Subaerial Processes Flashcards
Processes of weathering
Weathering describes the breaking down of rocks where they are
Mechanical, chemical, biological weathering = 3 main processes
Mechanical weathering
When rocks are broken down w/o their chemical composition being changed
Salt weathering = main type of mechanical weathering affecting coasts:
- seawater gets into cracks in rocks
- salt crystals form when the seawater evaporates
These crystals then expand + put pressure on the rock
- over time the repeated evaporation of saltwater widens the cracks = rock so much that the rock breaks apart
Chemical weathering
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’s wet + warm:
- carbon dioxide dissolved in rain making it a weak carbonic acid
- acidic rainwater dissolves types of rock that contain calcium carbonate
Biological weathering
When rocks are broken down by living things
E.g. plant roots can weather rocks by getting into cracks + pushing them apart as they grow
E.g. algae can cause the breakdown of rocks from the release of chemicals
Activity of animals near the coast is also an example of biological weathering
E.g. some animals scrap + secrete acid on the rock
Mass movement
Describes when rocks + loose material shift down slopes
Happens when gravity overcomes the force supporting the material
Mass movement can cause rapid coastal retreat + are common when the material is saturated
Slides
Are when material moves down a slope in a straight line
Slumps
When material moves down a slope with a rotation
Slums happen slower than rockfalls + often happen when unstable permeable rock overlays more stab,e impermeable rock
Combo of heavy rainfall + erosion processes cause the rotational movement of the cliffs
Rockfalls
Are when material breaks apart because of erosion + weathering + then rolls down a slope
Fallen fragments at the base of the cliff create talus scree slopes
