Cataclysms And Catastrophes: Tsunamis

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Cataclysms And Catastrophes Tsunamis!
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Vista TopicTsunamis Walls of Water
Vista Overview A tsunami is a series of water
waves generated by a disturbance in the ocean.
Compared to other water waves, tsunamis have long
wavelengths and long periods which gives tsunamis
waves greater amplitude and energy than other
water waves.
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BackgroundTsunamis Generation

• Tsunamis sources displace the water column in the
  ocean
• Gravity then acts to restore displaced water
• A wave is generated that travels as an expanding
  ring across the oceans surface

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Tsunamis Wave Propagation
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PNG Tsunami- Sissano Lagoon
Source www.usc.edu/dept/tsunamis/PNG/sissano.html
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Asian Tsunamis- 12/26/04
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Asian Tsunamis- 12/26/04. Tourists flee a beach
in Thailand. Source The New York Times
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Learning Activities

• Understanding tsunamis and their sources with
  focus on asteroid impacts.
• Using wave energy, velocity, and height to
  demonstrate tsunami wave characteristics
• Tsunami prediction and creating a tsunami hazard
  map

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Activity 1Tsunamis Sources

• Earthquakes account for about 90 of all tsunamis
• Landslides
• Volcanic eruptions
• Escaping gas hydrates
• Impacts such as asteroids and ice berg chunks

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The Seismogenic Zone One Example
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IRIS Seismic Monitor
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Source Figure provided by Seth Stein, Professor,
Department of Geological Sciences, Northwestern
University, Evanston, IL 60208
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Impact Sources
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Activity 2Wave Characteristics

• A tsunami wave is a shallow-water wave
• Water depth affects speed and amplitude of the
  wave
• Energy remains nearly constant

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Wave Calculations

• Velocity v (g d)1/2
• Amplitude As/Ad (Vd/Vs)1/2

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Tsunami Wave Trough
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Activity 3Tsunami Prediction and Hazard Map

• Overview of the warning systems like WCATWC
• Use of tide gauges
• Use of seismometers
• Map the hazard zone of a costal area for a
  particular tsunamis event

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Can tsunamis occur close to home?
Source http//www.whoi.edu/home/index_pr_tsunami.
html (Illustration by Jack Cook, Woods Hole
Oceanographic Institution)
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Source http//www.whoi.edu/home/index_pr_tsunami.
html