energy in coastal systems Flashcards
wind role (5)
primary source of energy
-wind speed high and uninterrupted = high wave energy
-prevailing wind determines direction waves approach and direction sediment transport
-fetch (distance blows) influences energy of waves
-influences wave formation
-can pick up sediment from coast and use it to erode other features
waves formation
primary agent in shaping the coastline
wave approaches coast and it becomes shallower
friction with seabed slows base of wave
crest continues move forward and rise
elliptical orbit
wave steepens and breaks and moves up beach as swash
constructive waves
low wave height
long wavelength
low frequency (6/min)
spill
weak backwash
move material up beach - gentle slope beach
forming berms (ridges)
destructive waves
high wave height
short wavelength
high frequency (10/min)
plunge
strong backwash
erodes material - steep beach
may project shingle up beach forming ridge called storm beach
negative feedback of waves
constructive builds beach making steeper
more destructive waves
reduces beach angle
etc
what is wave refraction
waves drag in shallower water near headland forming destructive waves which erode headland
part in deeper water moves faster so bends
wave concentrated on headland causing erosion
deposition on beach
waves pile on headland forming longshore current
what is a current
permanent or seasonal movement of surface water in oceans
longshore current is
flow of water parallel to shoreline
due to waves approaching at angle
rip current is
strong currents moving away from shoreline
as sea water piles up along coastline
flow out through breaker zone where change direction coast
dangerous
upwelling is
cold deep ocean water replacing warmer surface water
creates nutrient rich cold ocean currents
what is a tide
periodic rise and fall in sea level
*** how do tides form
moon pulls water towards it creating a high tide and therefore a compensatory bulge of the oceans surface water on the other side of earth
in between experiences low tide
***spring tide
moon sun earth all in line
produces high highs and low lows
large tidal range
***neap tide
moon and sun perpendicular to earth
low highs and low lows (10-30% lower)
small tidal range
what is tidal range
vertical difference between high tide and low tide
larger the range the greater the limit of erosion and deposition
amount of time littoral zone exposed each day increases subaerial weathering
med low range
britain high range so forms wide wave cut platforms
