Coasts Flashcards
Mechanical weathering
breakdown of rock without changing its chemical composition
Salt weathering
main type of weathering that affects coasts
1) sea water gets into cracks in the rock
2) when the water evaporates - salt crystals form
as the crystals form they expand - puts pressure on the rocks
2) repeated evaporation of saltwater and the forming of salt crystals widens cracks and causes rock to break up
Chemical weathering
breakdown of rock by changing its chemical composition
Carbonation weathering
type of chemical weathering that happens in warm and wet conditions
1) seawater and rainwater have carbon dioxide dissolved in them - makes them weak carbonic acids
2) carbonic acid reacts with rock that contains calcium carbonate such as Carboniferous limestone - so rocks are dissolved by rainwater
Biological weathering
breakdown of rocks by living things
plant roots break down rocks by growing into cracks on their surface and pushing them apart
Mass movement
shifting of rocks and loose material down a slope e.g. a cliff
happens when the force of gravity acting on a slope is greater than the force supporting it
causes coasts to retreat rapidly
more likely to happen when the material is full of water - acts as lubricant and makes material heavier
3 processes of erosion
Hydraulic power
Abrasion
Attrition
Hydraulic power
waves crash against rock and compress the air in the cracks
this puts pressure on the rocks
repeated compression widens the cracks and makes rock break off
Abrasion
eroded particles in the water scrape and rub against rock - removing small pieces
Attrition
eroded particles in the water smash into each other and break into smaller fragments
their edges also get rounded off as they rub together
More resistant rocks
Hard rocks like limestone and chalk are more resistant
takes longer for them to be eroded and weathered by physical processes
Less resistant rocks
Softer rocks like clay and sandstone are less resistant
eroded and weathered more quickly
Joints and faults
cracks and weaknesses in the rock
rocks with lots of joints and faults erode faster
Discordant coastlines
coastlines made up of alternating bands of hard and soft rock that are at a right angle to the coast
Concordant coastlines
coastlines that are made up of alternating bands of hard and soft rock that are parallel to the coast
erosional land forms like bays and headlands are more common on…
Discordant coastlines
because bands of rock are being eroded at different rates
Fewer erosional land forms occur on…
Concordant coastlines
because they are eroded at the same rate along the coast
What increases the rate of salt weathering?
Warmer temperatures - water evaporates more quickly
Impact of storms on UK coastlines
Storms are very frequent in many parts of the UK especially in winter
strong winds create high energy destructive waves which increase erosion of the cliffs
intense rainfall can cause cliffs to become saturated - makes mass movement more likely
What are the prevailing winds in the UK?
Warm south westerlies - bring storm from the Atlantic Ocean
south coast is exposed to these
Destructive waves
1) waves that carry out erosional processes
2) high, steep, have high frequency (10-14 waves per minute)
3) backwash is more powerful than swash - so material is removed from the coast
4) storms increase the erosional power of destructive waves - can lead to increased rates of coastal retreat
Backwash
the movement of the water back down the beach