Ch 3.2 Coastal Processes

Weathering: The gradual breakdown of rocks in situ (in their original place) at/close to the ground surface.

Types of weathering:

Freeze-thaw; water percolates into cracks/pores, freezes and expands (approx.9%). Expansion exerts stress, causing cracks to widen.

Salt weathering; salt water evaporates in tidal zone, leaving salt crystals.  Crystals grow and exert stress in rock, causing it to break.

Wet/dry cycles; clay-rich rock expands and contracts, forming cracks.

Carbonation; carbonate rock absorbs CO2, water forms weak carbonic acid, reacts with rock, rock dissolves.

Biological; plants prise apart rocks, birds/animals/marine life burrow into cliffs, water becomes acidic when passing through dead vegetation.

Mass Movement: Downhill movement of rock and soil as a response to gravity

Types of mass movement:

Landslide; rapid movement of detached slabs down a slide plane

Rockfall; individual fragments fall from cliff face; freeze-thaw

Mudflow; saturated soils flow downhill, heavy rain

Rotational slip; landslips in weak rock (clay, sand)

Soil creep; very slow downhill movement, rock particles

Marine Erosion:  4 main processes

Hydraulic action; waves breaking against rock

Corrasion; rocks thrown at cliff by sea water, cliff becomes gouged/chipped

Abrasion; "sandpaper" effect of loose rocks against bare rock, surface polished/smooth

Attrition; rocks bash together, they become smaller & smoother

Marine Transportation: 4 main ways sediment is transported

Traction; rolling large/heavy rocks along bed

Saltation; rocks bounced along bed

Suspension; lighter sediment suspended, murky appearance to water

Solution; completely dissolved sediment