4. Know what these terms mean!
Crest
Trough
Wavelength
Wave Height
Amplitude
Period
5. Wave Motion and Wave Speed
How do particles move through waves?
Orbit is created where particles move up and down or
forward and backward
How different below the surface?
Less energy
7. Deep-Water Waves
How is a deep water wave classified?
Water must be deeper than half of the wave length
Storm center waves move outward
Middle of storm center is a mixture of wave heights,
lengths and periods
Long waves leave storm center and move faster than
most waves = Dispersion
Waves that group together = wave trains
8. Wave Interaction
What happened during “The Perfect Storm”?
Constructive Interference or amplification
Waves can pass through, amplify, or cancel each
other out
Also can come at angles to each other
Wave trains can synchronize, crest and create smaller
waves
http://www.youtube.com/watch?v=dpZLGbvIzx0
10. Wave Speed
Waves speed = celerity
S = wavelength/wave period or C = L/T
Remember length is distance and period is time!
11. Wave Height
What affects wave height?
Wind speed, duration and fetch
Fetch = distance over the water that wind blows to
create waves moving in the same direction
All three variables must combine to make BIG
WAVES
12. The Beaufort Scale source:
http://www.aoml.noaa.gov/hrd/tcfaq/D10.html
Relate height and period to speed, duration and fetch
= Beaufort Scale of sea state
13. Wave Steepness
How is steepness measured on a wave?
Steepness = Height/Length
How do waves behave differently in shallow water?
Water orbits compress and forward speed of wave reduced
Shallow water wave is wave that enters depth 1/20th
of wave
length
Wave crests bend as approach shore due to difference of
speed between ends of wave crests (i.e. shallow end slow
and deep end fast) = refract
16. Diffraction is when a wave travels toward a barrier
and through a small opening = waves radiate outward
Important information for the design of harbors and
safe mooring
Remember Polynesians used wave patterns to travel
and locate other islands
Length and speed controlled by depth
17.
18. The Surf Zone
What affects how waves behave in the surf zone?
Depth of water and shape of shoreline
Look for the three different shore line examples in
your book
Narrow steep sloped beaches produce bigger waves
for surfers!
19. The Music of Surfing
http://www.youtube.com/watch?v=urtbRmPuLpk
http://www.youtube.com/watch?v=fP1QK0XCt1U
http://video.tiscali.it/canali/truveo/1673452417.html
20. Tsunamis
What produces tsunamis wave?
Earthquakes or sudden movement of earth’s crust
Results in extremely long waves (54-108 miles long)
At point of origin boat may not feel full force (3-6 ft
swell)
When path of wave blocked by coast or island the
height builds rapidly
Leading edge may be a trough or crest
22. What is the driving force
behind tides?
Mainly the gravitational pull of the moon
Three types of tides:
Diurnal = one high and one low
Semi-diurnal = high and low twice a day
Mixed = high at different heights and low
different heights
27. What are the main forces that
come into play?
Earth and moon and centrifugal force
Earth’s water covering is malleable and pulls or
bulges toward the gravitational pull of the moon. As
the moon moves position so to follows the tidal bulge
At the same time the centrifugal force acting on the
Earth pulls opposite the moon producing two bulges
at opposite ends and two troughs in between
30. What is a flood tide and what
is an ebb tide?
Flood is a rising tide and ebb tide is a falling tide
Low Tide = lowest height reached during the
tidal cycle
High Tide = greatest height reached during that
tidal cycle
Minus Tide falls below the mean value
31. Tidal Day
The point at which the tidal cycle begins is 50
minutes later each day due to the interplay of the
earth and moon’s orbits
Therefore, a tidal day or cycle is 24hrs and 50 minutes
32. Spring Tides and Neap Tides
When do spring and neap tides occur?
Spring Tides occur when the moon and sun are on
the same side of the earth creating more pull or bulge
and thus higher tides than normal
Neap Tides occur when the moon is in it’s first
quarter and it is located at right angles to the earth
and sun
33. Diurnal Tides
When the moon or sun N. or S. of equator one bulge
found in Northern and other in Southern Hemisphere
thus one high and one low tide
Sun moves from Tropic of Cancer to Tropic of
Capricorn each year and therefore more diurnal tides
during summer and winter solstices
34.
35. Are tides short or long waves from what you have learned thus
far?
Long waves that behave like shallow-water waves
Speed of approximately 200 m/sec
Tidal friction created between tidal currents and sea
floor
Tidal waves create tidal turbulence through out water
column and thus mixing nutrients from deeper levels
to upper levels of the column
Tidal waves reflect off of land masses and sometimes
become standing waves
36. Predicting Tides and Tidal Currents
How are tides predicted?
Water level stations at coastal locations that measure
tidal changes for several years
Primary tidal stations run for at least 19 years to
coincide with 18.6 period year of the moon
Mean tidal levels gathered from the data with
astronomical information
NOAA source of tide tables
Private companies have taken over the dissemination
of information
42. Energy from Waves and Tides
How can energy be harnessed from waves and
tides?
Changing water level to lift an object
Using orbital movement of water
Using rising water to compress air in a chamber
Power of all the waves in the ocean 3000 power
produced at Hoover dam
Scotland and Norway currently use wave power
to generate electricity
43. What is the cost of capturing the wave energy that usually shapes
coasts?
Energy from tides only in areas of high tidal range
Rance River in France and Annapolis River in Nova
Scotia
Expensive to produce compared to other sources of
power
New efforts underway in England, Scotland and
Norway
http://video.techrepublic.com.com/2422-13792_11-
193651.html
In the United States?
