Coasts Flashcards
what are the processes affecting coasts?
- weathering
- erosion
- transportation
- deposition
what is dynamic equilibrium?
when inputs and outputs are balanced
what is negative feedback?
negative feedback reduces some of the change by reducing some of the inputs, returning the system to stability
what type of system are coastal environments?
open systems with inputs, stores, flows and outputs
what is positive feedback?
moves the system away from its equilibrium state causing further change
what are high energy coasts characterised by?
destructive waves, long fetches, high rates of erosion, caves, cliffs, wave-cut platforms, arches, stumps
what are low energy coasts characterised by?
constructive waves, shorter fetches, high rates of deposition, sand dunes, spits and bars
what are constructive waves?
- low frequency
- long and low
- swash stronger than backwash= deposition
what are destructive waves?
- erosional
- high frequency
- steep and high
- backwash stronger than swash
what are littoral/longshore currents?
when a flow of water runs parallel to the shoreline in areas where waves approach at an angle, moving water and sediment along
what are rip currents?
strong currents that flow away from the shoreline
what is upwelling?
movement of cold water to the surface
how do tides work?
- water is pulled towards the moon, bringing a high tide on each side of the Earth
- these high tides follow the moon as it orbits the sun
- when the moon, sun and earth line up a spring tide occurs- happening twice a month
- when the moon and sun are perpendicular, a neap tide occurs- twice a month
what is the tidal range?
the difference in height between high tide and low tide
what is abrasion?
where pieces of rock are picked up by waves and hit against the bed, the beach or the cliffs
what is corrosion?
chemical reaction between sea water and susceptible rock eg. limestone
what is attrition?
where piece of bedload are hit against one another
what is hydraulic action?
force of waves being compressed into cracks of the rock. Breaks down rocks and cliff
what is suspension?
small material is picked up and carried by sea water
what is mechanical weathering?
when rocks are broken down without their chemical composition being changed
salt weathering is the main type:
- seawater gets into cracks in rocks
- salt crystals form when the seawater evaporates, these crystals then expand and put pressure on the rock
- the repeated evaporation of saltwater widens the cracks in the rocks until they break apart
what is biological weathering?
biological weathering is when rocks are broken down by living things eg. animals/plants
what is chemical weathering?
when rocks are broken down because of their chemical composition being changed eg. carbonation weathering
what is mass movement?
when rocks and loose material shift down slopes. This happens when gravity overcomes the force supporting the material
what are the coastal transfers?
LSD, onshore and offshore winds and tides
how does LSD work?
- wind approaches the coast at an angle because of prevailing wind direction- this is the way swash moves
- gravity is the only force that acts on backwash, so it falls back to the sea at right angles to the coastline
- because of the difference between the angles of swash and backwash, sediment repeatedly moves in the shape of a right-angled triangle
what is a concordant coastline?
have alternating bands of hard rock and soft rock parallel to the coast
what is a discordant coastline?
alternating bands of hard rock and soft rock at 90° to the coastline eg. Dorset coastline
what is a Dalmatian coast?
made up of offshore islands and coastal inlets running parallel to the coastline eg. lulworth cove
what is usually found on discordant coastlines?
- bays and headlands
- retreating less resistant rock changes shape of coastline and causes wave refraction- increasing rate of erosion= formation of headland features
how is a wave cut platform formed?
- sea attacks base of cliff between the high and low water mark
- a wave cut notch is formed by erosional processes- a dent in the cliff
- as the notch becomes bigger in size the cliff becomes unstable and collapses and retreats
- continues to make platform
how are caves formed?
- cracks are widened in the headland through the erosional processes of hydraulic action and abrasion
- as the waves continue to erode the crack, it begins to open up and hollow out to form a cave
how are arches formed?
- when caves are eroded right the way through the headland, an arch is created eg. durdle door
how are stacks formed?
when the top of an arch collapses a column called a stack is formed
continued erosion of a stack forms a stump
how is a bar formed?
when a spit grows across a bay
how is a spit formed?
- an extended stretch of beach material that projects out to sea and is joined to mainland on one end
- LSD moves material along coastline
- spit forms when material is deposited, waves cannot get past spit
what is a tombolo?
when a spit joins an offshore island
what is an emergent coastline?
- emergent coastlines cause the formation of raised beaches and fossil cliffs caused by isostatic rebound
- a raised beach and fossil cliffs are formed when, following an ice age, the land rebounds. This causes the original height of land to increase.
- this leaves behind a beach and fossil cliff higher than their original position
what is a submergent coastline?
- submergent coastlines cause the formation of rias, fjords and Dalmatian coasts
what is isostatic sea level change?
- isostatic change refers to the level of land, which is also influenced by ice ages
- during an ice age, the weight of the ice forces land to sink
- when the ice age has finished, the melting of the ice causes the land to rebound back up, like a spring
what is tectonic change?
- tectonic change causes land to either rise or sink at the boundaries where tectonic plates meet
- a sudden change in the movement can lead to a rise or fall in the seabed
what is eustatic change?
- eustatic change is the rising and falling of sea levels
- water is stored in the form of ice, ice age=sea levels fall
- ice melting= rising sea level
why are higher sea levels a risk?
- cause higher tides increasing frequency of coastal flooding
- higher tides can remove materials from beaches, leaving cliffs less protected
- increased frequency of storms due to higher energy of the sea
what are the impacts of climate change?
- climate change is changing the frequency and intensity of low-pressure depressions and tropical storms
- rising global temps are causing oceans to warm, triggering these low pressure systems
- this increases the risk of coastal flooding and creates unusual weather conditions
what is a storm surge?
a coastal flood of rising water commonly associated with low pressure weather systems
what are the consequences of coastal recession?
- damage to houses and businesses mean that people are forced to relocate whilst repairs are done and financial support is needed to support this
- many people in less developed countries depend on intl aid
- in developed countries many people cannot get enough insurance to cover potential damages, and many houses lose value as the rate of coastal recession increases
what are groynes?
- stone or wooden fences that stick out at 90° to the coast to stop material being transported by LSD
- they are cheap and effective
- beaches further down get starved
what are sea walls?
- hard concrete walls that deflect waves, refract wave energy back to the sea
- good long-term solution as requires little maintenance
- expensive/ugly
what are revetments?
- angled walls placed just offshore to assist in breaking down the force of the waves
- cost effective
- regular maintenance needed
what is rip-rap?
- a pile of boulders to dissipate the waves energy
- long lasting and relatively cheap
- hazard for people accessing beach
- gaps between rocks allow erosion to cotinue
what is beach nourishment and reprofiling?
- moving material from the upper sections of a beach elsewhere
- slows down waves by widening beaches and so reduces the risk of erosion and flooding
- maintains beach for tourism, supporting local economy
- threatens organisms
what is ICZM?
ICZM (integrated coastal zone management) deals with holistic coastal management strategies
- careful consideration for the most effective management approach
- considers risk to building/local economy/natural environment
what are the benefits of ICZM?
- promotes careful conservation of natural environment
- encourages efficient use of resources
- tries to reduce potential loss to stakeholders who rely on coastal regions for their livelihoods
- inclusive of all parties
what is a ria?
a valley that has been partially submerged by water formed by a substantial rise in sea level or a fall of landmass on a coastline
what is fjord?
an inlet that is long and narrow in shape, with steep cliffs on either side. Formed by the movement of a glacier that cuts rock formations, forming steep ridges either side of a valley and the valley fills with water
