Geomorphological processes Flashcards
What is the main acting agent that leads to cliff collapse?
Weathering
What are the three types of weathering?
- Chemical
- Physical
- Biological
Define weathering
It’s the wearing away of rocks in situ.
Define chemical weathering
Both rain and seawater contain chemicals that can react with chemical compounds in the rock, altering its structure.
Define physical weathering
Internal pressures are exerted on rock as a result of changes in the physical structure within its mass.
Define biological weathering
Living organisms can contribute to the weathering of coastal rocks through the activity of plants and animals.
What are the 6 types of erosion?
Hydraulic action, quarrying, cavitation, abrasion, solution, and attrition
Define hydraulic action
Waves break against a cliff face and water forces itself into cracks - compressing the air inside.
Define quarrying
Destructive waves in storm conditions plunge heavy hydraulic pressure on cliff faces. The vibration of the cliff can dislodge bits of rock and undercuts the base of the cliff.
Define cavitation
The opening up of cavities within cliffs due to changes in pressure as waves crash into and out of cracks in the rock.
Define abrasion
The launching of rock fragments and pebbles against cliffs by waves can break off pieces of solid cliff and weaken rock structure.
Define solution
Chalk and limestone is dissolved and rock is removed in solution.
Define attrition
The smoothing and reducing of angular rock fragments into pebbles, shingle, and eventually sand particles.
Define mass movement
The movement of consolidated material (solid rock) and unconsolidated material (clay and soil) due to gravity.
What 5 factors affect mass movement?
- Rainfall
- Rock type
- Human activity
- Vegetation cover
- Angle of the slope
What is cliff slumping?
The rapid movement of a mass of earth or rock sliding along a concave surface.
Describe the 3 stages of cliff slumping
Stage 1 - the soft boulder clay holds rainwater
Stage 2 - waves erode the base of the cliff creating a wave cut notch. The clay becomes saturated and forms a slip plane
Stage 3 - the weight of the saturated cliff causes it to slump
Define traction
Large particles like boulders are pushed along the sea bed by the force of the water
Define suspension
Small particles like silt and clay are carried along in the water
Define saltation
Pebble sized particles are bounced along the sea bed by the force of the water
Define solution
Soluble materials dissolve in the water and are carried along
How does a mudslide occur?
When saturated soil and weak rock flows down a slope.
Typically occurs when cliffs are made up of boulder clay
What is a rockfall
Involves fragments of rock breaking away from the cliff face, often due to freeze-thaw weathering.
When does a landslide occur?
When waves break at the foot of a cliff - causing erosion. This creates a wave-cut notch and as this increases in size the weight of the cliff becomes too much to support - causing a landslide to occur.
