HYDRAULIC ACTION: waves enter faults in coastline, compressing the air within. when the wave retreats the air expands quickly causing a minor explosion.
ABRASION: waves throw particles against the rock at high velocity.
ATTRITION: material carried by waves bumping into each other becoming smoothed and broken down into smaller pieces.
SOLUTION: chemical action of the seawater (contains carbonic acid) the acids slowly dissolve rocks along the coastline, particularly alkaline rocks like limestone and chalk.
SUSPENSION: tiny particles of sediment carried (in suspension) in the sea's currents.
SALTATION: smaller stones/pebbles picked up and dropped, results in skipping motion
SOLUTION: dissolved chemicals carried along
TRACTION: large stones/boulders rolled along the seabed
- waves approach shore at an angle
- material pushed up beach by swash (same direction as approach)
- backwash drags material down steepest gradient at right angles to shoreline
- over period of time sediment moved in zigzag motion down coast by saltation and traction
- if material carried for a while it becomes smaller, more rounded and better sorted
- deposition of this material then occurs in sheltered areas or where direction of coastline changes abruptly
FREEZE-THAW: process whereby water repeatedly freezes and melts within joints/faults in the rock. As water percolates into the faults it freezes causing expansion (by up to 9%) putting presure on the rock. Scree breaks off at bare and rocky cliffs.
BIOLOGICAL: weathering resulting from organic agents (eg tree roots/rabbit burrows etc). Plants can prise apart rocks (with their roots) causing them to crack. Animals like piddocks (like clams) also burrow into the rock.
CHEMICAL: weathering of rocks by chemicals. CaCO3 in rocks like limestone dissolved by water and CO2 in air reacting (forms carbonic acid)
SALT: physical weathing of rocks. Salt crystals left behind after seawater evapourates. Can grow over time and cause cracks to form (like ice).
SOIL CREEP: (slowest form of m.m.) Heavy rain, freeze-thaw weathering and long wet periods can all move the soil in a net downslope movement of less than 1cm a year.
LANDSLIDE: rapid movement of detached slabs of rock down the cliff face
MUDFLOWS: faster movements occur on steeper slopes which are saturated (with water). Fast, most likely to be found on unconsolidated material after heavy rainfall.
ROTATIONAL SLIP: common coastal landslips in weak rocks, eg. sands and clays
ROCKFALL: rapid movements found where slopes exceed 40 degrees. Indivual rocks fall off a cliff face (often due to freeze-thaw)