coasts Flashcards
hydraulic action coasts
water forced into cracks compressing the air inside by forcing rock apart
corrasion coasts
loose rocks thrown against the cliff by waves
attrition coasts
loose sediment in water constantly collides with other sediment becoming smaller and rounder
corrosion coasts
acids in seawater dissolve material of cliff rocks
traction coasts
larger pebbles and cobbles rolled around seabed
saltation coasts
small pebbles bounced along seabed in “leapfrog motion”
suspension coasts
fine sediment carried as suspension in water
solution coasts
dissolved material carried along in solution
formation of headlands and bays
-hydraulic action
-corrasion
-corrosion
-hard and soft rocks present alternately
-joints (bedding planes)
-differential erosion: soft rocks erodes more rapidly forming bays and hard rock erodes less rapidly forming headland
(also can be crack to stack)
what is wave swash
wave that approaches beach
what is backwash
wave that leaves the beach into the sea
constructive waves property
- lower energy
- stronger swash
- less than 8 waves per min
- lower height
- deposit material on the beach
- longer wavelength
- further distance between wave crests
- spill forward gently
destructive waves properties
- higher energy
- stronger backwash
- 13-15 waves per min
- greater height
- erode beach material
- shorter wavelength
- smaller distance between
- wave crests
- plunge forward
what is longshore drift
- prevailing winds cause waves to approach at an angle to the shore
- swash carries loose material up the beach at an angle (in the same direction as prevailing wind)
- backwash takes material back out at 90 deg
- zigzag motion moves material along the beach
(coast) spit properties
- long and thing
- curved hooked end
- stretches partly across estuary
- made of sand shingle
- low in height (just above sea level)
- salt marsh develops behind spit
formation of sand dunes
- wind blows from the sea
- wind picks up sand particles
- wind drops them around an obstacle
- dunes increase in size due to more build up of sand (deposition)
- colonization by vegetation anchors sand forming sand dune
conditions required for coral reefs
- warm water (18-27 C)
- shallow water (less than 60m)
- water free from sediment
- plentiful supply of oxygen in water
- plentiful supply of plankton
- calm water (no strong currents)
- pH 8 or above
- high salinity
what are mangrove swamps
areas of vegetation found along sheltered tropical coastlines and estuaries
conditions of mangrove swamp
- temp above 20C
- large area between high and low watermark
- salty water
- no strong waves or tidal currents
mangrove adaptations
- specially adapted roots to filter salt
- roots prop tree up and take in oxygen in low tide
coastal hazards
- coastal erosion
- coastal flooding
- tropical storms
- tsunamis
- cliff collapse
what is a sea wall
large walls constructed from concrete, steel or stone located along the shoreline of a beach
advantages of sea wall
-protects cliffs from upland erosion and is a barrier to flooding
disadvantages of sea wall
eaves can erode the wall defeating its purpose, and is expensive to implement and maintain
what is a groyne
wooden fence-like barriers built at right angles at the beach
groyne advantages
prevents longshore drift, flooding and erosion, allows beach to build up
groyne disadvantages
can create erosion further down the coast
is unattractive and expensive
what is a gabion
bundles or rocks in metal mesh located at cliff bases
gabion advantages
reduces impact of waves
gabion disadvantages
inexpensive hard engineering structure, but not very effective or attractive
what is a revetment
slanted structures made from concrete, wood or rocks along a cliff
revetment advantages
prevents cliff erosion as it absorbs the waves energy
revetment disadvantages
expensive to implement
can create a strong backwash
what is a coastal barrage
partly submerged dam-like structures that can control tidal flow
coastal barrage advantages
create a more consistent water level, can be used to create hydroelectricity
coastal barrage disadvantages
has a strong impact on the enivronment and expensive to maintain and implement
what is rock armor/rip rap
large boulders or rocks piled up on a beach infront of a cliff or seawall
rock armor/rip rap advantages
absorbs energy of waves and helps build up beaches
rock armor/rip rap disadvantages
expensive to implement and maintain
what is beach nourishment
beach made wider using sand and shingle
advantages of beach nourishment
increases distance a wave has to travel, slowing it down and preventing erosion
disadvantages of beach nourishment
sand and shingle need to be sourced from somewhere else, usually by dredging
requires a lot of maintenance and can be costly
coastal opportunities
- water supply and irrigation
- farming
- tourism
- settlement
- transport
- ports and trade
- fishing
- industry
