Inputs Flashcards
fetch
the distance of open water over which the wind blows uninterrupted by major land obstacles
the length of fetch determines…
the magnitude and energy of the waves reaching the coast
waves are created by…
the transfer of energy from the wind blowing over the sea surface (frictional drag)
wave frequency/period
the time for 1 wave to travel the distance of one wavelength or the time between 1 crest and the following crest passing a fixed point
swash
the rush of water running up the beach
backwash
any water running back down the beach towards the sea
waves are driven by
the wind
negative feedback
constant cycle of: constructive waves build up beach (steeper profile) which encourages waves back as destructive, with time destructive moves material towards sea, reducing angle, encouraging more constructive waves
wave refraction
when waves approach a coastline that is not regular shape, they are refracted and become increasingly parallel to coastline
current
the permanent or seasonal movement of surface waves in seas and oceans
longshore currents (littoral drift)
most waves approach at an angle to coastline so generates flow of water running parallel to shoreline
rip currents
strong currents moving away from shoreline developed when seawater is piled up by incoming waves
upswelling
movement of cold water from deep in the ocean towards surface as more dense cold water replaces the warmer surface water and creates nutrient rich colder ocean currents
tides
the periodic rise and fall in the level of the sea
cause of tides
gravitational pull of sun and moon (moon has greater force as closer) so moon pulls water towards it creating high tide and compensatory bulge on opposite side of Earth
as the moon orbits the earth…
high tides follow it
tidal range
the difference in height of seawater at high and low tide but not fixed due to tidal cycles
tidal range determines…
upper and lower limits of erosion and deposition
the time each day the littoral zone is exposed and open to subaerial weathering
low tidal ranges
along coast of Mediterranean Sea which restricts wave action to narrow width
high tidal ranges
parts of British Isles which gives wide zone of wave attack so forming wide wave-cut platforms
macrotidal
more than 4m
mesotidal
2-4m
microtidal
less than 2m
sources of sediment
streams/rivers into sea estuaries cliff erosion offshore sand banks material from biological origin *shells
sediment cells
distinct areas of coastline separated from areas by well-defined boundaries, regarded as closed systems, vary in size
concordant coastline
where the rocks lie parallel to the coast
disconcordant
where the rocks lie perpendicular to the coast
changes in sea level in last 10,000 years
rising an average 0,42 to 0,48 inches a year, started declining in 2010 and 2011 locked up as snow/ice
rias
drowned river valleys
fjords
drowned glacial valleys
dalmatian coast
When the valleys are flooded by the rise in sea level, the tops of the valleys remain above the surface of the sea and appear to be a series of islands that run parallel to the coastline
raised beaches
areas of former wave-cut platforms at a level higher than current sea level
marine platform/terrace
formerly submerged land exposed
effect of wave refraction on headlands
waves drag in shallow water, wave becomes high/steep/short, part of wave in deeper water moves faster, wave bends, low-energy wave spills into bays as most energy concentrated on headland
