Coasts Flashcards
mass movement
the movement of material down a slope due to gravity
sliding
large volumes of material moves downhill very rapidly, in a straight line, along a joint in the rock
slumping
saturated soil or rock, collapses in a rotational movement, down a curved slope
factors that affect mass movement
Slope angle
Vegetation cover
Water content
Rock type
Human activity
Climate
types of erosion
abrasion
hydraulic action
attrition
solution
hydraulic action
the sheer power of the waves as they smash against the cliff. air becomes trapped in the cracks in the rock and causes the rock to break apart from the pressure.
attrition
rocks in the water knock against each other. they break apart to become smaller and rounder
abrasion
pebbles grind along a rock platform, like sandpaper. over time, the rock becomes smooth
solution (erosion)
sea water dissolves certain types of rocks and breaks down some rock. in the UK, chalk and limestone cliffs are prone to this.
how are headlands and bays formed on a discordant coastline?
On a discordant coastline, Alternating bands of hard and soft rocks run perpendicular to oncoming waves The soft rock (e.g. clay) is eroded backward, forming an inlet As the inlet continues to erode it curves inward, and a bay is formed, usually with a beach The hard rock (e.g. limestone) is left protruding out to sea as a headland.
concordant coastline
coastline with bands of more and less resistant rocks that run parallel to the coastline e.g. Lulworth Cove
discordant coastline
coastline with bands of more and less resistant rock running perpendicular to the coastline. headlands and bays form here e.g. Swanage Bays
features formed on a discordant coastline
alternating bands of hard and soft rock form headlands and bays
how do concordant coastlines affect coastal landforms
how do discordant coastlines affect coastal landforms
deposition
a physical process where rocks and material are dropped by the waves that carry them
how does deposition work
when the sea loses energy, the waves drop the material it has been carrying. it can occur on coastlines that have
constructive waves
factors leading to deposition
waves starting to slow down and lose energy
shallow water
sheltered areas, eg bays
little or no wind
spit
a ridge of sand or shingle deposited by the sea. it’s attached to the land at one end, the other extended into the sea
bar
a ridge of sand or shingle deposited by the sea, across the entrance of a bay or river mouth
tombolo
a spit connecting an island to the mainland
bay
an area of sea, curved in shape which has been eroded between two headlands
saltmarsh
coastal wetlands that are flooded and drained by salt water brought in by the tides
headland
a steep sided cliff area of more resistant rock jutting out into the sea
lagoon
a shallow body of water protected from a larger body of water (usually the ocean) by (often) sandbars
wave cut platform
a flat area of rock at the base of a cliff seen at a low tide, where the cliff used to be
wave cut notch
a small indentation at the base of a cliff formed where wave action is greatest
cave
a hollow at the base of a cliff which has been eroded by the waves
arch
a rock bridge formed when the sea erodes a hole all the way through a headland
stack
an isolated column of rock, found at the end of a headland
stump
a short piece of rock found at the end of a headland formed after a stack has collapsed
formation of a stack/stump
- cracks and faults are widened in the headland through the erosional processes of hydraulic action and abrasion.
- As the waves continue to grind away at the crack, it begins to open up to form a cave.
3.The cave becomes larger and eventually breaks through the headland to form an arch.
4.The base of the arch continually becomes wider through further erosion,
until its roof becomes too heavy and collapses into the sea.
5.This leaves a stack (an isolated column of rock). - The stack is undercut at the base until it collapses to form a stump.
formation of a wave cut platform+notch
- the sea attacks the base of the cliff between the high and low water mark.
- a wave cut notch is formed by erosional processes such as abrasion and hydraulic action - this is a dent in the cliff usually at the level of high tide
- as the notch increases in size, the cliff becomes unstable and collapses, leading to the retreat of the cliff face
- the backwash carries away the eroded material, leaving a wave cut platform
- this process repeats and the cliff continues to retreat
formation of bar
- Sediment is carried by longshore drift.
- When there is a change in the shape of the coastline, deposition occurs.
- A long thin ridge of material is deposited. This is the spit.
- material is further deposited
- once it reaches the other headland the spit becomes a bar
- The area behind the newly formed bar is known as a lagoon.
formation of spit
- Sediment is carried by longshore drift.
- When there is a change in the shape of the coastline, deposition occurs.
- A long thin ridge of material is deposited. This is the spit.
- A hooked end can form if there is a change in wind direction.
- Waves cannot get past a spit, therefore the water behind a spit is very sheltered. Silts are deposited here to form a salt marsh.
formation of headlands and bays
Headlands and bays form along discordant coastlines. The less resistant rock (e.g. clay) is eroded quickly and this forms a bay. The more resistant rock (e.g. chalk) is eroded slower and sticks out into the sea, forming a headland.
berm
a ridge of shingle and sand that marks the normal high tide level on a beach
factors related to weather and climate that affect coastal erosion
Storm frequency
Prevailing winds
Seasonality
how does prevailing wind in the uk affect coastal erosion and retreat
Prevailing winds in the UK are from the south-west. This brings warm,
moist air from the Atlantic and frequent rainfall, which contributes to
weathering and mass movement on the coast.
how does seasonality in the uk affect coastal erosion and retreat
The four seasons have different impacts on coastal erosion. e.g. cold temperatures in winter
lead to freeze-thaw weathering in cliffs
how does stormy weather in the uk affect coastal erosion and retreat
- Coasts are often subject to strong winds, increasing the eroding power of the waves, and heavy rainfall contributes to mass movement
- Frequent storms can damage coastal landforms like spits. e.g. Spurn Head along the Holderness coast is at risk of being cut off from the mainland
- Beach sediment can be removed from a section of coastline.
- Sand dunes can be removed by storms.
