GEO 130 SPRING 2006
FILM STUDY GUIDE
Title: Tsunami: The wave that shook the world. NOVA, PBS, WGBH, Boston
Synopsis: On December 24, 2004 one of the strongest earthquakes ever
measured occurred for the coast of Indonesia. Because of the character of
this earthquake one of the deadliest natural disasters in modern history
soon followed. The film documents the causes and effects of this tsunami.
More Information:
http://en.wikipedia.org/wiki/2004_Indian_Ocean_earthquake
Definition:
The term tsunami is from the Japanese language meaning harbour ("tsu", 津)
and wave ("nami", 波 or 浪). . The term was created by fishermen who
returned to port to find the area surrounding the harbor devastated,
although they had not been aware of any wave in the open water. Tsunamis
are often and erroneously called “tidal waves”. They have nothing to do with
tides.
Major Concepts and additional information:
1. Earth’s crust is divided into plates which are moving powered by
convection currents in the mantle.
2. Where the plates make contact and grind together earthquakes occur.
3. The earthquake of 24Dec2004 occurred where a oceaninc plate (India
Plate) was subducted under a continental plate (Burma plate). The
hypocenter was at 3.316°N, 95.854°E, 30km below mean sea level.
4. Since the film was completed the quake is thought to have been of
magnitude 9.15 on the MOMENT MAGNITUDE SCALE.
5. A seismogram is a graph of the earthquake as detected by a
seismograph.
6. An increase of 1 unit means an increase of energy 31.6 times, 2 units
mean a 1000 times increase in energy.
7. The location of this quake was fairly shallow, near the sea floor. The
energy of a deep quake (hunderds of kilometers below the sea floor)
would be effectively dissipated within the solid earth.
8. A shallow quake like this one (30 km below mean sea level) transfers a
great deal of energy to the water above. This quake had a great deal
of motion upward and solid rock transferred energy to the water.
9. There is no tsunami warning center in for the Indian Ocean. The
Pacific Tsunami Warning Center of NOAA can warn for Pacific Ocean
tsunamis.
10. Tsunamis are detected by pressure sensors anchored to the sea floor.
An increase of depth above the sensor means the water above the
sensor weighs more therefore there is grater pressure.
11. The pressure information is transmitted to an anchored buoy above
then to a satellite then to the tsunami warning center.
12. A tsunami is generated because the energy of the earthquake must be
dissipated.
13. Most of the energy is dissipated in Earth’s crust.
14. When a great deal of energy is dissipated in the ocean TSUNAMI
INITIATION can occur when the water immediately above the
disturbance is lifted.
15. Billions of tons of water were displaced upward then split and
collapsed. This is the DISPERSIVE STAGE and the wave radiates
outward.
16. The most recent estimates put the death toll as more than 283,100.
The death that occurred farthest from the hypocenter happened
8,000 miles away in South Africa.
17. In the open ocean the tsunami was virtually undetectable. It becomes
a frightening surge of water near shore as the water become shallow.
18. In the open ocean a tsunami wave is a small hump travelling between
300 and 600 mph. Note: water is not moving en masse but it is energy
that is being transferred.
19. As the energy surge nears shore it slows dramatically but because the
leading edge is climbing up hill towards land and because of friction
with the bottom it slows faster than the trailing edge of the energy
surge.
20. AMPIFICATION occurs as the wave builds because the water farther
from shore, moving faster runs over top of the near shore water. As
the wave builds water near shore is drawn out to sea leaving a wide
area formerly underwater dry.
21. Many are lured to their deaths by this startling event.
22. The morphology of a coastline can mean a minor occurrence or a huge
wave. In some places the tsunami barely came ashore in others near by
the wave was 100 feet deep.
23. There are 5 causes of tsunamis: earthquakes, volcanoes, landslides
into the sea, landslides under the sea and asteroids. A major asteroid
impact would generate a tsunami of unimaginable size across the
entire planet.
24. The 24Dec2004 earthquake was one of the strongest earthquakes
ever. The strongest are (preliminary for 26Dec2004):
9.5
9.2
9.15
9.0
9.0
8.8
Chile, May 22, 1960
Prince William Sound, Alaska, March 28, 1964
Off the coast of Sumatra, Indonesia, December 26,
Andreanof Islands, Aleutian Islands, Pacific, March 9, 1957
Kamchatka, Russia, November 4, 1952
Off the coast of Ecuador, January 31, 1906
25. Earth’s day was shortened by 3 millionths of a second.
26. In the Canary Islands some scientists think the volcano La Palma may
collapse into the sea creating a large tsunami. The chance is though to
be slight
27. Off the coast of Oregon along the Cascadia Subduction Zone a
major earthquake could occur generating a large tsunami.