test 2 Flashcards
coastal processes
important discipline in marine science which examines this important real estate and the processes which constantly change and alter the sediment which largely overlies much of the ground of the region
what do we do to examine our coasts
look at physical boundary of coast (bedrock) and the sediment. evaluate wind, waves, and tides
wave
undulation in ocean surface that results from some disturbing force (wind, seismic force, gravitional force)
how does water move in waves
moves in circular orbits that decline with depth
wave height
distance from trough to crest
what is twice the waves amplitude
height
period
time taken between when any part of a wave passes a fixed point and when the same part of the next wave passes it
wavelength
distance between same parts of two waves
frequency
number of waves that passes a fixed point. inverse of the period
wave classification
based on size, source of energy, or how wave interacts with the ocean floor
wave size
length, height, or period. 10th of a second to 24 hrs
energy source
wind (most common), tectonic energy, kinetic energy (landslides or meteors), gravitational and centrifugal from moon and sun
interaction with ocean floor
how energy is absorbed and reduced.
do deep water waves interact with teh ocean floor
no
shallow water interaction
interacts with ocean floor, changes shape and loses speed over time
capillary waves
light breezes, <2cm
wind waves
consistent wind, 1.5-900 meters
tsunamis
tectonic forces, landslides, meteors. 20km - 500 km
tides
gravity, centrifugal force. 18,000 km
what is the typical wind wave
between 60 and 150 meters long, around 3 meter high. most common wave in ocean
speed of wind-generated surface waves is controlled by
wind velocity, wind duration, fetch
wind velocity
generating force, speed of the wind blowing
wind duration
limiting force, time the wind is sustained in that area
fetch
limiting force, distance over which the wind is consistently blowing
fully developed sea
when wind blows sufficiently long in same direction. creates waves in maximum size, speed, and period
shallow water waves are
very long waves that interact with the water even at the great depths of the open ocean
shallow water waves can also be
waves in shallow water reached by smaller waves formed offshore
deepwater waves
waves that progress through the ocean and don’t interact with floor. smaller waves.
wave base =
1/2 wavelength
wave base
depth in the water above which a passing wave disturbs the water. below which the water is undisturbed.
what is the wav ebase determined by
energy of the wave, measured by its wavelength. the longer the wavelength, the deeper the water is disturbed
speed of a deepwater wave
C(m/s) = L / t, or 1.57 * t (length / period)
speed of a shallow water wave
c = 3.16 (sqrt Depth)
deepwater waves speed
celerity (c) = L / t, or swrt(gD)
g is graviational force (9.81 m/sec^2) and D is depth in meters or C = 3.13sqrtD
tsunamis
very large powerful waves produced by tectonic events
because of tsunamis ___ length, tsunamics are considered ___ water waves
extreme, shallow water
what happens when waves approaches shoreline
speed and wavelength decreases, height increases, orbitals are more flattened, pointed crests, wide troughs.
why do waves slow down in shallow water
they feel the bottom and there’s more friction
waves break when
gets steeper, will break at ratio of 1:7 (height:length)
spilling breakers
low steepness over gentle slopes.
where do spilling breakers occur
east coast and gulf coast
plunging breakers
steeper waves over moderate slopes. energetic tall waves
where to plunging breakers occur
pacific coast
surging breakers
beach slope exceeds wave steepness. doesn’t curl and break, runs up against the shore and produced foam.
wave refraction
the part of wave in deeper water continues at maximum speed while part in shallower water begins to slow, eventually as the entire wave approaches the shoreline the speed evens out
swash
water drives onto shore in direction of winds
backwash
water returning perpendicularly to ocean
west coast characteristics
narrow shelf, steep slope, inward prevailing winds
east coast characteristics
broad shelf, gradual shelf, outward prevailing winds
tides
periodic short term changes in ocean surface’s height. caused by gravitational pulll of moon and sun and motion of the earth
pytheas (greek navigator)
first wrote about hte connection between position of the moon and height of the tide
isaac newton
determined that gravitational pull is proportional to their size, but inversely proportional to the suare of the distance between them
