Erosion = the mechanical wearing away of rock with movement
● Remember: CASH
○ Corrasion
○ Attrition
○ Solution
○ Hydraulic action
Corrasion (abrasion):
● Destructive waves have enough energy to hurl
sand and rocks at the cliff
● Results in scratching/scraping of rock surface
● Can form a wave-cut notch
Attrition:
● Grinding down of load particles
● Pebbles collide with each other
● Jagged edges are worn away to make smooth
pebbles
● Some collisions may cause a pebble to smash
into several smaller pieces
Solution:
● Rock dissolve over time in water
○ eg/ limestone, chalk
Hydraulic action:
● Force of destructive waves pounding the base
of cliffs
● Causes repeated changes of air pressure →
compresses air
● Explosive effect as wave retreats and pressure
is released
● Material breaks off the cliff
Factors affecting rate of erosion:
● Fetch size
○ Large fetches = more destructive
waves
● Wind strength
○ Strong winds for a long time →
destructive waves
○ Common in winter
● Beach
○ Acts as a buffer between sea and cliffs
○ Waves lose energy
● Headland
○ Waves converge on a headland
○ Gain height and erosive energy
● Rock hardness
○ Soft boulder clay → 5 m a year eroded
○ Hard granite rocks → 0.001 m a year
eroded
● Rock joints
○ Water can force itself into a crack
○ Hydraulic action can occur easily
