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.