Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
119 Cards in this Set
- Front
- Back
how do all ocean waves begin?
|
as disturbances caused by release of energy
|
|
what's the most significant cause of ocean waves?
|
wind
|
|
how do waves transmit energy through matter?
|
by oscillatory motion
|
|
what are 2 types of progressive waves?
|
longitudional and transverse (orbital is a combination of the 2)
|
|
what happens to circular orbital motion with depth?
|
it decreases
|
|
what happens at the wave base?
|
water motion ceases entirely
|
|
where is the wave base?
|
at 1/2 the wavelength
|
|
if water depth is greater than 1/2 the wavelength, the wave is known as a....
|
deep water wave
|
|
if water depth is less than 1/20 of wavelength, the wave is known as a....
|
shallow water wave
|
|
what is the wavelength range of transitional or intermediate waves?
|
2d < L < 20d
(d = depth, L = wavelength) |
|
the wavelength of capillary waves is less than what?
|
1.74 cm
|
|
the wavelength of gravity waves is greater than what?
|
1.74 cm
|
|
what is the dominant restoring force of capillary waves? gravity waves?
|
capillarity; gravity
|
|
what are 3 factors that influence the size of wind generated waves?
|
wind speed, duration (time), and fetch
|
|
what is a fully developed sea?
|
an equilibrium condition that is reached when the maximum wave height is achieved for a particular wind speed, duration, and fetch
|
|
what is swell?
|
uniform, symmetrical waves that transmit energy from the sea across the ocean
|
|
what are rogue waves caused by? aka superwaves
|
constructive interferene
|
|
when do waves release energy near the surf zone?
|
the steepness exceeds 1:7 ratio?
|
|
if the height of a wave is 7 m, what must the minimum wavelength be so the wave doesn't break?
|
49 m
|
|
what are spilling breakers?
|
waves that break on a relatively flat surface
|
|
which waves are best for surfing? why?
|
plunging breakers; 'cuz they have curling crests
|
|
what happens when swell approacehs the shore?
|
segments of the waves that first encounter shallow water are slowed, where as other parts unaffected by the shallow water move ahead, causing the wave to refract, or bend
|
|
why is refraction significant?
|
it concentrates wave energy on headlands
|
|
what is a standing wave?
|
an interference pattern caused by reflection of waves off seawalls or other barrier; crests do not move laterally as in progressive waves but alternate with troughs at antinodes
|
|
what happens between the nodes and antinodes of a standing wave?
|
there is no vertical water movement
|
|
how are tsunami, or seismic sea waves caused?
|
by sudden changes in the elevation of the sea floor, such as from fault movement or volcanic eruptions
|
|
tsunami often have lengths exceeding _____ meters
|
200
|
|
where do most tsunami occur?
|
in the pacific
|
|
why is The Pacific Tsunami Warning Center (PTWC) important?
|
it has dramatically reduced fatalities by successfully predicting tsunami using real time seismic information
|
|
True or False? In shallow-water waves, wave speed increases with increased water depth, while in deep-water waves, wave speed increases with increased wavelength.
|
True
|
|
True or False? In the ocean, a rogue wave is also known as "swell."
|
False
|
|
True or False? Internal waves are usually found in areas where there is a strong, permanent pycnocline.
|
True
|
|
True or False? Internal waves can sometimes exceed heights of 100 meters and can carry matter to great depths.
|
True
|
|
True or False? The superposition or overlapping of two waves always results in destructive interference between the different waves.
|
False
|
|
True or False? Waves always travel in the same direction as the prevailing current, even far offshore.
|
FAlse
|
|
True or False? When a tsunami reaches a coastal area, it is always represented by a single rapid surge of water toward the shore, resembling a suddenly-occurring high tide (which is why they are misnamed "tidal waves").
|
False
|
|
What is wave refraction?
|
the bending of waves as they approach a coastline
|
|
If a tsunami leaves the Hawaiian Islands travelling toward the west coast, how long will it take to arrive?
|
5 hours
|
|
these waves are also known as push pull waves
|
longitudinal
|
|
what type of a wave is sound?
|
longitudinal
|
|
True or False: energy can be transmitted through all states of matter (solid, liquid, gas) by longitudinal movement of particles
|
True
|
|
these waves are aka side to side waves
|
transverse
|
|
tying one end of a rope to a doorknob while the other end is moved up and down or side to side is example of this type of wave motion...
|
transverse
|
|
what is the period of most wind generated waves?
|
0 sec - 5 minutes
|
|
what is the period of most tsunami?
|
5 min to 12 hrs
|
|
what is wave steepness?
|
waveheight/wavelength
|
|
what steepness ratio must be exceeded for a wave to break?
|
1:7
|
|
how is wave speed defined?
|
wavelength/period
|
|
what is the speed of a deep water wave, in m/s?
|
1.25 * sqrt(wavelength)
wavelength in m |
|
what is the speed of a deep water wave in m/s in terms of its period?
|
1.56 * Period
|
|
for deep water waves, the shorter the wavelength, the faster the wave travels?
|
false; (longer wavelength)
|
|
True or False: for a deep water wave, the wave speed depends ONLY on the wavelength
|
True
|
|
the wave speed in m/s of a shallow water wave in terms of the water depth, d, is.....
|
S = 3.13 * sqrt(d)
|
|
True or False: for shallow water waves, the deeper the water, the faster the wave travels
|
True
|
|
give 2 examples of shallow water waves
|
tides, tsunami
|
|
True False: for shallow water waves, the speed depends solely on water depth
|
true
|
|
True or False: for intermediate waves, the speed depends solely on wavelength
|
false; (wavelength and water depth, since they're INTERMEDIATE)
|
|
what are whitecaps?
|
open ocean breakers that form when steepness reaches a critical value of 1/7
|
|
a Beaufort number of __ would be classified as a hurricane
|
12
|
|
a Beaufort number between __ and __ would indicate a breeze
|
1-5
|
|
a Beaufort number between __ and ___ woudl indicate gale
|
6-9
|
|
a Beaufort number between __ and ___ woudl indicate a storm
|
10-11
|
|
what was the height of the largest authentically recorded wind generated wave?
|
34 m (112 feet), which contradicted the 60 ft rule
|
|
what is wave dispersion?
|
the sorting of waves by wavelength
|
|
what is the decay distance?
|
the distance over whcih waves change from a choppy "sea: to uniform swell, which can be up to several hundred kilometers
|
|
what are interference patterns? give 3 examples
|
when swells from different storms run together, the waves clash and interfere w/ one another; constructive, destructive, mixed
|
|
what is an example of a free wave?
|
swell
|
|
what is a free wave/
|
a wave moving with the momentum and energy imparted to it in the sea area but it is not experiencing a maintaining force that keeps it in motion
|
|
what is a forced wave?
|
it's maintained by a force that has a periodicity coninciding with the period of the wave
|
|
what are rogue waves?
|
massive, solitary waves that can reach enormous height and often occur at times when normal ocean wave are not unusually large
|
|
what is the probability of a rogue wave?
|
one/billion
|
|
in what conditions do rogue waves occur?
|
when storm driven waves move against strong ocean currents, causing the waves to steepen, shorten, and become larger
|
|
where do conditions for rogue waves occur?
|
along the SE coast of Africa, where the Agulhas current flow directly against large Antarctic storm waves, creating rogue waves
|
|
what was the worst disaster in the history of yachting?
|
the 1979 Fastnet Race, from the English Channel to Ireland and back
|
|
name 2 yachting disasters
|
2. Fastnet in 1979
1. Admiral's Cup Series races from Sydney to Hobart in 1998 |
|
what is the surf zone?
|
the zone of breaking waves
|
|
what do breaking waves indicate near the coast?
|
shallow water
|
|
what happens to the speed, wavelength, and wave height as a wave enters shoaling (shallow) water?
|
speed decreases, wavelength decreases, wave height increases (increase in steepness)
|
|
what is a handy way of estimating water depth in the surf zone?
|
the depth of water where waves are breaking is 4/3 times the breaker height
|
|
what causes a wave to topple over and break/
|
at the surface, individual water particles have not felt bottom, so the top part travel faster than the bottom part => top part overruns the bottom part and the wave breaks
|
|
these types of breakers are a result of gently sloping ocean bottom, which extracts energy from the wave more gradually, producing a turbulent mass of air and water that runs down the front slope of the wave instead of producing a spectacular cresting curl
|
spilling breaker
|
|
this type of breaker has a curling crest that moves over an air pocket; they form on moderately steep beach slopes; best for surfing
|
plunging breaker
|
|
this type of breaker occurs when the ocean bottom has an abrupt slope, and wave energy is compressed into a shorted sistance and the wave will surge forward; board surfers tend to avoid them
|
surging breaker
|
|
how is a surfer propelled forward by the wave's energy?
|
surfers balance the force of gravity, which is directed downward, with the buoyant force (perpendicular to the wave face)
|
|
why do all waves come in straight toward a beach despite their original orientation?
|
cuz of refraction
|
|
what do orthogonal lines indicate?
|
how energy is distributed along the shoreline by breaking waves
|
|
how are orthogonal lines different in headlands and bays?
|
they converge on headlands and diverge in bays
|
|
what is the surf zone?
|
the zone of breaking waves
|
|
what do breaking waves indicate near the coast?
|
shallow water
|
|
what happens to the speed, wavelength, and wave height as a wave enters shoaling (shallow) water?
|
speed decreases, wavelength decreases, wave height increases (increase in steepness)
|
|
what is a handy way of estimating water depth in the surf zone?
|
the depth of water where waves are breaking is 4/3 times the breaker height
|
|
what causes a wave to topple over and break/
|
at the surface, individual water particles have not felt bottom, so the top part travel faster than the bottom part => top part overruns the bottom part and the wave breaks
|
|
these types of breakers are a result of gently sloping ocean bottom, which extracts energy from the wave more gradually, producing a turbulent mass of air and water that runs down the front slope of the wave instead of producing a spectacular cresting curl
|
spilling breaker
|
|
this type of breaker has a curling crest that moves over an air pocket; they form on moderately steep beach slopes; best for surfing
|
plunging breaker
|
|
this type of breaker occurs when the ocean bottom has an abrupt slope, and wave energy is compressed into a shorted sistance and the wave will surge forward; board surfers tend to avoid them
|
surging breaker
|
|
how is a surfer propelled forward by the wave's energy?
|
surfers balance the force of gravity, which is directed downward, with the buoyant force (perpendicular to the wave face)
|
|
why do all waves come in straight toward a beach despite their original orientation?
|
cuz of refraction
|
|
what do orthogonal lines indicate?
|
how energy is distributed along the shoreline by breaking waves
|
|
how are orthogonal lines different in headlands and bays?
|
they converge on headlands and diverge in bays
|
|
how does diffraction result?
|
from wave energy being transferred around or behind barriers that impede a wave's forward motion
|
|
in wave reflction, the angle of incidence = _____ __ __________
|
the angle of reflection
|
|
an outstanding example of wave reflection occurs where?
|
in an area called "The Wedge" which develops west of the jetty that proects the harbor entrance at Newport Harbor, California
|
|
in "The Wedge", wave height often exceeds what? what types of breakers does it produce?
|
8 m; plunging breakers that are way 2 challenging for surfers
|
|
when are standing waves produced?
|
when waves are reflected at right angles to a barrier; they're the sum of 2 waves with the same wavelength moving on opposite directions, with no net movement
|
|
what are nodes?
|
lines along which there is no vertical movement?
|
|
what are antinodes?
|
crests that alternately become troughs, which are the points of greatest vertical movement within a standing wvae
|
|
how are most tsunamis caused?
|
by fault movement
|
|
do fault movements that produce horizontal or vertical displacements generate tsunami?
|
vertical, because it changes the volume of the ocean basin, and affects the entire water column; horizontal movement is side to side and does not change the water column volume and does not generate tsunami
|
|
how fast do tsunamis move?
|
more than 700 km/hr in open ocean
|
|
True or False: the first surge of a tsunami is always the largest
|
false
|
|
True or False: many small tsunami are generated each year and go largely unnoticed
|
true
|
|
on average, how many tsunamis occur each decade?
|
57
|
|
almost __% of all great wavesare generated in the pacific ocean
|
86
|
|
when was Krakatau?
|
Aug 27, 1883
|
|
how many were killed by the Krakatau explosion and subsequent tsunami?
|
36,000 (over 1000 villages drowned)
|
|
what was Hawaii's worst natural disaster?
|
a tsunami that hit Hilo on Apr 1, 1946: M_w = 7.3 earthquake in Aleutian Trench caused it; $25 million damage and 159 killed
|
|
list 3 nations that expereience more tsunami than any other place on earth, in order
|
1. Japan
2. Chile 3. Hawaii |
|
What is the record height of a tsunami?
|
Ryukyu Islands, South of Japan in 1971: normal sea level was raised by 85 m
|
|
what was the most deadly tsunami?
|
Aura, Japan, 1703: 100,000 deaths
|