coastal processes Flashcards
rock is broken down by…
mechanical and chemical weathering
mechanical weathering (freeze thaw)
breakdown of rock without changing its chemical composition
e.g. freeze thaw weathering. water enters rock that has cracks, freezes, expands, putting pressure on the rock, when water thaws in contracts releasing pressure, repeated freez thaw causes large cracks and causes rock to break up
chemical weathering
breakdown of rock by changing its chemical composition
e.g. carbonation in warm and wet conditions. rainwater is a weak carbonic acid, this carbonic acid reacts with rocks containing calcium carbonate so the rocks dissilve to rainwater e.g. carboniferous limestone
mass movement
when a material falls down a slope - shifting of rocks and loose material down a slope when the force of gravity is larger than the force that is holding it. causing rocks to retreat rapidly. more likely to happen if the material if full of water as this makes it heavier. can create a scarp
constructive waves
deposit material - low freq - low and long - swash is more powerful than backwash so mat is deposited
destructive waves
erode the coast - high frequency, high and steep, backwash is more powerful than swash so material is moved
fetch and storm surges
a fetch is the distance the wind blows over the sea - larger the fetch the more powerful the wave
storm surges created by storms and temporary sea level rises caused as strong winds push water onshore
which 3 processes of erosion erode the coast
hydraulic power - waves crash against rock and compress the air in the cracks, putting pressure on the rocks, repeated compression widens the cracks and breaks bits of the rock off
abrasion - eroded particles in the water scrape and rub against rock removing small pieces
attrition - eroded particles in the water collide, break into smaller pieces and become more rounded
acronym for waves
contructive create beaches destructive destroy
longshore drift
waves follow the direction of prevailing wind, hitting the coast at an oblique angle, swash carries material up the beach in the same direction as the waves, backwash then carries material down at right angles towards the sea, over time material zig zags along the coast
what are the 4 other transportation processes
traction - large particles like boulders are pushed along the sea bed by the force of water
saltation - pebble sized particles are bounced along the sea bed by the force of water
suspension - small particles like silt + clay are carried along the water
solution - soluble materials like limestone dissolve in the water and are carried along
solution
solution - soluble materials like limestone dissolve in the water and are carried along
suspension
suspension - small particles like silt + clay are carried along the water
saltation
saltation - pebble sized particles are bounced along the sea bed by the force of water
traction
traction - large particles like boulders are pushed along the sea bed by the force of water
deposition
- occurs when water carrying sediment slows down and loses energy
- coasts build up when the amount of deposition is greater than the amount of erosion
- the amount deposited is increased in an area of a coast when there is lots of erosion elsewhere so more material is available and lots of material is transported into the area
constructive waves drop more material than they remove, more depo than ero
