Today’s Tune
“This is the Sea”
by The Waterboys
Next Midterm
Monday, May 16, 2011, 1:00
 Here
in Gilfillan Auditorium, closed book
 Same format as Test 1
 Bring #2 pencil
 Study Guide POSTED on main class web
site:
http://dusk.geo.orst.edu/oceans/103syl.html
Transformation of Wind-Driven
Deep-water Waves
Transformation of Wind-Driven
Shallow-water Waves
Photography by Clark Little
Photography by Clark Little
Photography by Clark Little
Photography by Clark Little
Photography by Clark Little
Photography by Clark Little
Photography by Clark Little
Photography by Clark Little
Photography by Clark Little
Tsunamis
 Sudden
shifting of the ocean floor
due to earthquakes, volcanic
eruptions, and submarine slumping.
– open ocean: short heights, long
wavelengths (>100 km), and long periods
-- 400-500 mph!!!
– shallow water: their length shortens and
their height increases dramatically.
Global Wave Propagation After
2004 Sumatra Event
Titov, V., A.B. Rabinovich, H.O. Mojfeld, R.E. Thomson, and F.I. Gonzalez, The global reach of the 26 December 2004 Sumatra tsunami, Science, 309 (5743), 2045-2048, 2005.
Oregon Coastal Atlas
Tsunami Hazard Information
http://www.coastalatlas.net
or
http://bit.ly/FG8rz
Tsunami from slumping
North Carolina Example
Driscoll et al., Geology, 28(5):407-410
Back to Wind-Driven Scenarios:
Storm Surges
 extremely
high water levels due to
– Low pressure system - big storms
persistent onshore winds
rise in sea level
Hurricanes! (W. Atlantic)
Cyclones! (W. Pacific)
Hurricane Katrina, Saturday, Aug 27, 2005
NASA Advanced Microwave Scanning Radar
Hurricane Katrina, Sunday, Aug 28, 2005
Accumulation of water driven shoreward by storm winds:
Elevated sea level at shore
L
NASA PPT Radar, Visible Infrared Scanner, Tropical Microwave Imager
GOES satellite
New Orleans, Wednesday, Aug 31, 2005
ESRI.com
OSU Wave Tank
Back to 1998 El Niño
“The Perfect Storm”
Condition Black in Hawaii
Other Types of Progressive Waves
 There
is one other notable type of
progressive waves.
– Internal waves which occur underwater
and move along pycnoclines.
Internal Waves
 Slower
speeds than surface waves
because the density difference
between water masses is less than
between air and water.
– They occur when water masses slip over
one another.
– They have very long periods and very
large heights.
Advection Along Internal Waves
Standing Waves
 Seas,
swell, and surf are progressive
waves.
 Standing waves (seiches)…
– Oscillate back and forth about a node
i.e., a fixed point.
– Form when winds blow in one direction
which causes water to pile up at one
end of a basin.
Node = Fixed Point
Antinode = maximum displacement
Summary
Waves are disturbances that are generated on
or beneath the sea surface. Progressive waves
move along the sea surface.
 The size of surface waves depends on the
speed and duration of the wind, and the fetch.
 Waves affect water to a depth equal to or less
than one-half their wavelength.
 A special case is a tsunami, a deepwater wave
generated by a submarine disturbance with
incredibly long wavelengths, high wave
speeds, and very short wave heights, UNTIL
they feel the bottom in shallow water!

Summary
(Cont.)
 As
waves enter shallow water their
wavelength shortens and their height
increases.
 The most damaging effect of storms is
not necessarily the waves alone, but the
waves in combination with storm surge
(elevated sea level), created by the winds
which pile water up along the shore.