Transcript tsunamis - MrDanielASBSukMSSci

Tsunamis
Learning Objectives:
- To develop your understanding of the term
Tsunami.
- To be able to identify the reason a tsunami
occurs and its affects.
The Origin of the Word
• The word “Tsunami” comes from the
Japanese word ‘tsu’ (meaning harbour)
and ‘nami’ (meaning wave).
• Tsunamis are common throughout
Japanese history, with 195 documented
events.
Tsunami: A series of waves created when a body of water (ex.
Ocean) is rapidly displaced from events such as, underwater
earthquakes, volcanic action, nuclear testing, landslides or even
asteroid impacts.
HOW A TSUNAMI IS CREATED
The displaced water then
moves away from the
Earthquake epicentre,
creating a large wave
that forms a tsunami
Tectonic plates converge
on plate boundaries, forcing
one plate upwards.
This causes an Earthquake,
and displaces LARGE
amounts of water.
Other Ways a Tsunami is
Formed
If an asteroid hits
an ocean, it could
cause a large
Tsunami.
Underwater volcano
eruption can cause a
A tsunami
A landslide that
deposits large
amounts of rock
into a body
of water could
cause a tsunami
What warning signs are
there to tell a person a
tsunami is going to hit the
coastline?
Tsunamis are difficult to detect out in the
ocean. The only warnings signs are, if
you can feel an earthquake or if you see
the draw back of the shoreline.
Why are Tsunamis difficult to detect out in the
Ocean?
THE BUILD UP OF THE WAVE:
1) Large amounts of water is displaced
2) The water moves away from point of origin
3) Initially the wave HEIGHT is SMALL, with a LARGE wave LENGTH
4) As the wave reaches a coast, the DRAWBACK slows the front of the wave, causing
the back to catch up.
5) This condenses the wave length and INCREASES the wave height dramatically.
How do coastlines affect the
height of the tsunami
The height of a tsunami is partially
dependent on the coastline. If the
coast has a gradual drop-off in the
water, the wave height will not be
forced to build up in height
dramatically, keeping a larger wave
length.
If the coastline has a steep drop-off
into the water, then the wave’s
height increases drastically. This is
due to the water under the wave
being forced upward as it hits the
shore
This image is of a
tsunami the struck
Thailand on 26th
Dec. 2004.
The Indian Ocean
Tsunami
This undersea mega thrust ___________ struck at 00:58:53
UTC (07:58:53 local time) in the Indian Ocean off the western
coast of northern Sumatra, __________. It was the largest
earthquake on Earth since ______, and tied for _______
largest since 1900. This earthquake cause a giant Tsunami,
that took over 200, 000 lives in __________ countries.
Indonesia
1964
eleven
earthquake
Epicentre of the
earthquake
fourth
The progress of the wave across the ocean
How BIG?
The earthquake was unusually large in
geographical extent. An estimated 1,200 km
(750 mi) of fault line slipped 20 m (60 ft) along
the subduction zone where the India Plate dives
under the Burma Plate. The seabed of the
Burma plate is estimated to have risen several
metres vertically up over the India plate, creating
shock waves in the Indian Ocean that travelled
at up to 800 km/h (500 mi/h), forming tsunamis
when they reached land.
• The epicentre of the earthquake was 155 miles from
Banda Aceh, off the west coast of northern Sumatra,
Indonesia
• Within hours had affected millions of people living
along coastlines facing the Indian ocean
• The graphics below show how high the wave was as it
arrived at different places around the Indian Ocean:
Satellite photographs of part of Banda Aceh, the nearest
large settlement in Indonesia to the epicentre of the
earthquake and the one most affected by the Tsunami in
terms of the amount of people who died
A street littered with
vehicles and other
debris near Patong
Beach in Phuket
http://youtube.com/watch?v=kGIz_-2UFJc&feature=related
Homework
• Visit this website…
http://www.fema.gov/kids/tsunami/