Coastal Processes: Weathering and Mass Movement
Coastal landscapes are constantly evolving due to various weathering processes and mass movements. Chemical weathering occurs when slightly acidic rainwater dissolves certain types of rocks and minerals, altering their chemical composition. Mechanical weathering, also known as physical weathering, breaks down exposed rock without changing its chemical makeup, often resulting in scree at the base of cliffs.
Biological weathering is caused by the actions of plants and animals. Plant roots can grow into rock cracks, while burrowing animals like rabbits can weaken softer rocks such as sand. Freeze-thaw weathering, a significant type of physical weathering, occurs when water in rock cracks repeatedly freezes and thaws, expanding and contracting to widen cracks and eventually break the rock apart.
Definition: Mass movement is the downslope shifting of rocks and loose materials due to gravity overcoming the forces supporting the slope.
Mass movement is more likely to occur when the material is saturated with water, which acts as a lubricant and increases weight. Various types of mass movement include:
- Rockfall: Rock fragments break away from cliff faces
- Landslide: Blocks of rock slide downhill along a straight plane
- Mudflow: Saturated soil and weak rock flow down a slope
- Slumps (rotational slip): Saturated soil and weak rock rotate along a curved slip plane
Highlight: Mass movement can cause rapid coastal retreat and create steep cuts in slopes called scarps.