Weathering and Mass movement

Weathering and Mass movement

1. Weathering

   • Processes that erode cliffs at their top and face are called weathering processes or sub-aerial weathering processes
   • Physical/mechanical weathering
     • Breaks into smaller pieces
     • Freeze thaw
       • Water fills a crack in a rock and freezes, it will expand and create a strain on the rock. A result of this process repeating over and over causes the rock to break
     • Salt crystallisation
       • When salt water fills a crack in a rock. When the water evaporats the salt crystals are left behind and over time they build up, separating the rock and eventually splitting it.
   • Chemical weathering
     • Break down into component parts
     • Carbonation
       • Rain water is naturally acidic and the acids often react with the chemicals in rock. It is affective against rock with a high calcium carbonate content like limestone.
     • Rust
       • When water causes metals (e.g. Iron) to rust
     • Hydration
       • Rocks with a high clay content are capable of absorbing water. This causes them to swell and eventually break into separate elements.
     • Hydrolysis
       • When hydrogen in rocks react with water, causing the minerals to chemically break down
   • Biological weathering
     • Carried out by living organisms
     • Combination of both physical and chemical weathering
     • E.g. Rabbits physically eroding rocks when burrowning. Excretions chemically erode rocks

2. Mass Movement

   • Rock slides
     • Chunks/slabs of rock break awaty from the cliff. They could be layers of surface rock that slide down the cliff face.
   • Rock falls
     • Rocks break and fall off of a cliff due to freeze-thaw
   • Slumps
     • Typically occurs after heavy periods of rainfall. The top layer of the cliff face becomes saturated with rainwater, and as a result of the water logging it can't support its own weight and the whole section of material slides off
   • Downward movement of weathered rock under the influence of gravity