Coasts Mock Flashcards
what are the coastal systems ?
kinetic (wind and waves)
thermal(sun)
potential(position of material on slopes)
material(marine deposition)
what are the outputs of coastal systems ?
marine and wind erosion from beaches and rock surfaces
evaporation
how many sediment cells are there in uk ?
11
how does wind cause waves ?
wave energy is generated by frictional drage of winds moving across the ocean surface
what is the power equation ?
power = wave height squared x time interval between wave crests
What is a swell wave ?
long wavelength
low height
wave period = up to 20 seconds
what is a storm wave ?
generated locally by high wind energy
short wavelength
greater ehight
shorter wave period
what is the wave height of atlantic vs english channel
5.0 m , 0.6m
what is the wave period of atlantic v english channel
8m , 6m
what is the energy of waves of atlantic and english channel ?
200kW per m, 2.16 kW per m
what is a spilling wave ?
steep waves breaking onto gently sloping becahes
water spills gently forward as wave breaks
what is a punging wave ?
moderately steep waves breaking onto steep beaches, water plunges vertically downwards .
what is a surging waves ?
low angle waves breaking onto steep beaces, waves slide forwrad and may not actually break
what are some features of constructive waves ?
weak backwash
strong swash
low wave in proportion to lengtht
what are some features of destructive waves ?
strong backwash
weak swash
high wave in proprtion to length
breaks downwards with great force
what are tides ?
periodic rise and fall of sea surface.
how are tides produced ?
by gravitational pull of the Moon and to a lesser extent the Sun
how is a high tide formed ?
moon pulls water towards it - also a compensatory bulge on opp side of Earth
where is the low tides ?
between two bulges
When will the highest tide be ?
when moon,sun and earth are all aligned so gravitational pull is at its strongest.
Spring tides
twice each lunar month - high tidal range
Neap Tides
Moon and Sun at rigth angles to each other so gravitational pull is weakest
what is lithology ?
physical and chemical composition of rocks
what is the lithology of clay like ?
weak lithology - not resistant to erosion
bonds between particles that make up the rock are quite weak
what is the lithology of basalt ?q
dense interlocking crystals, high resistant
what causes rip currents ?
tidal motion - or by waves breaking at right angles to the shore
how do rip currents modify the coast ?
create cusps which help perpetuate rip currents, channeling flow through a narrow neck
what are ocean curretns generated by ?
Earth’s rotation and convection
set in motion - movement of winds across the water surface
what do warm ocean currents do ?
transfer heat energy from low attitudes towards the poles
what do cold ocean currents do ?
move cold water from polar regions towards Equator - driven by offshore winds - so less effect on coastal landscapes
what percent of coastal sediment comes from rivers ?
80%
what percent of overall material is supplied to beaches is from cliff erosion ?
70%
Wjat is a discordant coastline ?
layers of rock are perpendicular to the direction of the coats
bays and headlands begin to form
what is a concordant coastline ?
layers of rock are parallel to direction of coastline
outer hard tock - protective barrier to erosion of softer rocjs further inland
what is pressure release ?
overying rocks are removed by weathering and erosion, the underlying rock expands and fracturs parallel to the surface
what is thermal expansion ?
rocks expand when heated and contract when cooled.
If they are subjected to frequent cycles of temp change then the outer layers may crack and flake off
what is salt crystaliisation ?
solutions of sat can seep into pore spaces = salts precipitate forming crystals - growth of crystals creates stress in rock causing it to disintergrate
What is oxidation?
minerals in rock react with oxygen - either in air or water- iron especially susceptible to this process.
what is carbonation ?
rainwater and dissolved CO2 from atmos produce weak carbonic acid - reacts with calcium carbonate in rocks to produce calcium bicarbonate - which is soluble
what is solution ?
some salts are soluble in H20
what is hydrolysis ?
chem reaction between rock minerals and water
how is clay produced through hydrolysis ?
silicates combine with water - produce secondary minerals such as clays
what is hydration ?
water molecules added to rock minerals create new minerals of a larger volume
what are the two types of biological weathering ?
tree roots and organic acids
what is tree roots weathering ?
grow in cracks in rocks and roots - exert pressure putwards
When the trees topple, roots can also exert leverage on rock and soil, bringing them to the surface and exposing them to the surface and exposing them to further weathering
What is organic acids weathering ?
produced during decomp of plant and animal litter - soils water becomes acidic and reacts with minerals in a process called chelation
What type of cliffs does rockfall occur on ?
cliffs of 40 degrees or more
bare cliff face
what is the rpocess of rockfall ?
rocks become detached from slope by physical weathering processes
what is a slide ?
movement along a straight line slip plane
what is a slump ?
common in weak rocks - clay, which also becomes heavier when wet, adding to downslope force
What is pounding ?
mass of breaking wave exerts pressure on rock causing it to weaken
what is settling velocity ?
velocity at which sediment particles are deposited - larger and heavier particles require more energy to transport them
What is horizontally bedded strata ?
undercutting by wave action leads to rockfall, the cliffs retreat inland, parallel to the coast
what is seaward -dipping strata ?
undercutting by wave action remove basal support; rock layers loosened by weathering slide into the sea along the nedding plane.
what is landward dipping strata ?
rocks loosened by weathering and wave action are difficult to dislodge ; the slope profile is gradually lowered by weathering and mass movements.
What are geos formed by ?
action of waves eroding the lower portion of a cliff.
What is an example of a geo ?
Huntsman’s leap in Pembrokeshire - 35m deep and eroded along a large joint in the carboniferous lime stone
What is a blowhole ?
crack or fissure in coastal rock throuh which air and spray is expelled when waves break on the shore
How is a Geo Formed
1) Joints and faults eroded by wave action
2) Hydraulic action important in forcing air and water into the joints + weakens rock strata
3) They initially form as tunnel - like caves running at high angles to cliff.
4) Rock collapse may occur
How are blowholes formed ?
1) part of tunnel-like cave collapses along a master joint it forms vertical shaft that reaches cliff top
2) Storm - large waves force spray out blowhole as plumes of white, aerated water.
what is wave refraction ?
bending of waves in shallow water so they move nearly parallel to shoreline
What percent of beach sediment comes from cliff erosion ?
5%
what percent of beach sediment come from offshore ?
5%
what percent of beach sediment come from rivers ?
90%
What is the process of Longshore Drift?
Material pushed up at 45 degree angle when swash bring it onto coastline
Backwasgh takes it back to sea.
What is the area behind an onshore bar ?
lagoon
What is a tombolo ?
spit connecting island to mainland
What is an example of onshore bar ?
Chesil Beach - connects isle of portland to mainland of Dorset, - stretches for 18 miles
What is a salt marsh ?
coastal ecosystem between land and open saltwater or brackish water that’s regularly flooded by tides.
what are some salt tolerant plants ?
herbs, grassses or low shrubs
how is a salt marsh formed ?
1) zone behind spit becomes sheltered
2) water movement slows. more material deposited
3) deposition forms salt marsh
What is a delta ?
landforms formed at mouth of river, where river meets a body of water with a lower velocity than the river, resulting in the reduction in rivers capacity to transport sediment
How are deltas formed ?
River channel flows over the ground and makes contact with soil, it carries with it sediment,
2) when river encounters another body of water, its velocity decreases and deposits sediment
3) sediment deposited is called aluvium
4) sediment piles up in layers called beds
5) Delta becomes main channel that divided substantial land masses into various streams called distributries
how long is the river nile ?
6,650 km
how big is the river nile’s catchment area ?
2 million km squared
how much annual rainfall does the river nile get ?
600mm
what is the average discharge of river nile ?
less than 3,000 m/s
What is the case study for a low energy coastline ?
nile delta
what is the sediment load of the nile delta ?
30% clay , 40% silt, 30% fine snad
what is the annual average sediment yield of the nile delta ?
4.26 t/ha/yr
Total - 91.3 million tonnes for the whole blue nile basin.
When and where does the Nile delta split into distributaries ?
at Cairo
more than 160km inland
When was Aswan Dam constructed ?
1964
What was the Nile delta like before the Aswan Dam ?
Nile’s annual flood briefly covered much of the delta each year and deposited a thick layer of silty mud.
What is the surface current velocity of nile delta ?
9.26- 13.5 cm /s during summer.
what are the prevailing winds at ther Aswan Dam ?
W, NW, N - 55-60%
NE- 8%
What issues did the Aswan Dam cause ?
imbalance created between two of the major forces affecting the delta - erosion and accretion
Rapid reduction in amount of sediment accreted - from 120 million tonnes/year to trace amounts.
What are the accelerated erosion rates at Aswan Dam ?
high as 148 m/yr
How much is the meditteranean sea rising each year ?
1.2 mm / yr
How long is the Saltburn to Flamborough head coastline ?
60km
What is the high energy coastline case study ?
Saltburn to Flamborough Head
What is the fetch at saltburn to flamborough head ?
1500km
Where are the most exposed parts of saltburn to f head ?
north facing
At saltburn what are the erosion rates of weak shale and clay ?
0.8m per year
At saltburn waht are the erosion rates of sandstones and limestones -
less than 0.1 m per year
What is wave height like at Saltburn ?
exceeded 4m
What sediment cell is saltburn to flamborough head
sub cell 1d of major sediment cell 1
What are the North York moors like ?
rise up to 400m above sea leavel - comprise of sandstones, shales and limestone formed during Jurassic
What is Flamborough Head ?
large chalk head;and - till topped cliffs
What are the cliffs like at saltburn to flamborough head ?
cliff profiles tend to have a vertical face
typically 20-30 m
What are shore platforms like on saltburn to flamboroigh head ?
Robin Hood’s bay - platform slopes at 1 degree , although ramped sections are as steep as 15 degrees
What is the rock type at Robin Hood’s Bay ?
eroded into relatively weak shales with more resistant bands of sandstone either side
what is an example of a stack at Saltburn to Flamborough head ?
Green Stacks Pinnacle ?
how many geos are there on saltburn to flamborough head ?
over 50
where are there blowholes on saltburn to flamborough head ?
north side of slewicks bay
What are emergent landforms ?
landforms shaped by wave processes during times of high sea level are left exposed when the sea level fallswhat
what is a raised beach ?
former shore platforms and their beaches which are at a level higher than present sea level
what are the future modifications of raised beaches (emergent landfroms )?
biological weathering - more signifcant - increasing number of marine organisms - limpets and whelcks
What is a ria ?
submerged river valley , formed as sea level rises
what is the cross section of a ria ?
relatively shallow water - increasingly deep towrds the centre
exposed valley sides are quite gently sloping
what is a fjord ?
submerged glacial valley
steep valley sides
water is uniformly deep, often reaching over 1000m
what is an exxample of a fjord ?
Sogne Fjord - Norway
nearly 200km long U shaped cross section
what is a shingle beach ?
sea level falls - volume of land-based ice grows , large areas of ‘new’ land emerge from the sea.
sediment accumulates on this surface
As the sea levels rose at end of last glacial period - wave action pushed
what are the future modifications of rias and fjords ?
wave processes acting on their sides at present day sea level - reduction in steepness of valley sides of fjords
sea levels predicted to rise by 0.6m in next 100 years, water depth in rias and fjords will increase
what are the future modifications of shingle beaches ?
affected by LSD
shingle may move even further to NE
currently moving at rate of about 17cm /yr
who is responsible for management at Sandbanks ?
Poole Harbour Commissioners
Poole Borough Council
Environment Agency
What is hold the line ?
maintain , sustain or improve existing defences
what is managed realignment ?
existing defences moved to more sustainable positions , usually further inland
what is no active intervention ?
areas of low economic value or/and high environmental value aren’t protected
why is there a need for management at sandbanks ?
high value commercial properties
residential properties - 4th most expensive in world per sqm
blue flag award for water quality
yacht clubs and marinas
How is climate change affecting Sandbanks ?
sea levels predicted to rise by 0.6m in next 100 years
Breach the penninsula at its lowest and narrowest point
What management strats at Sandbanks ?
Rock groynes
Beach recharge
what is beach recharge at Snadbnaks ?
sand dredging from offshore is psrayed onto beach
costs £20 million
what are the house prices at Sandbanks ?
large detached houses - excess of £10 million , many lux apartments over £2 million
where is M-P coastline from Auckland ?
50 km north
what are some uses of sand ?
construction
concrete making
glass manufacture
beach replenishment
what is the pop of auckland ?
1.5 million people
1/3 of NZ total pop
how much of NZ gdp is Auckland ?
35%
in 2015 how many foreign visitors did Auckland have ?
2.3 million
how much sand was mined between 1994 and 2004 ?
165,000 m cubes/yr
where has sand mining ended and continues
ended at Mangawhai
continued at Pakiri Beach
What are the current rates of sand exctraction at Pakiri ?
75,000 m cubed /yr until 2020
when was sand deposited at M-P ?
Holocene Period - 9000 years ago
why is sand a non-renewable at M-P ?
not many rivers, most sand come from offshore
how are beaches affected at M-P ?
they are starved of sediment
become wider and flatter - less effective at absorbing waves
how are foredune ridges effected at M-P ?
undercut by wave action developing steep, seaward facing scarps
what does loss of veg cover mean for M-P ?
more wind erosion
what was the 1978 storm at M-P ?
Caused 28m breach at base of Mangawhai Spit
Shallower water in harbour - threatens seafront community
