Coasts part 3

• What is coastal deposition

  -Coastal deposition describes when material is dropped by seawater on the shore.

  -Coasts get built up when there is more deposition than erosion.
• What are the erosional landforms

  wave cut platform

  headlands and bays

  caves

  cracks

  stacks

  stumps
• Explain the process of the wave cut platform

  -waves through hydraulic action cause erosion at the foot of the cliff

  -this erosion of a cliff at the base forms a wave cut notch

  -as this grows the rock above it becomes unstable and eventually collapses

  -the collapsed material is washed away and a new notch starts to form

  -repeated collapsing causes the cliff to retreat

  -a wave cut platform is left behind as the cliff retreats
• Describe a headland


  a headland is a cliff that sticks out to sea which is surrounded by sides of water. They form from hard rock e.g. limestone and chalk which are harder to erode

  
• Describe a bay


  a bay forms from soft rock and forms between headlands e.g. clay and sand which is easier to erode due to hydraulic action

  
• How do cracks appear in a cliff

  Cracks appear in the headland when the force of the waves (hydraulic action) crashes into them
• How doe caves form from cracks

  Caves will occur when waves force their way into the cracks in the cliff making them bigger
• How does an arch form from a cave

  Eventually when the cave breaks through due to hydraulic action and abrasion an arch will form

  
• How does a stack form from a arch

  the arch becomes wider due to erosion at the base until it can't support the top of the arch. When the arch collapses it leaves the headland on one side and a stack (a tall column of rock)on the other
• How does a stump form from a stack

  the stack will be attacked at the base in the same way that a wave-cut notch is formed (abrasion and hydraulic action). This weakens the structure and will eventually collapse to form a stump
• How is a coast built

  a coast is built up when the amount of deposition is greater than the amount of erosion
• What are the factors affecting the amount of deposition

  lots of erosion-lots of material available

  lots of transportation- lots of material brought into an area of the coast

  low energy waves- strong swash and weak backwash so material is deposited not eroded
• What are the five depositional landforms

  -spits

  -bars

  -beaches

  -tombolos

  -sand dunes
• Describe the formation of a beach

  Destructive waves erode cliff material. This material is transported by longshore drift. Constructive waves deposit material when they break in a sheltered bay, this forms a beach. A sheltered area like a bay is required so the beach builds up. Not all beaches are made of sand . For example much of the south coast of England has pebble beaches
• Describe the formation of spits

  A spit is a long narrow ridge of shingle (material) and sand which stretches out from the coast

  sediment that destructive waves have eroded from the cliff is carried by longshore drift in the direction of the prevailing wind. When there is a change in the shape of the coastline/cliff deposition occurs close to the shore. A long thin ridge of material is deposited. This is the spit. A hooked end is made if there is a change in wind direction. Waves cannot get past a spit therefore the water behind a spit is very sheltered
• Describe the formation of a bar

  a bar is formed when the spit extends out to sea and joins together two headlands. This allows a lagoon to form behind the bar as its protected from the waves of the sea
• Describe the formation of tombolos

  A tombolo is formed when the spit extends out to sea from the mainland and joins itself to an island. Overtime the deposition can be so great that it is possible to walk along the tombolo to the connecting island
• Describe the formation of sand dunes

  sand deposited on the beach has been blown inland by onshore winds to form dunes. Dunes change in form and appearance, the further inland. Embryo dunes form around deposited obstacles, they have no to little vegetation. As you move further inland the dunes become stabilised by vegetation to form yellow dunes and mature dunes
• What is the case study for coastal landforms


  Swanage
• Where is Swanage


  Swanage is a seaside town in Dorset on the south coast of England. It is located in a sheltered bay and has a broad, sandy beach. I
• What is the geology of Swanage

  -The rocks have been folded and tilted so that bands of different rock types reach the coast

  -the indented coastline of headland and bays is a discordant coastline. On the south coast there is only one rock type forming a relatively straight section of coast called a concordant coastline.

  -To the north of Swanage is Poole Harbour- one of the UK's largest natural harbours. Deposition has taken place here in the sheltered bay

  -Two spits have formed at the mouth of the harbour on the north and south sides

  -At Studland there are lagoons, salt marshes and sand dunes

  -There are chalk headlands at Ballard point to the north of Swanage Bay. There are also impressive white chalk cliffs and many isolated stacks , including an isolated stack known as 'Old Harry