3.2.4

Subaerial Processes

Test yourself

Processes of Weathering

Weathering describes the breaking down of rocks where they are. Mechanical, chemical and biological weathering are the three main processes.

Illustrative background for Mechanical weatheringIllustrative background for Mechanical weathering ?? "content

Mechanical weathering

  • Mechanical weathering is when rocks are broken down without their chemical composition being changed.
  • Salt weathering is the main type of mechanical weathering affecting coasts:
    • Seawater gets into cracks in rocks.
    • Salt crystals form when the seawater evaporates. These crystals then expand and put pressure on the rock.
    • Over time, the repeated evaporation of saltwater widens the cracks in the rock so much that the rock breaks apart.
Illustrative background for Chemical weatheringIllustrative background for Chemical weathering ?? "content

Chemical weathering

  • Chemical weathering is when rocks are broken down because of their chemical composition being changed.
  • Carbonation weathering is a type of chemical weathering that takes place when it is warm and wet:
    • Carbon dioxide dissolves in rain, making it a weak carbonic acid.
    • The acidic rainwater dissolves types of rock that contain calcium carbonate.
Illustrative background for Biological weatheringIllustrative background for Biological weathering ?? "content

Biological weathering

  • Biological weathering is when rocks are broken down by living things.
    • E.g. plant roots can weather rocks by getting into cracks and pushing them apart as they grow.
    • E.g. Algae can cause the breakdown of rocks from the release of chemicals.
  • The activity of animals near the coast is also an example of biological weathering.
    • E.g. some animals scrap and secrete acid on the rock, like the Piddock shells.

Mass Movement

Mass movement describes when rocks and loose material shift down slopes. This happens when gravity overcomes the force supporting the material. Mass movements can cause rapid coastal retreat and are common when the material is saturated.

Illustrative background for SlidesIllustrative background for Slides ?? "content

Slides

  • Slides are when material moves down a slope in a straight line.
Illustrative background for SlumpsIllustrative background for Slumps ?? "content

Slumps

  • Slumps are when material moves down a slope with a rotation.
  • Slumps happen slower than rockfalls and often happen when unstable permeable rock overlays more stable impermeable rock.
  • A combination of heavy rainfall and erosion processes cause the rotational movement of the cliff.
Illustrative background for RockfallsIllustrative background for Rockfalls ?? "content

Rockfalls

  • Rockfalls are when material breaks apart because of erosion and weathering and then rolls down a slope.
  • The fallen fragments at the base of the cliff create talus scree slopes.

Jump to other topics

1Tectonic Processes & Hazards

2Option 2A: Glaciated Landscapes & Change

3Option 2B: Coastal Landscapes & Change

4Globalisation

5Option 4A: Regenerating Places

6Option 4B: Diverse Places

7The Water Cycle & Water Insecurity (A2 only)

8The Carbon Cycle & Energy Security (A2 only)

9Superpowers (A2 only)

10Option 8A: Health & Human Rights (A2 only)

11Option 8B: Migration & Identity (A2 only)

Go student ad image

Unlock your full potential with GoStudent tutoring

  • Affordable 1:1 tutoring from the comfort of your home

  • Tutors are matched to your specific learning needs

  • 30+ school subjects covered

Book a free trial lesson