Coastal Processes Flashcards
Marine processes
ARE caused by sea
Erosion, transportation and deposition
Sub-aerial processes
Aren’t directly caused by the sea
(Land based)
(Weathering, runoff and mass movement)
Positive Feedback in Weathering
Rate of debris removal exceeds the rate of weathering/mass movements
POSITIVE FEEDBACK as the rate of weathering/mass movement could increase
Negative Feedback in Weathering
Debris removal is slow and ineffective, leads to a build up of debris that reduces the exposure of the cliff face
NEGATIVE FEEDBACK as the weathering/mass movement rate will decrease further
Mass Movement
The downhill movement of weathered material under the force of gravity
When is a mass movement most likely to occur?
When cliffs are undercut by wave action - this causes an unsupported overhang, which is likely to collapse
Types of mass movement?
- Landslides (straight line)
- Slumps (with rotation)
- Rockfalls (breaks up and falls)
- Mudflows (downslope)
- Soil Creep
Landslides
Rate: usually rapid
Wet/Dry: both
Movement: slide
Slumps
Rate: usually rapid
Wet/Dry: both
Movement: slide
Rockfalls
Rate: rapid
Wet/Dry: dry
Movement: fall
Mudflows
Rate: often quite rapid
Wet/Dry: wet
Movement: flow
Soil creep
Rate: imperceptible
Wet/Dry: wet
Movement: creep
Unconsolidated rocks are prone to collapse as there’s little ________ between the _________ to hold them together
Friction
Particles
________ ______ can saturate unconsolidated rock, further reducing ________ and making it more likely to ___________
Heavy rain
Friction
Collapse
________ (the flow of water over the land) can ________ fine particles and transport they downslope
Runoff
Erode
Sub-aerial weathering is the ________ break down of _____ by agents such as…
Gradual
Rock
Ice
Salt
Plant roots
Acids
Weathering…
Weakens cliffs and makes them more vulnerable to erosion
Biological Weathering
The breakdown of rocks by organic activity is biological weathering
Biological weathering (3)
– Plant roots grow into cracks (cracks grow) as roots widen
– Water running through decaying vegetation becomes acidic
– Birds and animals dig burrows into cliffs (puffins and rabbits)
Chemical weathering
Involves a chemical reaction where salts may be dissolved or a claylike deposit may result (easily eroded)
Chemical weathering (3)
– Carbonation (rainwater absorbs C02 = weak carbonic acid) reacts with CaCO to form calcium bicarbonate - easily eroded
– Oxidation (rock minerals - e.g. iron —> rust)
– Solution (Dissolving of rock minerals)
Physical weathering
Involves the break up of rocks without any chemical changes taking place
Physical weathering (3)
– Freeze thaw weathering (water increases in volume by 10%)
– Salt weathering (salty water enters cracks in rock at high tide, water evaporates forming salt crystals which exert pressure on rock as they form)
– Wetting and drying (rocks containing clay expand when wet and this pressure exerted breaks fragments off the rock)
Processes of erosion (6)
Abrasion Hydraulic action Cavitation Wave quarrying Solution Attrition
