Erosion and weathering Flashcards
what is hydraulic action?
Air bubbles are forced into cracks in the cliff as the waves crash into them. This creates enormous pressure at this point. As the waves retreat the pressure is released. Overtime this weakens the cliff face and huge chunks of cliff can break off
What is corrasion?
loose rocks are thrown against the cliff by waves. This wears the cliff away and chips bits of rock off
what is corrosion?
sea water forms a weak carbonic acid when it absorbs carbon from the air. This dissolves rock such as limestone because they contain calcium carbonate. the cooler the water the more carbon will be absorbed thus more carbonation
what is attrition?
loose sediment knocked off the cliff by hydraulic actionand abrasion is swirled around by the waves. It constantly collides with other sediment and gradually gets worn down into smaller and rounder sediment
what are the factors which influence erosion?
- Hard rocks (Basalt, Granite) will erode slowly producing high steep cliffs
- Soft rocks (clay) are eroded more quickly and are likely to be affected by mass movement therefore creating less steep cliffs
- Joints in rocks allow for greater erosion because they increase surface area for the rocks to be attacked
- The lithology of the rock eg. Concordant or discordant
what does concordant mean?
when bands of rock lie parallel to the coast
what does discordant mean?
when bands of rock lie at right angles to the coast
which type of coast has more feature?
Discordant coastlines
what are the other factors which can affect erosion?
- Wind (larger fetch = more wave energy= increased erosion rates
- Waves - destructive waves= greater erosion rates
- sediment supply= more corrasion and attrition
what is freezethaw?
during the day water from the waves seeps into the joints of the rock and settles. At night the temperature drops and the water freezes in the crack, expanding by 9%. this exerts pressure on the joints, enlarging them over time. once the process has been repeated the rock will weaken and begin to disintegrate.
what is salt crystal weathering
This happens when salt water soaks into the pores of the rock. When evaporation occurs, salt crystals are left behind in the cracks. these grow in size and exert pressure on the rock joints. this process is repeated until the rock disintegrates
what is biological weathering?
- Plant roots can grow along bedding planes and joints, widening them until blocks of rock become detached
- This type of weathering can also increase chemical weathering by releasing humic acids which encourages hydrolysis
- animals can also burrow into the rock which causes disintegration
what is carbonation?
carbon dioxide dissolves into rainwater and forms a weak carbonic acid. this can attack rocks such as lime stone which contains calcium carbonate causing them to dissolve into calcium bicarbonate.
What are the two most common types of mass movement?
rock fall and rotational slump
what factors influence which type of mass movement will occur?
- Weighting of the land
- the cohesion of the soil and rock
- how jointed the rock is
- traffic vibrations from nearby major roads
- hard or soft rock
