lesson two - coastal enviroments and energy Flashcards
(19 cards)
what is foreshore?
area between the high and low watermark and most important for marine processes.
what is backshore?
area between the high water mark and the cliff/beach edge with limited marine activity.
what is inshore?
area between low water mark and the point where waves cease to influence the land beneath.
what is offshore?
area beyond the point where waves impact the seabed and only deposition occurs.
what is the swashzone?
area where water washes up the beach after the waves break.
what is the nearshore?
area that extends seaward from high water mark to where the waves break.
what is the surfzone?
area between where waves break and move into the swash zone.
what is the breakerzone?
area where approaching waves begin to break.
what is energy?
the force needed to drive the coastal system e.g tides,winds,waves
how does wind impact the coastal system?
- creates waves through the energy transfer as they blow across the seabed creating frictional drag
- the direction of wind (prevailing winds) impacts erosion and approach of wave
- fetch is the length the wave has traveled before it hits coast
define these extra key words for coast and energy?
swash - movement of water up the beach
backwash - movement of water down the beach
crest - top of wave
trough - lowest point of wave
wave height - difference of the crest height and trough
wave frequency - time it takes to move past fixed point
wave length - distance between two crests
what are constructive waves and how do they form?
weak winds create waves with long wave length and short height
top of wave travels faster and due to friction it breaks
swash rapidly looses volume and energy so the water infiltrates into the sand therefore the backwash is week and cannot remove any sediment
overtime berms are created
what are destructive waves and how do they form?
winds are strong creating tall waves and a short length
top of wave travels faster than base causing it to steepen and due to friction it breaks and plunges
causing a stronger backwash as there is little forward moment
the breaking waves also prevent swash from the next waves
overtime this creates a steeper beach profile.
what is wave refraction?
as waves approach the headland it drags shallow water near the headland ( increasing the wave height and steepness)
causing the wave to speed up and bend towards the headland in which increases erosion
as they hit the headland the cause a subtle slr and loose energy spilling into the bay which creates LSC ( long shore current ) running parallel to coast transporting material.
what is a longshore currents?
waves do not hit perpendicular but at an angle this create a flow of water parallel to the shoreline moving sediment along the surface.
what are ripcurrent?
strong currents that move away from shoreline , developed when the piled up seawater can escape and when it eventually does through the breaker zone it’s powerful.
what is upwelling?
the movement of cold water rising as the denser cold water replaces the warmer surface water creating a cold current that makes up part of the global ocean circulation currents.
what are tides?
the periodic rise and fall of the sea due to the gravitational pull of sun and moon ( moon stronger )
the moon pulls water towards it creating high tides and a bulge is created on the other side to compensate (low tide)
spring tides - occur twice a lunar month when moon sun and earth aline creating most destructive seas.
what are tidal surges?
occur from meteorological conditions
a rise in wind increases water levels above average
north sea particularly vulnerable due to depressions
