- Sub-Aerial Processes: Processes that occur under the ground
- Weathering: Breakdown ‘in situ’. Rock and ground are broken up.
- Mass Movement is a large amount of land/rock/soil falling down under gravity e.g a landslide of rocks from a cliff, slumping of clay.
Types
Of Weathering:
- Mechanical Weathering: Breakdown of rocks into smaller pieces by a physical process e.g ice or heat changes
- Chemical Weathering: Dissolving and weakening of rocks by chemical or solution e.g acidic water. Affects mainly sedimentary chalk, and limestone.
- Biological Weathering: Weakening of material due to living organisms like shellfish boring holes into rocks and rabbits digging burrows in sand dunes.
Mass
Movement:
- Landslides: The movement of downhill of rocks and soils under the force of gravity.
Influences/Factors
That Control Them:
- Geology/lithology (rock type, hardness and structure)
- Waves (size, frequency, height of backshore)
- Other sub-aerial processes such as weathering and freeze-thaw
Case
Study: Holderness Coast:
- Blockfall: Occurs from hard lithology. Pieces of rock break, fall or topple off especially from steep verticle cliffs with a weak structure (joints, strata). Caused by undercutting waves and sub-aerial processes like freeze-thaw. Creates boulders in the backshore area. Also known as rockfall
- Rotational Slumping: Occur in soft unconsolidated material like boulder clay or soils (weak/soft geology). Landslides are downward under gravity due to wave action and heavy rainfall (makes the ground heavier). Creates a lot of sediment for beaches (clay, silt, sand)
- Also, a huge landslide in California, USA.
Mass
Movement Creating Landforms:
- Mass movement = distinctive coastal landforms (morphology)
- Blockfall/rockfall = (talus) scree slopes
- Rotational slumps = rotational scars
- Talus is the name for landforms made from rock pieces. Talus scree slopes are large triangular shaped landforms beneath rocky cliffs. They form where mechanically weathered rocks have fallen down and piled up. Therefore, this builds up
a large debris fan of the material.
- Rotational slumps occur in unconsolidated material e.g. boulder clay (very soft geology), especially after heavy rain. As the land surface ‘slumps’ down, it leaves stepped land or ‘terraces’. Therefore the cliff profile can be described as terraced. The new exposed steep clay and soil is called a rotational scar or scarp.