Next Midterm Monday, May 18, 2009, 1:00 Here in Gilfillan Auditorium, closed book Same format as Test 1 Bring #2 pencil Study Guide NOW POSTED on class web site

Transformation of Wind-Driven Deep-water Waves (Figure 7-7a)

Transformation of Wind-Driven Shallow-water Waves (Figure 7-7b)

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 Massive 9.3 EQ. 30-ft vertical displacement, 60-ft horizontal displacement. “This tsunami is the first for which there are high-quality worldwide tide-gauge measurements and for which there are multiple-satellite altimetry passes of tsunami wave height in the open ocean.” Combined with numerical model simulations to show global reach of initial event. Mid-ocean ridges help to guide the tsunami energy propagation, which means they were still super long wavelength and hence super deep. 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 Oregon Coastal Atlas Tsunami Hazard Information http://www.coastalatlas.net or http://bit.ly/FG8rz

Figure 7-13a

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

L Hurricane Katrina, Sunday, Aug 28, 2005 Accumulation of water driven shoreward by storm winds: Elevated sea level at shore L Blue is 0.25 inches of rain per hour, green = 0.5, yellow = 1.0, red = 2.0 low atmospheric pressure accumulation of water driven shoreward by storm winds Water is deeper at the shore area, allowing waves to progress farther inland. 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.

Figure 5-17

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 (Figure 7-11)

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.