Costal Environments Flashcards
Describe a constructive wave
Strong swash
Weak backwash
Describe a destructive wave
Weak swash
Strong backwash
Explain the erosional processes.
Hydraulic action - air in a rock crack, sea water crashes against it and forces rock to break apart as air has nowhere else to go
Abrasion - rocks rub together and scour the coast
Corrosion - sea water corrodes the rocks and slowly dissolve
Attrition - rocks bash together
Explain longshore drift
Eroded rock is picked up by waves and dragged along the coast.
Moves in direction of wind.
Backwash is at 90 degree angle to swash.
When run out of energy or coastline changes direction, sediment is deposited forming depositional landforms.
What are the three land processes?
Weathering - freeze-thaw, salt crystals, acid rain
Erosion - wind and rain
Mass movement - gravity, slumping and landslides
What is a concordant and discordant coastline?
Concordant - straighter coastline, outcrops run parallel to the sea, eroded to form wave cut notch, if hard rock is on edge, rock crashes down, if soft, rock slumps down
Discordant - rocks outcrop at right angles, eroded to form headlands (by crack, cave, arch etc) and bays - different strengths of rock on the coastline
How are caves, arches, stacks and stumps formed?
Erosion in a headland opens up to a cave
The cave extends back to form an arch
The arch widens and the roof collapses
A stack is left separated for the headland
Further erosion cause a stump
How are spits formed?
- long shore drift occurring along coast
- coastline changes direction
- waves have to drop sediment forming a spit
How are waves created?
By winds as they blow over the surface of the sea
Strength depends on the wind and fetch
What is a tombolo?
Spits that have continued to grow and joined to an island.
What is a cuspate foreland?
Triangular shape accumulations of sand and shingle
Longshore drift has occurred from two directions
What are sand dunes?
Made up of dry sand blown inland by wind
Forms series of ridges
Vegetation helps stabilise them
What factors affect coasts?
Geology
Vegetation
Sea level changes
Human activities
Explain what a submergent coastline is
When sea level rises
Downward river valleys and glacial valleys
Explain what an emergent coastline is
Falling sea level
Raised beaches
What conditions do coral reefs need to grow?
Temperature - 23-25 degrees C Shallow water for more warmth and light - less than 25 metres deep Wave action - oxygenated salt water Exposure to air - too long they die Sediment - clean water No alge - alge can suffocate Fish to inhabit
Where are coral reefs distributed?
Between the Tropic of Cancer and Capricorn