A presentation on Tsunami

1. Social Science project on

2. Contents
Project Overview
Intro..
Causes
Earthquake-Generated Tsunami
Characteristics
Drawback
2004 Indian Ocean Tsunami
Conclusion
Bibliography

3. Project Overview
The aim of this presentation is to study about
tsunamis waves . How are they caused , their
characteristics and their impact. Through studying all
these we can learn about tsunami waves. As the
destruction due to these waves can’t be stopped but it
can be reduced to save the precious lives.

4. Intro..
 The term tsunami comes from the Japanese,
meaning “harbor" (tsu) and “wave" (nami). Tsunami are
sometimes referred to as tidal waves. In recent years,
this term has fallen out of favor, especially in the
scientific community, because tsunami actually have
nothing to do with tides. Tsunami and tides both
produce waves of water that move inland, but in the
case of tsunami the inland movement of water is much
greater and lasts for a longer period, giving the
impression of an incredibly high tide.

5. Causes
 Although most tsunamis are generated by
underwater earthquakes, a tsunami can be generated
when convergent or destructive plate boundaries
abruptly move and vertically displace the overlying
water. It is very unlikely that they can form at divergent
(constructive) or conservative plate boundaries. This is
because constructive or conservative boundaries do not
generally disturb the vertical displacement of the water
column. Subduction zone related earthquakes generate
the majority of tsunami.

6.  Tsunamis have a small
amplitude (wave height) offshore,
and a very long wavelength (often
hundreds of kilometers long),
which is why they generally pass
unnoticed at sea, forming only a
slight swell usually about
300 millimetres (12 in) above the
normal sea surface. They grow in
height when they reach shallower
water, in a wave shoaling process.
A tsunami can occur in any tidal
state and even at low tide can still
inundate coastal areas.

7.  Most tsunamis are caused by
submarine earthquakes which
dislocate the oceanic crust, pushing
water upwards.
 Tsunami can also be generated by
erupting submarine volcanoes ejecting
magma into the ocean.
 A gas bubble erupting in a deep
part of the ocean can also trigger a
tsunami.

8. Earthquake-Generated
Tsunami
 An earthquake may generate a tsunami if the
quake:
• occurs just below a body of water,
• is of moderate or high magnitude, and
• displaces a large-enough volume of water.

9.  Drawing of tectonic plate boundary
before earthquake.
 Overriding plate bulges under strain,
causing tectonic uplift.
 Plate slips, causing subsidence and
releasing energy into water.
 The energy released produces
tsunami waves.

10. Characteristics
 When the wave enters shallow water, it slows down
and its amplitude (height) increases. The wave further
slows and amplifies as it hits land. Only the largest waves
crest.
 As the tsunami approaches the coast and the waters
become shallow , wave shoaling compresses the wave
and its velocity slows below 50 miles per hour. Its
wavelength diminishes to less than 12 miles and its
amplitude grows enormously , producing a distinctively
visible wave. Since the wave still has such a long
wavelength , the tsunami may take minutes to reach full
height .

11.  When the tsunami's wave peak reaches the
shore, the resulting temporary rise in sea level is
termed run up. Run up is measured in meters
above a reference sea level. A large tsunami may
feature multiple waves arriving over a period of
hours, with significant time between the wave
crests. The first wave to reach the shore may not
have the highest run up.
 About 80% of tsunamis occur in the Pacific
Ocean, but are possible wherever there are large
bodies of water, including lakes. They may be
caused by landslides, volcanic explosions, bolides
and seismic activity.

12. Drawback
 If the first part of a tsunami to reach land is a trough—
called a drawback—rather than a wave crest, the water
along the shoreline recedes dramatically, exposing
normally submerged areas.
 A drawback occurs because the tectonic plate on one
side of the fault sinks suddenly during the earthquake,
causing the overlaying water to propagate outwards with
the trough of the wave at its front. This is also why that
there would not be any drawback when the tsunami
travelling on the other side arrives ashore, as the tectonic
plate is "raised" on that side of the fault line.

13.  Drawback begins before the wave arrives at an
interval equal to half of the wave's period. If the slope
of the coastal seabed is small, drawback can exceed
hundreds of meters. People unaware of the danger
sometimes remain near the shore to satisfy their
curiosity or to collect fish from the exposed seabed.
During the Indian Ocean tsunami, the sea withdrew
and many people went onto the exposed sea bed to
investigate.

14. 2004 Indian Ocean Tsunami The 2004 Indian Ocean tsunami killed over 200,000
people with many bodies either being lost to the sea or
unidentified.
 According to an article in Geographical magazine
(April 2008), the Indian Ocean tsunami of December 26,
2004 was not the worst that the region could expect.
Professor Costas Synolakis of the Tsunami Research
Center at the University of Southern California co-
authored a paper in Geophysical Journal International
which suggests that a future tsunami in the Indian Ocean
basin could affect locations such as Madagascar,
Singapore, Somalia, Western Australia.

16. Conclusion
 In conclusion, I would like to tell tsunamis can be
very dangerous and deadly. As we do not have the
power to control or predict and detect tsunamis
because they are under water waves they become even
more dangerous and deadly and make them even more
difficult to escape. Tsunamis can damage a lot of
property and life and usually leave a panic for the
human basic necessities. So they are not a thing to be
taken lightly.

17. Bibliography
 I would like to mention some sources which proved
to be helpful in making this presentation. Some of
them are as follows :
i. www.google.com
ii. www.wikipedia.com
iii. The Times Of India (newspaper)
iv. Google Images