Coasts Flashcards
Explain the 4 different types of erosion
Hydraulic action: strong waves crash into the cliff face. Trapped air is blasted into holes and cracks in the rock causing them to break apart
Corrasion/abrasion: rocks being thrown into the cliffs by waves and breaking off bits of the cliff
Attrition: rock fragments carried by the sea knock into each other, they break down and become smaller and more rounded
Solution: slight acidity of sea water causes bits of the cliff to dissolve
What is deposition?
When eroded material is stopped by constructive waves
What are destructive waves?
Fairly weak swash Strong backwash Erode and transport material away from beaches Steep beaches Breaks downwards with great force
What are constructive waves?
Flat and low Strong swash Weak backwash Deposit material and build beaches up Gentle beaches
What is coastal erosion?
The wearing away of the coast by destructive waves
How do waves form?
Transfer of energy
Friction that occurs when wind blows over water
When it reaches the shore, the lower part slows due to friction with the sea bed but the upper part continues to move. It topples and breaks against the cliff face.
What is the size and energy of a wave influenced by?
How long wind has been blowing
Strength of wind
How far the wave has travelled
What is transportation?
The movement of material in the sea and along the coast by waves
What are the 4 different types of transportation?
Traction: large material rolled along sea floor
Suspension: beach material is suspended and carried by waves
Saltation: beach material is bounced along sea floor
Solution: material is dissolved and carried by water
What is longshore drift?
The process of waves moving material along a coastline
How does longshore drift occur?
- Waves approach the coast at right angles
- The backwash is at right angles to the coast as this is the steepest gradient
- The material will move up the coast
How is a stump formed?
- Lines of weakness such as faults/cracks occur in headlands
- Abrasion and hydraulic action erode the fault to form a cave
- The cave is widened and deepened
- The sea cuts through to form an arch
- The sea erodes the foot of the arch and widens it
- The roof of the arch becomes too heavy and collapses
- Part of the former cliff is now isolated as a stack
- Over time, the stack is eroded and it might be undercut and collapse
- A stump is the remains of the eroded stack
How are cliffs formed?
When destructive waves attack the bottom of the rock face between the high and low water marks
How are wave cut platforms formed?
- Waves break against the cliff and erosion at high tide form a wave-cut notch
- The notch gets deepened until the overlaying cliff collapses
- A new wave cut notch is created and the sequence continues
- The cliff line gradually retreats leaving a gently sloping wave cute platform. This is the gently sloping rocky area between the high and low water marks
What is a spit and how is it formed?
A spit is a ridge of sand and shingle projecting from the mainland into the sea
- Longshore drift deposits materials at an angle of about 45 degrees
- The backwash, however is at right angles
- The materials therefore move in a zig-zag fashion
- There is deposition of material at the change of direction of the coast, which leads to the formation of a spit
- Curving at the end may be caused by a change in wind direction
What is a bar and how is it formed?
A bar is a ridge of sand and shingle which joins two headlands, cutting off a bay
- A spit continues to grow as more material is deposited
- Sometimes, the spit will eventually join two headlands forming a bar
- The bay is cut off and a lagoon is formed
What is a tombolo and how is it formed?
A tombolo is a ridge of sand and shingle joining the mainland to the land
Sometimes a spit will grow out from a headland and will eventually join the mainland
How are bay and headline coastlines formed?
- Where rocks of different hardness and resistance meet the sea, the weaker rocks are eroded back more quickly to form bays
- In the shelter of a bay, constructive waves deposit material from elsewhere and beaches are formed
- The stronger rocks resist wave attacks for longer and stand out as prominent rocky headlands.
What is the difference between a concordant and discordant coastline?
Concordant coastlines are where bands of hard and soft rock run parallel to the coastline while discordant coastlines are where bands of hard and soft rock run perpendicular to the coastline
What are sand dunes?
Small ridges/hills of sand found at the top of a beach above the usual maximum reach of the waves
How are sand dunes formed?
- Sand dries out
- Wind picks up particles of sands from beaches, especially at low tide
- The sand is deposited around an obstruction
- The dunes build up over time from an embryo dune to an established dune
What are the conditions needed for sand dunes to form?
A supply of dry sand over a wide beach
An area of low lying sand behind the beach
Predominantly onshore winds
What are coral reefs?
A coral reef is a line of coral polyp found in warm, shallow seas. They are formed when polyps build limestone around themselves and then these foundations are used by other polyps. When the limestone foundations build up, they are called coral reefs.
What are the conditions needed for coral reefs?
Minimum water temperature of 18 degrees (warm waters) Light conditions Water depth of less than 25m Salty water-no less than 30-32psu Clean, clear water
Where are mangrove swamps formed?
On the coastline in an intertidal zone
What conditions can mangroves endure?
Flooding of saltwater by the sea Flooding of freshwater by rainfall Alternating salt and temperature levels Choking mud They have special adaptations to help them survive
Opportunities presented by coasts
Areas of beautiful scenery/good views/enjoy the scenery;
Use by tourists/for leisure activities or example/income from tourism;
Hiking/coastal paths;
Fishing industry;
Development of harbours/ports;
People live there/residential/retirement.
Hazards presented by coasts
Tropical storms Flooding High winds Hurricanes Landslides Tsunamis Storm surges
