coastal processes Flashcards
tides
waves with extremely long wavelengths and periods that travel across the ocean and are modified by the geomorphology of the coastline
Tsunami are tidal waves.
TRUE or FALSE
FALSE
everywhere experience equal tides.
TRUE or FALSE
FALSE, influenced by location of the ocean basins and position of the land masses
semi-diurnal tide cycle
2 similar high and low tides
diurnal tide cyle
1 high and 1 low tide per day
on tidal charts, how are different height high tides distinguished?
higher high water and lower high water
mixed tide cycle
no pattern
most places on earth experience how many neap and spring tides per month
2
tidal range
difference between neap (lowest low) and spring tide (highest high)
how many days after a spring tide will a neap tide occur?
7 days
what is the arrangement of planets in a spring vs neap tide?
spring: moon, earth, sun all aligned.
neap: moon 90 degrees to sun and earth
king tides
full moon and closest orbit to the earth coinciding. Results in exceptionally high tidal ranges.
king tide and deep low pressure weather system can result in
widespread coastal flooding
tide terminology: HAT = MHST = MHNT = MIN HT = MIN LT = LAT =
tide terminology: HAT = high astronomical tide MHST = mean high spring tide MHNT = mean high neap tide MIN HT = minimum high tide MIN LT = minimum low tide LAT = lowest astronomical tide
where is the maximum shore width?
at HAT and LAT
3 things affecting height, wavelength and period of WAVES
- wind speed
- length of time wind blows
- fetch
define fetch
distance the wave has travelled across open water
sea state
describes the prevailing wave climate
3 main types of wave
- ocean swell
- storm waves
- nearshore waves
at what depth below a wave is the water unaffected by wave energy?
half the wavelength deep
ocean swell into breakers
Ocean swell is created by distant storms in the ocean. The swell generally has a long wavelength and low amplitude. As the swell approaches the coastline, water depth decreases and the wave height increases. As the height increases, the front of the wave steepens due to a speed reduction caused by friction with the seabed. As the wave continues to slow and become nearshore waves they reach shallow water and the oscillation becomes so great that the wave front collapses as breakers. The morphology of a breaking wave is dependent on the nearshore bathymetry
plunging breaker vs spilling breaker
steep offshore slopes = plunging
gentle slope = spilling
storm surges
caused by very low offshore pressure systems. Combined with winds makes for a very destructive situation
how deep below a wave is the water affected, leading to sediment mobilisation
water depth = 2 x wavelength
