Coastal Features Flashcards
Explain the formation of a sand spit
Low edges of sand/shingle slowly extend from the shore across a bay or a river estuary and are caused by longshore drift
Waves are driven by the prevailing wind, pushing material back up the beach known as the swash
Returning backwash is dragged back by gravity down the beach at right angles
Material builds up and appears above the water, begins to grow longer and wider
Spit develops as long as the deposits are greater than erosion
Stacks, stumps and caves
Waves attack lines of weakness
Hydraulic action and abrasion widen these faults into cracks
Cave is formed - becomes an arch
This is accessible to the sea on both sides
Stacks, stumps and caves contributions
Freeze Thaw weathering weaken the rock surrounding a cave or arch - making it more susceptible to movement and collapse
Cove formation
Band of resistant rock - Outside
Less resistant rock - Inland
Waves seek out faults in the hard rock and erosion through abrasion and hydraulic action occurs through to the soft rock behind
Waves erode the soft rock faster leaving a circular cove with a narrow entrance where the sea enters.
Waves get refracted here and spread out to erode in all directions
Formation of bays and headlands
Sea erodes bands of rock at different rates - differential erosion
Hydraulic action, abrasion and corrosion are more effective at eroding softer rock particularly during storms - eroding further inland than the harder rock
Calmer weather means that the hard rock absorbs a lot of the wave energy - refracting the waves into the area with the softer rock, allowing sediment to be deposited and accumulate as beaches
Hard rock is left jutting out as a headland - softer rock gets eroded into carved sand filled bays
Cliffs and cliff retreat
Soft rock erodes easily to create gently sloping cliffs
Hard rock erodes slowly to create steep cliffs
Weather weakens top of the cliff
Sea attacks cliff base to form a wave-cut notch
Cliff continues to retreat as this repeats
Tombolos
Longshore Drift
Formed where a spit continues to grow until it reaches an island, forming a link with the mainland, just like bridges
Bar
Ridge of sand and shingle which has joined two headlands, cutting off a bay
Spit grows the whole way across a bay
Offshore sandbank develops and is moved towards the coastline by waves and wind until it joins the mainland
Lagoon created behind this may be filled as a salt marsh - over time is filled with deposits
Longshore Drift
Material is moved up the beach at an angle by the swash
Waves approach the beach at an angle controlled by prevailing wind
Material carried directly down the beach in the backwash under gravity
