glaciation coasts Flashcards
(14 cards)
hydraulic action
caused by waves smashing against cliffs. the waves force air into cracks in rocks causing pressure to build.
when the wave retreats the air expands,as this repeats the rock begins to fall off
wave pounding
waves crash onto cliffs, their impact breaks down the rock
abraision
the wearing away of coastal rock by rock debris hurled against the coast by waves
solution/corrosion
when salt and weak acids in the sea dissolve cliff rocks
attrition
when waves cause rocks to bang into each other and break up
biological weathering
plant seeds get into cracks in rocks and begin growing as they grow their roots exert pressure on the rocks causing them to fracture
chemical weathering
hydrolysis involves chemicals in water dissolving rocks
oxidation- salt crystals can penetrate the cliff face where there are rocks containing iron oxidation can the occur causing it to break the rock down creating a rust effect
freeze thaw weathering
headlands & bays
+formation of a headland
+example
headland- peice of coast that sticks out into the sea
bay- sheltered peice of land that has a headland either side
headland form along discordant coastlines in which bands of soft and hard rock outcrop at right angles to the coastline,
due to the presence of soft and hard rock differential erosion occurs with the soft less resistant rock eroding quicker than the hard resistant rock, where the erosion of the soft rock is rapid bays form, where there is more resistant rock erosion is slower and the hard rock is left sticking out into the sea as a headland (eg.swanage bay)
formation of cave, arch, stack, stump
once a headland has formed it is then exposed to the force of destructive waves and begins to erode.
-first the sea attacks the foot of the cliff and begins to erode areas of weakness such as joints and cracks though hydraulic action, abraision, attrition, solution, gradually cracks get larger developing into small caves
-often another cave will form on the other side of the headland. further erosion widens the caves and where the fault lines run through the headland, the two caves will eventually erode into the back of eachother forming an arch passing through the headland (eg. durdle door)
-erosion such as hydraulic action at the base of an arch aswell as biological and chemical weathering of the roof of the arch weakens the structure until it collapses leaving a stack. a stack is a column of rock standing separate from the headland (eg. old harry)
-the stack is continuously acted on by wave based processes at the base and sub-areal processes above will eventually collapse forming a stump which will be covered by water at high tide (eg. old harrys wife)
formation of wave cut platforms
cliffs are steep rock faces along concordant coastlines with resistant rock parallel to the coast.
- the waves attack the base through (abraision, hydraulic action, attrition, solution)
-the erosion is greatest at its base where large waves break. here hydraulic action undercuts the foot of the cliff forming an indent called a wavecut notch.
-the cliff is also effected by corrosion and abraision
-undercutting continues, eventually the overhanging cliff collapses downwards, this process continues and the cliff gradually retreats and becomes steeper.
-as the cliff retreats a gently sloping rocky platform is left at the base. (wavecut platform) eg. kimmeridge bay, dorset
formation of a spit
sand spits are formed by the process of longshore drift. swash is where waves driven by prevailing wind push material up the beach at an angle, the returning backwash is dragged back by gravity down the beach at right angles, spits form when there is a change in direction on the coastline allowing a sheltered area for deposition. material slowly builds up to appear above the water, the spit develops as long as the supply of deposites is greater than the amount of erosion. the shape can become hooked or curved at the end by changes in wind direction.
eg. blakeney point
formation of a sandbar
longshore drift which is the movement of sediment along a coastline due to prevailing winds causing the angled approach of waves. allows the build up of transported material. if a sand spit occurs near a bay then the spit can continue to form across the mouth of the bay completed , blocking it off. (eg. oxford ness)
formation of a tombolo
-formed where a spit continues to grow outwards joining land to an offshore island.
-formed when waves near an island are slowed by the shallow water surrounding. these waves then bend around the island to the opposite side of the island. the waves sweep sediment together from both sides. eventually when enough sediment builds up the shoreline known as a spit will connect with an island and form a tombolo (eg. holy island)
