Coastal processes Flashcards
weathering
this is the breakdown of the rock situ (ie the stone doesn’t move)
what are the different types of weathering?
-chemical
-mechanical
chemical weathering
caused by a chemical reaction when rainwater hits rock and decomposes it
what are the different types of chemical weathering?
-carbonation
-hydrolysis
-oxidation
carbonation
when carbonic acid in rain water reacts with calcium carbonate in limestone to form calcium bicarbonate, this is soluble, so limestone is carried away in solution
hydrolysis
when acidic rainwater breaks down the rock, causing it to rot
oxidation
when rocks are broken down by oxygen and water
mechanical weathering
results in rocks being disintegrated rather than decomposed, it is usually associated with extremes of temperature
what are the different types of mechanical weathering?
-freeze thaw weathering
-salt wathering
freeze thaw weathering
Happens when water enters cracks in rock. When the night temp falls below freezing, this water freezes and increases in volume by nine percent, putting pressure on the rock around the crack. If daytime temp rises above freezing, the ice will thaw and relieve the pressure. Constant repetition of this daily freezing and thawing cycle causes angular rock fragments to break away and collect at scree at the base of the cliff.
salt weathering
when salt spray from the sea gets into a crack in a rock, it may evaporate and crystalise, putting pressure on the surrounding rock and weathering the structure
mass movement
is a result of different coastal processes
what are the different types of mass movement?
-sliding
-slumping
-rock falls
sliding
large clumps of rock slide down the slope quickly without warning
slumping
the clay becomes saturated during heavy rainfall and oozes down towards the sea as part of a mud or debris flow
where is slumping most common?
where cliffs are made of clay
rock falls
well joined rock faces are prone to freeze thaw weathering, which results in falling rocks losing contact with the rock face, at the bottom of the cliff they can fan out to form scree slopes
what are the different processes of erosion?
-hydraulic action
-abrasion
-attrition
-solution
hydraulic action
water crashes against cliffs and the air and water is compressed into the cracks, when the sea moves away again the air expands, explosively weakening the rocks, enlarging the cracks and breaking pieces off
abrasion
very effective as it’s caused by broken rock fragments battering the land and breaking off other pieces of rock
attrition
occurs when rock fragments collide and get worn down into smoother and smaller pebble
solution
involves chemical action of sea on rock, if the rock is limestone, it dissolves in the sea water, some sea salts can also react with certain rocks and cause them to disintegrate
what is longshore drift?
-longshore drift happens when waves break down at an oblique angle to the shore due to prevailing winds
-this means that each wave pushes material along the beach a bit more
-many depositional features such as spits are formed by this process
what is transport along the coast?
when waves move material across a beach
what are the different types of transportation?
-suspension
-solution
-traction
-saltation
-deposition
suspension
fine sediment is carried as a suspension in the water, making it look muddy or murky
solution
dissolved material is carried along in solution so you can’t see it
traction
larger pebbles are rolled along the sea bed
saltation
small pebbles are moved when one pebble hits another, causing it it bounce, this bouncing can set up a chain reaction
deposition
this is the dumping of eroded material on the land by constructive waves, it happens when waves have less energy, it creates a variety of landforms
