Coastal processes Flashcards
What are sub-aerial processes
Land-based processes which alter the shape of a coastline.
What is weathering
Breakdown of rock in situ
What is Physical weathering
Disintegration, eg the break up of rock first into larger blocks and eventually into smaller grains, with no chemical change.
What is chemical weathering
Decomposition of rocks, eg the separating of the minerals found in the rock.
What is salt crystal growth
Occurs when saline solutions enter the rock pores or cracks and evaporate which leaves behind salt crystals. When this happens repeatedly, the salt builds up and the crystal expands. As they expand, they exert pressure on the rocks which eventually causes the rock to disintegrate.
What is Carbonation
The process by which rocks that contain calcium carbonate are broken down. Co2 dissolves into rainwater to produce a weak carbonic acid rain which reacts with the calcium carbonate causing the formation of calcium bicarbonate. This dissolves in water.
What is oxidation
Rusting, whereby the rock minerals lose one or more ions in the presence of oxygen, when they oxidise they break down.
What is Chelation
Organic acids are released when organic matter decomposes, these acids cause the removal of metallic cations from minerals in rocks, causing them to break down.
What is frost wedging
Occurs when water enters cracks in the rocks, when it freezes it expands by 9% which forces the cracks to widen, eventually rock shatters.
What is mass movement
The downslope movement of regolith ( weathered material) under the influence of gravity
What is the shear strength
Forces holding a slope in place
What is shear stress
Forces drawing materials downslope eg gravity or mass
Causes of mass movement
Removal of vegetation- Less interception so more water in soil, heavier mass, so increased shear stress. Less friction so less sheer strength.
Weathering- Breakdown of rock, changing the binding, reducing cohesion between particles, so sheer strength decreases.
What is rockfall
Material breaks up and falls in pieces usually associated with nearly vertical slopes. Only more resistant rock can sustain these angles
What is slumping
Downward movement of unconsolidated rock debris that’s usually caused by the removal of the earth at the foot of a slope.
What is soil creep
1-2cm per year, occurring on very gentle slopes. soil particles repeatedly expand and contract in wet and dry periods. When wet, soil particles increase in size and weight, and expand at right angles to the slope. When the soil dries out, it contracts vertically and is drawn downslope.
What is rock type
Refers to the characteristics of the rocks in particular the resistance and permeability.
What is presentation
How the rocks present themselves to the coast, concordant or discordant
Factors affecting marine erosion
-Sub-aerial processes, e.g weathering.
-Wind fetch
-Geology of rock
-Beach pressure and character.
What is abrasion
Abrasion is when rocks and other materials carried by the sea are picked up and hurled by strong waves against the coastline, causing material to be broken off and carried away by the sea.
What is hydraulic action
The sheer force of water crashing against the coastline, causing material to be dislodged and carried away by the sea.
What is cavitation
Air bubbles trapped in the water get compressed into small spaces like cracks in the cliff. These bubbles implode as waves break, creating a small shockwave that weakens the rock.
What is attrition
Individual sediment particles collide with each other
What is wave quarrying
When high energy, tall waves hit cliff with power to enlarge joints and remove sediment.
