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Oceanography Exam 2
Waves
25
Science
Undergraduate 1
10/26/2011

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Term
What is the disturbing and restoring force of wind waves?
Definition
Disturbing force(energy input): Wind  wind waves
Landslide/faulting  tsunami
Moon/sun gravitation  tides
Rapid changes in atmospheric pressure  seiche
Restoring force: Gravity
Term
How do water particles move as a wave passes?
Definition
Term
What are wave orbitals?
Definition
Term
What defines a deep water wave?
Definition
Depth > L/2…waves do not ‘feel bottom’
Term
WHat defines a transitional wave?
Definition
L/2 > Depth > L/2…waves feel bottom
Term
What defines a shallow water wave?
Definition
Depth < L/20…waves ‘feel bottom’ strongly…ruled by bottom interaction
Term
What happens to a wave as it approaches the shoreline?( velocity, wave length, wave height, steepness and period)
Definition
Term
What is C=L/T
Definition
C= Wavespeed or Celerity
L= Wavelength(m)
T= Time/period(sec)
Term
What happens when a wave breaks?
Definition
Become shallow water waves,
‘Feel’ the bottom more and more strongly
Slow down due to bottom friction: Speed… so L  (T always constant)
Waves become closer together
Height increases…..Steepen until they Break
Waves crowd together, steepen until unstable
Spills forward because back outruns front
Transfer energy to land (pounding)
Breaks when L/H = 7, wave spills over
Term
3 types of surf: Spillers
Where do you find them?
Definition
low slope beach
-Waves build more slowly
-Collapses and spills down front
-More gradual energy loss
Constructive- carry sand onto the beach
Term
3 types of surf: Plungers
Where do you find them?
Definition
medium slope beach
-Waves steepen quickly
-Crest outruns trough
-Curls (good surfing wave!)
Term
3 types of surf: Surgers
Where do you find them?
Definition
high slope beach
-Wave breaks near beach…not good for surfing
-Sudden energy loss
-Destructive - backwash carries sand off the beach
Term
What are the possible causes of a tsunami?
Definition
When water in a lake or sea is displaced by:
- underwater fault movement
- landslide
- volcanic eruption
- large meteorite impacts
Term
What are the warning signs of a tsunami?
Definition
water level drops, smaller waves arrive first
Term
What prevention/ protection measures can be taken to minimize damage of a tsunami?
Definition
Build streets perpendicular to coast
Dig trenches and plant vegetation
Preserve coastal dunes, vegetation, coral reefs
Tsunami Warning Systems: Bottom Pressure Recorder (BPR) with transmitter
resolution of about 0.25 mm of water height change
Term
Main feautures of Dec 26 2004 tsunami?
Definition
EPICENTER: West of Java
HYPOCENTER: 30 km below sea level
-Magnitude 9.0 Strongest in 40 years,
-85 strong to moderate aftershocks
Burma (or Andaman) Plate – Indian Ocean Plate Boundary
Term
Main features of March 11 2011 tsunami?
Definition
EPICENTER: near Tohoku earthquake in northern Honshu, Japan
HYPOCENTER: ~32 km below sea level
-Magnitude 9.0
-Japan experienced over 900 aftershocks since the earthquake
Term
Where do tsunami typically occur?
Definition
At subduction zones
Term
How fast does a tsunami travel?
Definition
In open ocean up to 500mph
Near shore 20 mph
Term
How do water particles move as a wave passes?
Definition
They move in circular orbits
Term
What happens to a wave as it approaches the shoreline?
Definition
-Wavelength decreases
-Height increases
-Steepens until it breaks
-period is constant
Term
What is wave refraction?
Definition
Refraction is the bending of waves because of varying water depths underneath. The part of a wave in shallow water moves slower than the part of a wave in deeper water. So when the depth under a wave crest varies along the crest, the wave bends.

Focuses energy on headlands- causes erosion
Term
What is wave diffraction?
Definition
The apparent bending of waves around small obstacles or the spreading out of waves past small openings
Waves can enter ‘protected harbors’
Term
What is a seiche?
Definition
a standing wave in an enclosed or partially enclosed body of water.
Non progressive waves
due to quick atmospheric pressure change
Term
What is a rogue wave?
Definition
A huge, unexpected wave that comes out of nowhere. Usually caused by constructive intereferance.
1935 US Rampano- 34 meters or 112 feet high
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