Coasts Flashcards
When backwash > swash = _____
Destructive wave
When swash > backwash = _________
Constructive wave
What is a destructive wave
Formed by strong winds, high energy levels. Erodes beach material
What is a constructive wave
Calmer weather, less powerful, don’t break as violently.
More material carried up beach than down
What causes a tidal bulge
When the sun and moons gravity pull on earths ocean waters
Abrasion
Waves pick up material and hurl them at base of cliff
Hydraulic action
Air trapped, compresses, pressure of water weakens rock and breaks
Solution/ corrosion
Acids in sea dissolve rocks e.g. - chalk and limestone
Attrition
Waves smash rocks and pebbles on shore into each other - they break and gradually get smaller
Fetch
Length of water waves travel
What are sub aerial processes
Land based which alter shape of coastline. Combo of weathering and mass movement
Different types of weathering
Freeze thaw action
Exfoliation
Biological weathering
Chemical weathering
Exfoliation.
Respected action of heating and cooling rocks causing them to shed off layers
Biological weathering
Plant seeds get into cracks and begin growing, put pressure on rocks causing them to fracture
Chemical weathering
Hydrolysis - splitting of materials due to reactivity with water
Oxidation - Rusting
What are the different types of mass movement (5)
Rockfalls Soil creep Landslides Rotational slumping Mudflow
Rockfalls
FTW breaks rock into smaller pieces and this can free fall
Soil creep
Damp soil moves slowly downhill due to increase in mass OR as a result of freezing and thawing
Landslides
After being soaked with water, cliffs made from soft rock will start to slip due to rock being lubricated
Rotational slumping
Heavy rainfall makes rock heavier due to absorbing water and lubrication
Mudflow
Steep slopes, saturated soil and little vegetation - rapid movement of mud downhill
Formation of a cave, arch, stack, needle and stump
Cave:
Weaknesses in the rock gets eroded by hydraulic action and abrasion
Arch:
More hydraulic action and abrasion also sub serial
Stack:
Arch collapses bc too heavy - detached stack
Needle:
Thinner stack
Stump:
Eroded needle
Formation of wave cut platform
Starts as wave cut notch, waves erode notch by high water mark erosion (hydraulic action + abrasion) + sub aerial (FTW) + mass movement (rockfalls)
*Explain how hydraulic action, abrasion, FTW and rockfalls occur.
Cliff retreats, wave cut platform develops and build up in beach material - sand.
What is a blow hole
Roof of cave collapses, incoming waves force air to rush vertically or water to spout intermittently
What is a geo
Inlet in face of cliff - created by the wave driven erosion of cliffs along faults and bedding planes in rock
Long shore drift
Sediment is carried up beach by awash and backwash
Solution
Minerals dissolved in sea water
Suspension
Small particles carried in water
Saltation
Load bounced along sea bed - small pieces of shingle
Traction
Pebbles/ larger sediments rolled along sea bed
Formation of spit
Spit is stretch of land that joins the main beach at one end
Long shore drift and direction of prevailing wind, sediments carried up beach by smash and backwash. Deposited above the high water mark and becomes short extension of beach material connected to main beach.
Longer spit created, second most dominant wind creates hook. Fastest river current helps prevent spit from expanding to form a bar. Behind spit - mud flat forms. When conditions become possible for algae and vegetation to grow, salt marshes form.
Salt marshes can act as a natural coastline defence, trapping sediments and creating shallows near coast - slow down and remove energy from storm waves.
Coastal management (7)
Sea wall - Built along front of cliff to protect settlement
Groynes - To help prevent longshore drift
Offshore rock groynes - Change direction of waves and reduce longshoremen drift
Rip rap/ rock armour - Big boulders Placed along base of cliff to absorb energy from waves
Revetments - Wooden slatted barrier absorbs energy from waves
Gabbions - Rocks and boulders invaded in wired mesh to absorb energy from waves
Beach replenishment - Making beaches higher and wider by bringing sand in from somewhere else
