chapter 8- waves Flashcards
generating force
Responsible for creating a disturbance on the water surface (wind, earthquakes, water displacement) creates ripples or capillary waves.
restoring force
Responsible for returning the water suface to an undisturbed state (gravity and surface tension)
cats paw
Restoring force - small patches of waves that darken the surface, move quickly, and die out rapidly.
Majority of the waves seen on the ocean or lake are..
gravity waves
Crest
Part of the wave that is elevated the highest above the undisturbed sea surface (aka equilibrium surface)
Trough
Part of the wave that is depressed the lowest below the undisturbed sea surface. It is flatter than the crest.
wavelength
Shortest part of the waveform that, if repeated multiple times, will reproduce the wave slope. This distance between 2 wave crests.
wave height
Vertical distance from the elevation of the crest to the depth of the trough
wave frequency formula
Is equal to one half the wave height (vertical distance from crest to undisturbed water or trough to undisturbed water)
wave shape
Equal to the wave height divided by the wavelength.
wave period
The time required for the wave crest “A” to reach point “B” from a staionary point.
wave frequency
The number of wave crests passing point “A” each second. (The reciprocal of the wave period.)
orbit
In waves, the path followed by the water particles affected by the wave motion.
progressive wind waves
Wave that moves or progresses in a certain direction.
storm center
An area of origin for surface waves generated by the wind; an intense atmospheric low pressure system.
forced waves
When waves are being generated, they are forced to increase in size and speed by the continuing input of energy.
free waves
Move at speeds controlled by their periods and wavelengths. (tsunami)
sorting/dispersion
waves with different lengths and velocities gradually move through and ahead of the shorter, slower waves. (Aka dispersion)
wave trains
Progressions of similar or identical waves with approximately the same period and speed
swell
Uniform, free waves
wave height is controlled by…
Wind speed
Wind duration
Fetch (the distance over water that the wind blows in the same direction)
episodic waves
An abnormally high wave that occurs because of a combination of intersecting wave trains, changing depths, and currents.
wave steepness
Ratio of wave height to wavelength.
speed of waves
The wavelength divided by the period.
shallow water wave
Wave with a depth of less than 1/20 of the wavelength. Set water particles in elliptical motion.
diffraction
Process that transmits energy laterally along a wave crest.
breakers
Sea surface water wave that has become too steep to be stable and collapsed.
four types of breakers
1.Plungers -Moderately steep slopes. Crest out runs the rest of the wave, curves over the air below it.(Surfing waves.)
2.Spillers- Very gentle beach slopes. Last longer, they lose energy gradually.
3.Collapsing Breakers- Steep bottom. Wave collapses over lower part of wave w/ little foam & splash.
- Surging Breakers- Steep slope. Wave steepens & leans forward, but doesn’t collapse. Runs up on beach w/out much
splash.
rip current
Strong surface current flowing seaward from shore; the return movement of water piled up on the shore by waves and wind.
internal wave
Wave created below the sea surface at the boundary between two density layers. They are slower than surface waves.
standing waves
Do not progress; they rise and fall vertically
node
Point of least vertical motion in a standing wave
antinode
Portion of standing wave with maximum vertical motion.
wave refraction
Most waves approach land obliquely (not parallel to shore). End of wave closest to land slows first, causing wave to bend toward parallelism w/shore.
seiches
Standing waves that occur in natural basins. The oscillation of the surface is called seiching.
wave reflection
If wave strikes breakwall or steep beach, can reflect back. Angles same as light reflection. Creates chop.
swash
Water rushing up beach in direction of wave arrival.
backwash
Water flowing back down beach slope to sea.
longshore drift/current
caused by swash and backwash. Creates Zig-zag motion of water & sediment along beach. Sand grains move along beach which creates the beach itself. NET transport along beach. Avg. drift ~5-10 m/day depending on wave energy.
rip currents
Concentrated areas of backflow into sea. Often channeled by low in offshore bar. Undertow up to 1 m/sec. Get caught in this swim parallel to shore to allude concentrated pull.
internal waves
Waves can occur along any surface separating two mediums of different density (eg- air/water). Can get waves along top of pycnocline- can have large height, but move slowly and break, mixing the 2 layers
