)
Nature of regolith
Amount and type of vegetation
Water
Type and structure of rock
Human activity
Climate

Question 15

What is soil creep?

Answer 15

Speed is below 1cm per year
Common in humid climates
When soil expands, individual particles are lifted up at right angles to the slope
Soil also expands when it freezes, gets wet or is heated up in the sun
When the soil shrinks again, the particles fall straight back down

Question 16

What is flow?

Answer 16

Occurs on slopes between 5° and 15°
Usually after the soil has become saturated with a flow of water across the surface
Vegetation can be flattened and carried away with the soil
Speeds range from 1 to 15km per year

Question 17

What is slide?

Answer 17

A movement of material ‘en masse’ which remains together until hitting the
bottom of a slope

Question 18

What is fall?

Answer 18

Slopes are steep and movement is rapid
Caused by a number of reasons:
Extreme weathering - freeze-thaw action can loosen rocks that become unstable and collapse
Rainfall - too much rain will soften the surface leading to collapse of the slope
Earthquakes can dislodge unstable rocks
Hot weather can dry out soil causing it to shrink and allow rocks to fall

Question 19

What is slump?

Answer 19

Usually found on weaker rock types (i.e. clay), that becomes saturated and heavy
This is common at the coast and is also known as rotational slip
It involves a large area of land moving down the slope in one piece
Due to the nature of the slip it leaves behind a curved surface