Coastal Environments Flashcards
Wave Types and Features
Constructive: Strong Swash, weak backwash, low frequency (6-8 per min), low height
Destructive: Weak swash, strong backwash, high frequency (10-12 per min), high height
Types of Erosion
Hydraulic Action - force generated by waves hitting the coast
Attrition - rocks carried in a wave erode each other
Abrasion - rocks carried in a wave are hurled at a coast
Corrosion - the dissolving of some rock types (e.g. limestone) due to the slightly acidic seawater
Transportation Methods
Traction - large/heavy material is dragged along the sea floor
Saltation - bouncing of smaller material along the sea floor
Suspension - fine material is suspended in a wave
Solution - material is dissolved in water
Longshore Drift
- wave swash hits beach at the angle of the PWD (prevailing wind direction), transporting material up the beach at that angle
- backwash occurs perpendicular to the beach, carrying the material away from the beach
- process repeats in a zig-zag movement, transporting material up the beach
Types of Weathering
Mechanical - physically breaks up rock (e.g. freeze thaw)
Chemical - breaks rocks down via chemical process(e.g. acidic rain)
Biological - rocks are worn away by living organisms (e.g. growth of trees/plants)
Types of Mass Movement
Slumping - large area of land moves down a slope in one piece, occurs in weaker rock types (e.g. clay), leaves behind a curved surface
Sliding - Movement of large blocks of detached rock downhill
Headlands and Bays
- formed in areas of discordant geology (alternating sections of hard and soft rock types perpendicular to a coastline.)
- softer rock types (e.g. clay) are eroded back, forming a bay
- harder rock types (e.g. limestone) is left protruding out to sea as a headland
Cove formation
- forms along concordant stretches of coastline (when alternating rock layers are parallel to the coastline.)
- layer of resistant rock is eroded, until softer band of rock behind is breached
- further wave action will erode the soft rock quickly, resulting in a circular cove forming with a narrow entrance to the sea
Wave-Cut Platform
- is a wide gently sloped surface found at the base of a cliff
- waves erode the zone between the high and low water mark, forming a wave-cut notch
- erosion further extends the notch back into the cliff
- causes undercutting, resulting in the collapse of the face of the cliff
- toppled cliff face forms wave cut platform as process repeats
Cave, Arch, Stack, Stump
- weaknesses in headland are exploited by erosional processes, e.g. hydraulic action
- further erosion causes the cracks to widen and caves to form
- cave will increase in size, and as headland retreats, an arch will break through
- stability of arch weakens due to more erosion, causing parts of it to collapse, forming a stack
- stack is then undercut via wave action, collapsing and forming a stump.
Beaches
- formed in sheltered areas (e.g. bays)
- occurs when swash is stronger than the backwash
Spit formation
- change in direction of coastline causes deposition of sediment
- increased friction causes more deposition, building up a spit to sea level, extending in length.
- changes in wind direction can cause a hooked end
- salt marshes or mud flats form behind spits as they are sheltered areas
Bar
- a spit that grows across a bay, connecting two headlands together
- different to tombolo, as it connects mainland to mainland
Lagoon
- small body of water cut off from the sea
- may form behind a bar
- can be filled with sediment, don’t last forever
Tombolo
- a spit that joins mainland to an island
- different from bar
