T4 - Coasts Flashcards
What is erosion?
The land wearing away over time by waves, wind and water and the removal of material.
Explain cave, arch, stack, stump
1) A crack opens due to hydraulic action
2) Widens and becomes a cave
3) Breaks headland forming an arch
4) Arch is eroded and collapses to form a stack
5) Stack is eroded and forms a stump
Hard rock coasts
- consist of resistant rocks
- igneous ex. granite
- sedimentary ex. limestone and chalk
- Lulworth Cove, Dorset, East Yorkshire
Soft rock coasts
- less resistant rocks
- sedimentary ex. clays
- Holderness coastline, Christchuch Bay
Concordant coastlines
- rocks are parallel
- one type of rock
- forms coves
ex. Lulworth Cove
Discordant coastlines
- rocks are perpendicular
- many types of rock
- forms headlands and bays
ex. Holderness Coastline
What causes waves?
Caused by wind dragging on the surface of the water
What is the fetch?
Length of water the wind blows over
Swash
Water that rushes up the sand when a wave breaks
Backwash
Water runs down the sand after a wave breaks
What are tides?
Result of rise and fall in sea level
Two types of coastline
Concordant and discordant
Two types of waves
Destructive and constructive
Constructive waves
- small spilling waves
- long wavelengths and low amplitudes
- strong swash
- sand is deposited
Destructive waves
- tall, plunging waves
- short wavelengths and large amplitudes
- strong backwash
- sand is eroded
Headlands
Hard rocks have a high resistance to erosion, eroded slowly
Bays
Soft rocks have low resistance to erosion, eroded quickly
What is longshore drift?
- sediments being transported along a coastline
- when waves break at an angle
What factors make coastal flooding worse?
- climate change
- building
- shape of sea
- geology
What is hard engineering?
Man made structures to control the flow of the sea, reduce flooding and erosion
What is soft engineering?
Natural methods to reduce effects of flooding and erosion
Groynes
- placed at right angles to trap sand from longshore drift
- can cause erosion further down the coast
- ugly and expensive
Sea walls
- concrete walls that absorb wave energy and protect cliffs
- reflect waves back to sea
- can create strong backwash
- expensive
Rip rap/ rock armour
- large boundaries absorbs wave energy
- relatively cheap
- natural looking
Gabions
- steel mesh cages with boulders
- cheap
- ugly
Beach replenishment
- sand is added to replace washed away sand
- beach absorbs wave energy
- have to do regularly
- cheap
Dune stabalisation
- roots of plants bind to sand and dunes develop
- cheap if maintained
What is climate change?
A significant change in Earth’s climate over a long period
Evidence that earth’s temperature has changed
- ice cores
- tree rings
- historical sources
Impacts
- changes weather patterns
wet areas get wetter and dry areas get drier - storms. floods, droughts
Contributing factors to climate change
- forest fires
- melting polar ice caps
- deforestation
- combustion
What are greenhouse gases?
Gases in the earth’s atmosphere that trap heat
Examples of greenhouse gases
- carbon dioxide
- methane
- halo carbons
What is the greenhouse effect?
Energy from host star heats planet but greenhouse gases prevent from the heat returning back to space which results in a warmer planet
What is a storm surge?
Rising of sea as a result of wind, waves and low pressure
- atmospheric pressure changes due to a storm
What is storm frequency?
Climate change results in them becoming more frequent
Storms give water more erosional power
Rising sea levels
- low-lying coastal areas
- increasing high tides -> more floods
- increase in erosion
- beaches more narrow
Case study: Holbeck Hall
- cliff collapsed in Scarborough, North Yorkshire, 1993
- geology: sedimentary
- 1M tonnes of land displaced less tourism, loss of livelihoods
Don’t build on land nearby sea
Christchurch Bay
- on UK’s south coast
- big waves + mass movement
- cliff collapses, unsafe, loss of homes, insurance is impossible, expensive
Spits
- sharp bends
- LD transports sand and shingle past bend and deposits into sea
- strong winds and waves can curve the end
- material accumulates
- mud flat/salt marsh
Bars
- when a spit joins two headlands together
- bar cuts off bay from the sea
- lagoon forms behind bar
Sand dunes
- when sand deposited by LD moved up by wind
- obstacle changes wind speed
- colonised by plants
- sand accumulates
