tsunami ppt for class 8

1. TSUNAMI

2. The devastating impact
of seismic sea waves

3. A tsunami from Japanese"harbor wave” English
pronunciation:, also known as a seismic sea wave, is a
series of waves in a water body caused by the displacement
of a large volume of water, generally in an ocean or a large
lake. Earthquakes, volcanic eruptions and other underwater
explosions (including detonations of underwater nuclear
devices), landslides, glacier calvings, meteorite impacts and
other disturbances above or below water all have the
potential to generate a tsunami Unlike normal ocean waves
which are generated by wind or tides which are generated by
the gravitational pull of the Moon and Sun, a tsunami is
generated by the displacement of water.

4. How do EQ cause tsunami?

5. Tsunami causes
Unless there is an underwater landslide, strike-slip EQ WILL
NOT cause tsunami
Most tsunami generated by subduction zones
 Chile,
 Alaska,
 Japan,
 Cascadia,
 Philippines,
 New Zealand

6. Tsunami wavelength
Long wavelengths (over 100 km)
Periods longer than 1 hour
316,800 ft = 60 miles

7. Tsunami wave speed
Travel at high speeds :
400 to 500 mph (~200 yards/sec)
 Alaska to CA 4 to 7 hrs
 Alaska to Hawaii 4 to 6
hrs
 Chile to Hawaii 14 to
15 hrs
 Chile to Japan 22 to 33
hrs

9. Tsunami Warning
When warning is issued – low
lying areas are evacuated
U.S. Coast guard issues warnings
over marine frequencies
Some places have sirens

10. Energy in tsunami
Waves can travel great distances and still be
very distructive
Loss of energy in a wave is inversely
proportional to λ
Since λ very long, little energy lost