- The movement of the coast inland due to erosion.
- Lithology is the most important factor in how fast erosion occurs.
Geology:
- Soft rock erodes quickly, hard rock erodes slowly as it has many structural weaknesses such as more joints, faults and cracks
- Hardest to softest rock in order: Igneous, metamorphic, least hard and weak structure
- Unconsolidated material is the softest but erodes the fastest and is the least stable.
- Igneous is very hard rock with fewer faults and cracks.
- Metamorphic is hard rock but it has weaknesses due to folding
- Softer the geology = a fast recession rate because there are more weaknesses in the rock
- Holderness Coast has a very fast recession rate where the geology is boulder clay (unconsolidated material) and slower where chalk (more resistant lithology)
Differential
Erosion – Permeable/Impermeable:
- When erosion occurs at different rates
- Weak strata and permeability leads to faster erosion.
- Permeable geology with different strata with softer layers = less stable and recede faster.
- Permeable: Water can soak through the geology
- Sand is not permeable, boulder clay is a bit and granite is not at all.
- Rain soaks into cliffs adding weight, reducing the strength of the cliff leading to a collapse which increased the rate of recession.
Differential
Erosion – Resistant/Less Resistant:
- Varying resistance of strata can change recession rates and cliff profiles
- Weak strata causes differential erosion undercutting the cliff will fall more quickly. The slight dip towards the sea means rocks can fall off easily.
- Strong geology means strata is weak and hard rock with little differential erosion. The dip towards the land means blocks of rock don’t fall easily.
Vegetation:
- Sand dunes form on sandy coastlines
- Vegetation like grass is very important to stabilise sand dunes as it allows them to become fixed and less easily eroded.
- Salt marshes form estuaries areas where the river meets the sea
- Grass is important to help reduce salt marshes and to make sediments stablise.
- Both landscapes help reduce erosion/recession flooding and help to protect the coast.
Salt
Marsh Succession:
- The succession process forms salt marshes and sand dunes covered in vegetation.
- This reduces the recession rate of the coast as the soils and sand are bound by plant roots. This reduces erosion from waves, wind and weathering. Also, it reduces slumping of soils and the amount of water entering the ground. This reduces recession.
- Sand dunes occur on sandy coasts
- Salt marshes occur around estuaries
- Both have vegetation that develops (succession) e.g. from grasses to bushes
- This protects the coast and reduces recession