Coasts KQ2- formation of landforms Flashcards
Describe what a wave cut platform is
A flat, gently sloping horizontal areas of rock found at the base of cliffs
Describe what a cliff is
Near vertical faces of exposed rock, where the sea meets the land
Give an example of an area where cliffs and wave cut platforms are found
Broad bench, Kimmeridge, Dorset
Outline how wave cut platforms are formed
- waves erode the base of a cliff by abrasion, hydraulic action, pounding
- This leads to undercuttin and formation of a wave-cut notch
- Eventually unsupported rock collapses
- The collapsed cliff material is washed away by waves
- Cliffs retreat as this occurs repeatedly
Describe what a wave-cut notch is
A small indent at the base of a cliff
Describe what bays are
bodies of water which are surrounded by land on three sides
Define weathering
The in-situ disintegration of rock by chemical, biological, and physical processes
How does physical weathering allow other weathering to take place?
Physical weathering breals rock into smaller pieces, which increases the surface area for other weathering to take place
Give 4 examples of physical weathering
- Freeze-thaw weathering
- Pressure release
- Thermal expansion
- Salt crystalisation
Describe the process of freeze-thaw weathering
- water enters cracks and freezes
- when water freezes it expands
- expansion of water causes pressure on rocks
- this can split even resistant rock and cause pieces to break off
Describe the process of pressure release weathering
- Overlying rocks are removed by weathering and erosion releasing pressure on rock
- Underlying rock expands and fractures
- Causing parallel fractures to form
Describe the process of thermal expansion weathering
- Rocks experience repeated cycles of temperature change
- When rock is heated it expands, and when it is cooled it contracts
- This causes the outer layers of rock to crack and flake off
Describe the process of salt crystallisation
- Salts precipitate and form crystals in pore spaces in rocks
- This causes pressure within the rock
- Causing rock to disintegrate
Which salts are particuarly effective at salt crystallisation weathering?
Sodium sulfate and sodium carbonate
What is chemical weathering?
Weathering which involves reactions between moisture and some minerals within the rock
Name 5 examples of chemical weathering
- Oxidation
- Carbonation
- Solution
- Hydrolysis
- Hydration
Describe the process of oxidation weathering
- Minerals in rock react with oxygen from air or water
- The original structure of the rock is destroyed and disintegrated
Which type of rock is particularly susceptible to oxidation?
Sandstone- as it contains a high % of Iron
Describe the process of carbonation
- Rainwater reacts with dissolved carbon dioxide to produce weak carbonic acid
- The carbonic acid reacts with calcium carbonate to produce calcium bicarbonate
- Calcium bicarbonate is soluble in water
- Rocks containing calcium carbonate are dissolved
Describe the process of solution (as a weathering process)
- Some salts are soluble in water or in specific conditions
- Rock minerals dissolve, reducing the size of rocks
- The structural integrity of the rock can be undermined
Describe the process of hydrolysis (weathering)
- Silicates combine with water, reacting chemically to produce clays
- The secondary minerals that are produced are much softer than the original rock
- The rock can be eroded more easily
Describe the process of hydration (weathering)
- When water reacts with rocks new minerals are created
- The new minerals have a larger volume than the original rocks
- This causes pressure to be exerted
- Surface flaking of rock occurs
What is biological weathering?
Weathering which may consist of physical or chemical processes but these are crucially as a result of the action of living organisms
Give 2 examples of biological weathering
- Tree root weathering
- Organic acids/chelation
Describe the process of tree root weathering
- Tree roots grow into cracks and exert pressure
- If these trees topple they act as a lever
- Pressure exerted on cracks can expand fissures in the rock
- Trees toppling bring soils and rock to the surface allowing them to be weathered further
Describe the process of chelation (weathering)
- Molluscs secrete acids
- Decomposition of plant and animal litter can cause soil water to become acidic
- Acidic soil reacts with some minerals
- Molluscs cause small surface hollows in rock
Define mass movement
The downslope transportation of material under gravity
What are the factors that affect mass movement?
- amount of water
- vegetation
- marine processes/wave action
What are the 3 categories that mass movements can be split into?
- Fast
- Slow
- Flow
Give an example of flow mass movement
Mudflow
Give 3 examples of fast mass movement
- Rock slide
- Rock fall
- Slumping
Give 2 examples of slow mass movement
- Soil creep
- Rain splash
Describe the process of soil creep
- Individual soil particles are pushed down or heaved to the surface by wetting, heating, or freezing
- Soil particles move at right angles to the surface
- When dry soil particles move under the influence of gravity
Describe the process of rain splash (mass movement)
When a raindrop falls on soil it dislodges soil particles
Describe the process of mudflow
- Material on a slope becomes saturated with water, making it much heavier
- Material moves down a slope in the form of a fluid
- Most likely to occur after intense rainfall
What geology makes a slope vulnerable to mudflow?
Thin soils overlying impermeable rock
Describe the process of rock slides
- Rocks have jointing or bedding planes roughly parallel to the angle of the slope
- Once weathered, large blocks of rock can slide downhill
Describe the process of rockfalls
- Occur on slopes in excess of 40°
- Can result from extreme physical or chemical weathering, storm action, or earthquakes
- Bits of rock fall off the cliff face
- Material that accumulates at the base is called tallus/scree
Describe the process of rotational slumping
- Saturated soil slumps down a curved surface
- Occur where weaker rocks/clays overlay more resistant or impermeable rock
- Creates curved slip planes
