Geography and Oceanography - Chapter 18 pdf

Internal WavesSlower speeds than surface waves because the density difference between water masses is less than between air and water... Standing WavesSeas, swell, and surf are progre

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

Sudden shifting of the ocean floor

due to earthquakes, volcanic

eruptions, and submarine slumping.

wavelengths (>100 km), and long periods 400-500 mph!!!

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

Driscoll et al., Geology, 28(5):407-410

North Carolina Example

Back to Wind-Driven Scenarios:

Storm Surges

extremely high water levels due to

persistent onshore winds rise in sea level

Hurricanes! (W Atlantic)

Cyclones! (W Pacific)

NASA Advanced Microwave Scanning Radar

Hurricane Katrina, Saturday, Aug 27, 2005

NASA PPT Radar, Visible Infrared Scanner, Tropical Microwave Imager

New Orleans, Wednesday, Aug 31, 2005

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

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

one another.

large heights.

Advection Along Internal Waves

Standing Waves

Seas, swell, and surf are progressive

waves

Standing waves (seiches)…

i.e., a fixed point.

which causes water to pile up at one

end of a basin.

Node = Fixed Point Antinode = maximum displacement

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!

(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.