Coastal land processes in the UK (WJEC Eduqas GCSE Geography B): Revision Note

Specification links

The notes on this page cover part 2.1.1 of the WJEC Eduqas B specification - How do people and processes contribute to the development of distinctive coastal landscapes in the UK?

• Geomorphological processes must include weathering and mass movement.

Coastal geomorphic process

• The coast is the area where land and sea meet

• A geomorphic process is any natural action that alters the shape of the Earth's surface and includes:

  • weathering

  • erosion

  • mass movement

  • transportation

  • deposition

• Coastal geomorphological processes are divided into two parts:

  • Terrestrial processes: those that occur onshore and are land-based

    • Also known as subaerial weathering, it describes coastal processes that are not linked to the action of the sea

  • Marine processes: those that occur offshore and are water-based

Weathering and the coast

What is weathering?

• Weathering is the breakdown of rock in situ

  • It does not involve the movement of material, making it different from erosion

• Weathering weakens cliffs and makes them more vulnerable to erosion

Types of weathering

• There are three types of subaerial weathering: mechanical, chemical, and biological.

• Mechanical weathering physically breaks up rock

  • Freeze-thaw or frost shattering is where:

    •  Water enters cracks and joints in the rock

    •  As the water freezes, it expands, causing the cracks to open wider

    • As the water thaws, the crack shrinks, easing the pressure on it

    •  Repeated freezing and thawing over time widens the crack, causing pieces of rock to split off the cliff face

    • Big boulders break into smaller rocks and gravel

• Chemical weathering occurs when rocks are broken down by a chemical process:

  • Rainwater is slightly acidic due to 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

• Biological weathering is when living organisms wear rocks away:

  • 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 prises the rock apart

  • Burrowing animals, such as rabbits, disturb the ground above the burrow, which puts pressure on any cracks, eventually leading to pieces falling off the rock

Mass movement and the coast

• Mass movement is the downhill movement of material under the influence of gravity

• Heavy rain can also make cliffs less stable and make mass movement more likely through throughflow and runoff

• It includes landslides, slumping and rockfalls

• The following factors determine the type of movement:

  • Angle of slope (the steeper the slope, the faster the movement)

  • Nature of regolith

  • Amount and type of vegetation

  • Water

  • Type and structure of rock

  • Human activity

  • Climate

• Soil Creep:

  • It often occurs in humid areas, moving less than 1 cm each year.

  • Soil expands when it freezes, gets wet, or heats up in the sun

  • The soil expands and lifts at right angles to the slope

  • When the soil shrinks, it drops straight down

  • Soil creep happens slowly as the soil shifts just a millimetre to a few centimetres at a time

• Flow:

  • Happens on slopes from 5° to 15° at speeds of 1 to 15 km per year

  • It usually occurs after the soil gets saturated with water flowing across the surface

  • Flattened vegetation gets carried away with the soil

• Slide:

  • A mass of material moves together until it reaches the bottom of a slope

• Fall:

  • Slopes rise sharply, and movement happens quickly

  • Several reasons caused this.

    • Extreme weathering: Freeze-thaw action loosens rocks, making them unstable and causing collapse

    • Excess rain will soften the surface and cause the slope to collapse

    • Earthquakes dislodge unstable rocks

    • Hot weather dries out soil, causing it to shrink and rocks to fall

• Slump:

  • Typically located on weaker rock types like clay that get saturated and heavy

  • This occurs often at the coast and is called rotational slip

  • A large area of land moves down the slope in one piece

  • It slumps and leaves a curved, indented surface