Announcements

• Exams are looking pretty good -- ridiculously close to a classic bell-shaped curve -- some A’s, more B’s, lots of C’s, fewer D’s, no F’s yet (I don’t think)…

• Today/Weds/after break we’ll do tsunami; I wouldn’t come to class on Friday if I were you…

TSUNAMI

• READ– p. 226 - 229 (up to “Variation along a Coastline”,

including Case Study 8.1)– p. 235 - 240 (including Case Study 8.2 and the

survivor story)– p. 242 (paragraph that begins with “Tsunamis…”)– p. 247-248 (section on tsunami)– p. 262 (“Adjustments to Tsunamis”)

TSUNAMI

• The volcano chapter was back-up for me talking about my field of expertise -- now we’re into things I know less about -- so count on quizzes/clicker Q’s to show you’ve read

Review (= clickers, of course)

Cerro Negro, an odd cinder(?) cone in Nicaragua, last erupted last in 1999. In 2004, there was active seismicity at Cerro Negro. Using what you know

about cinder cones, would you say this one is

• dormant

• extinct

• activeCerro Negro, Nicaragua

My favorite dome erupted 110,000 years ago and 70,000 years ago. Using what you know about domes, would you say

my dome is

• dormant

• extinct

• active

(Mt. Elden -- not my favorite, but very cool, nonetheless)

The San Francisco Volcanic Field has been erupting for 8 million years, on and

off. The most recent eruption was Sunset Crater, ~ 900 years ago. The SFVF is

best characterized as…

1. dormant

2. extinct

3. active

context

• We learned from the 2004 Banda Aceh earthquake and tsunami that many parts of the world aren’t well prepared for tsunami. Things are radically better already in the SW Pacific

• We’ll look at a “first-world” country and see how they’re preparing, but first you need to know about tsunami in general

The science

To understand tsunami you have to understand waves…

• Sea or lake (“normal”) waves– velocity of wind– duration of wind– fetch

• (Read about wave sets and rogue waves in the text)

Wave terms1. Crest/trough2. L = wavelength3. H = wave height4. T = wave period5. V = wavelength/

wave period6. wave base = ~

1/2 L

How “normal” waves workquack

Why do waves break?

Tsunami waves are different…

WIND-GENERATED TSUNAMI

periods of 5-20 seconds

periods of 10 minutes - 2 hours

wavelengths of 10 - 200 meters

wavelengths of 100 - 500 meters

velocities of <50 km/h (= ~30 mph)

velocities of >800 km/h (= ~500 mph)

Tsunami waves don’t “break” as they near shore