Lecture 14:  Tsunami/Review for Exam 2
Focus Question:  Why do Tsunamis travel so fast and why are they so destructive?
ch 10, pgs 284-296 (pgs. 247-256)
This is a text version of the notes presented in class.

Feel free to email the instructor (knamjesn@kent.edu) with any
comments about the format and ease of use of these online notes.

1. Tsunami
- What is a Tsunami?
- Why are they so Destructive?

2. What is a Tsunami?
Tsu = harbor
Nami = wave
- not confined to harbors
- not created by tides
Created by direct displacements of the water's surface via undersea earthquakes,
  landslides or volcanic activity
Energy travels outward (like ripples that spread when a rock is thrown into a pond)

3. Aleutian Trench Tsunami - April 1946
- Caused by an earthquake that displaced the sea floor
- Significant damage in the Aleutians and Hawaii
Graphic: Garrison, Fig.10.28, pg. 286 (Fig. 10.30, pg. 248)

4. Tsunami Propagation
Tsunami radiate away from where they are created
As they travel, they can bend and their speed can change due to the shape of the basin
they are shallow water waves, and so touch the ocean bottom wherever they are
Graphic: Garrison, Fig. 10.29, pg. 287 (Fig. 10.31, pg 249).

5. Tsunami Approaching the Shore
Tsunami move very fast in the deep ocean  (~200 m/s or ~500 mph)
They have extremely long wavelengths, and speed = wavelength/period, so speed is strongly influenced by very long wavelength waves.
They steepen and grow to large heights as they approach shallower coastal regions

6. Tsunami Ashore
Tsunami wash ashore as a series of waves
- Crests and troughs are usually separated by ~15 minute intervals
- The trough can arrive before the crest
Onshore, tsunami usually appear as a very rapidly moving, very high tide (rather than a
curling breaker)
Wave heights at the shore can be 30 meters (or larger)
Graphic: Garrison, Fig. 10.32, pg. 289 (pg. 250).

7. The Force of the Wave
Tsunami are capable of intense damage and loss of life
Coastline geometry and distance from the triggering event determine the height of a tsunami

8. The Tsunami Warning System
Objective = predict the intensity and time of arrival of tsunami generated by earthquakes
Anchored instruments measure sea level changes as tsunami pass over
Warnings and watches issued based on predicted arrival times

9. Tsunami and the Pacific
Common in the Pacific due to seismic activity at subduction zones
Travel times calculated based on the time of the triggering event
Tsunami can reflect off land masses - the reflection can result in an area being affected by the same tsunami twice!

Exam 2 on Wednesday, October  17th
Covering Lectures 8-14 (Ocean Structure through today’s lecture)
Style:  Multiple Choice & Matching
Number of Questions:  Between 45 and 50
 Approximately 95% from lecture material
 Approximately 5% from readings not covered in lecture

How much does this count?  Each of your best 2 exam scores (best 2 of 3) will count towards 30% of your final grade.
You will need to turn in both your scantron answer sheet AND your test to get credit on the exam.
BRING A PENCIL AND AN ERASER!