eq2 Flashcards
hurricanes
tropical storms found in the Atlantic Ocean
cyclones
tropical storms found in the Indian Ocean
typhoons
tropical storms found in the Pacific Ocean
tropical storms
storm event that has very low atmospheric pressure
- leads to evaporation
- air rising
- cooling and condensing
- cumulunimbus clouds
- precipitation
wave formation
- wind blows across surface of ocean/lake
- friction
- water particles move in orbital motion, though not forward = oscillation waves
- wave energy moves in a column (up to down in circles)
- energy is passed forward
- as wave travels across, bottom drags along ocean floor
- creates friction
- upper part moves faster than rest as depth decreases
- upper part tilts forward as the dragging becomes stronger
- makes wave break in the surf zone
factors that affect strength of a wave
- wave height
- fetch
- wave refraction
- depth (affects height)
- wind speed
- hydro-meterological events
examples of fetch
- atlantic large
- mediterranean small
examples of wave refraction
- st David’s head
- st Ann’s head
- st Bride’s bay
characteristics of constructive waves
- low-surging waves
- long wavelength
- strong swash, weak backswash
- beach gain (constructive)
- low flat wave height
- strong swash pushes sediment up the beach
- weak backswash leads to deposition of sediment at the top of the beach
- 6/10 minutes
- gentle gradient
characteristics of destructive waves
- high energy waves
- short wavelength
- weak swash, strong backswash
- beach loss (destructive)
- high wave height
strong backswash erodes material - 11/15 minutes
- steep waves
Hydro-meterological events
tropical storms, flooding, extreme weather
berm
created especially in macro tidal areas such as Cornwall in Atlantic
erosional processes; abrasion
- as waves advance, pick up sand and pebbles from seabed.
- then, break at base of cliff. transported material is hurled at the cliff foot- chips away rock
erosional processes; hydraulic action
- when wave advances, air is trapped + compressed
- when retreats, compressed air expands again
- continuos process weakens joints and cracks in cliff
- force of rock can also hammer a rock surface.
- at high velocities, bubbles form in water + collapse, they erode by hammer-like pressure effects.
erosional processes; corrosion
- when cliffs are formed made by alkaline rock (chalk or limestone), or alkaline cement that bonds the rock particles together, solution containing weak acids in seawater can dissolve them
attrition
- gradual wearing down of rock particles by impact and abrasion
- pieces f rock are moved by waves, tides and currents which gradually reduces their size and makes stones rounder and smoother.
how do waves and lithology influence erosion
- in booklet
wave refraction
- when the undersea topography causes the wave fronts to slow, bend and aim to break parallel to shore
- leads to energy being concentrated on headland (hence more ero)
- leads to lower energy in bays (hence depo)
if waves break at angle within the bay, LSD occurs
wave cut notch
- erosion caused when waves break against the foot of a cliff. (abrasion, HA, corrosion)
- undercutting formed = WCT
- eg: flamborough head, Yorkshire
wave cut platform
- as undercutting gets bigger, rock above it too heavy + due to gravity unstable + collapses
- repeated = cliff retreats
- leaves behind a wave cut platform
- as retreats, bigger WCP
- eg: southerndown, South Wales
cliffs
- constant wave action and erosion against cliff foot = steep profile and retreats.
- steepest where rock strata are vertical or horizontal or have almost vertical joints.
- gentlest = rock dips towards or away from sea
- eg: Near Eastbourne, West Sussex
caves, arches, stack stumps and blow holes
- caves = joints + faults eroded by abrasion + HA
- if overlying rock collapses = blowhole
- if 2 caves join or single cave is eroded through headland = arch
- top of arch unstable and collapses = stack
- continue to erode + collapse = stump
- eg: on Great Ocean Road, Australia
traction
relatively large and heavy rocks are rolled along the seabed
saltation
smoother and lighter rocks bounce along the seabed
suspension
fine, lighter sediment carried in water column
solution
when disolved sediment is carried
what influences sediment transportation- tides + currents
- caused bu gravitational pull of the moon
- UK has 2 high tides and low tides a day
- level of tide will determine at what height on foreshore and back shore processes such as depo will be occurring
- higher tidal range leads to powerful tidal currents, can become rather strong in estuaries and narrow channels
what influences sediment transportation- angle of wave attack and LSD
- LSD main transport process
- strongest LSD = waves approach beach 30 degrees angle
- swash pushes material up the beach
- backswash= at 90 degrees, due to gravity, pulls away
- so, sediment in zig zag up the beach
- wind and wave direction will determine direction of LSD
- refraction around headlands can reverse LSD direction
drift aligned beaches
- sediment transferred along the coast by LSD
- wave crests break at an angle to the coast, so there is consistent LSD + material moves significantly along the beach.
swash aligned beaches
sediment doesn’t move much along the beach.
- wave crests approach parallel to the coast, so there is limited longshore movement of sediment
bayhead beach
- a seas aligned feature, where waves break at 90d to shoreline and move sediment into a bay, where a beach forms.
- due to wave refraction, erosion is concentrated at headlands and the bay is an area of deposition.
