constructive waves
- 6-9 waves per minute
- calm weather
- less powerful
- deposit material
- long wavelength, low in height
hydraulic action
- sheer weight and impact of the water against the coastline
- pockets of air widen cracks
- put under high pressure by the water
abrasion
particles carried by the water crash against the cliff
attrition
- particles carried by the waves are reduced in size as they collide with eachother and the rock face
- pebbles are broken down into sand sized articles
solution
- when salts and other acids in the sea water dissolve certain rock types e.g limestone
cliff retreat
- erosion focused between high tide marks creating a wave cut notch
- an overhang is created
- overhang grows until it collapses causing the cliff to retreat
- process repeats
wave cut platform is left behind
headlands and bays
headlands are formed when the sea attacks a section of coast with alternating bands of hard and soft rock
the rocks erode and different rates leaving a section of land jolting out into the sea
the areas where soft rock has eroded away next to a headland are called bays
factors that affect the rate of erosion
type of rock:
- hard rock erodes slower than soft rock
characteristics of rock:
- cliffs with joints, faults or bedding planes erode quicker because there are more places for the waves to exploite
arrangement of rock
weather:
- storm conditions are when the highest rates of erosion are recorded
longshore drift
- particle is carried up he beach by the swash roughly in line with the prevailing wind
- gravity brings particle back down
formation of spits
- when sediment starts to build up away from the coastline because the land changes direction
- fast flowing river stops the spit from going across to the other side of the bank because the river washes away the material
- a salt marsh is formed behind the spit
bedding planes
- horizontal beds
- differing rate of erosion
- vertical beds
- uniform resistance to erosion
- sloping beds
- sea ward dipping of bedding planes loose material can slide easily towards the sea
bars
if a spit joins one part of the mainland to another it is called a bar
lagoon is formed behind the bar
tombolo- when a spit joins an offshore island
destructive waves
- 11- 15 waves per minute
- erode coast
- winter
- created in storm conditions
- short wavelength, steep
- stronger backwash than swash
eustatic sea level change
- world wide sea level change that is caused by melting ice caps and glaciers
isostatic sea level change
- local or regional relative change in sea level, which is caused by a change in the level of the land
- this may be caused by the land being jolted upwards by tectonic forces or by land that was compressed beneath ice sheets over a mile thick 18,000 years ago rebounding upwards and the pressure is lifted.
esturies
- drowned valley
- rising sea levels from glacial ice melt, flood the broad, flat flood plains of rivers, creating wide shallow, salt water, tidal river mouths
Fjords
- drowned glacial valleys
- steep, narrow, rock walled sides
- very deep
- carved out by glaciers- found in the west of norway
Ria
- this is a drowned unglaciated river valley
- dendritic in shape
- large mouth for a small river e.g. milford haven
raised beach
- falling sea level leaves the old beach raised above the new, present day shoreline
- this may have an old cliff line behind the beach, this is called a relic cliff
