e wall of water that can
reach up to 1500 feet high! They come in sets. Tsunamis are incorrectly
named tidal waves. Tidal waves are caused by extremely strong winds and
tsunamis are caused by other things.
Tsunami means “harbor wave” in Japanese
Tsunamis are one of the deadliest natural disasters. They can wipe out
large numbers of people.
An earthquake is one of the causes of tsunamis. So
are undersea landslides, volcanic eruptions, and rarley meteorites and
The earthquakes that cause tsunamis are submarine earthquakes. That means
that they happen under water. An earthquake must rate above a 7.5 on the
Richter Scale to cause a tsunami.
The ground shoots up and displaces the
water. This causes the tsunami wave to form and move. As the wave
approaches land, it increases in size. When it reaches the land, it washes
over anything in its path. They are so strong they can knock down buildings
Tsunamis can do a lot things.
They cause floods, destruction, and deaths.
Tsunamis may also bring diseases like cholera. This can happen when dead
bodies that have not been buried decay. Many times more people die from the
diseases than the actual tsunami.
The deadliest tsunami occurred on December 26, 2004 and killed 150,000
people. It affected the countries of South East Asia.
They are as follows:
Indonesia, India, Bangladesh, Thailand, Sri Lanka, Malaysia, Kenya,
Sumatura, Maldives, Myanyar, and Somalia.
Tsunamis (pronounced tsoo-nah’-mee), or seismic sea waves, potentially the
most catastrophic of all ocean waves, are generated by tectonic
displacement–for example, volcanism, landslides, or earthquakes–of the
seafloor, which in turn cause a sudden displacement of the water above and
the formation of a small group of water waves having wavelength equal to
the water depth (up to several thousand meters) at the point of origin.
These waves can travel radially outward for thousands of kilometers while
retaining substantial energy. Their speed–characteristic of gravity waves
in shallow water and thus equal to the square root of gD, where g is the
gravitational constant and D is the depth–is generally about 500 km/h (300
mph), and their periods range from 5 to 60 minutes. In the open ocean their
amplitude is usually less than 1 m (3.3 ft); thus tsunamis often go
unnoticed by ships at sea.
In very shallow water, however, they undergo the
same type of increase in amplitude as swell approaching a beach. The
resultant waves can be devastating to low-lying coastal areas; the 37-m
(120-ft.) waves from the 1883 Krakatoa eruption, for example, killed 36,000
The characteristics of tsunamis as they approach shore are greatly affected
by wave refraction over the local bathymetry. Tsunami-producing earthquakes
usually exceed 6.5 on the Richter scale, and most tsunamis occur in the
Pacific Ocean because of the seismic activity around its perimeter.
tsunami warning system for the Pacific Ocean has been established; it
consists of strategically placed seismic stations and a communications
If within an evacuation zone, take the following actions:
picLOCAL EARTHQUAKE – May cause you to fall or have difficulty
standing. This is a natural tsunami warning. Initially, protect
yourself from earthquake effects. When the shaking stops, leave the
evacuation zones immediately.
picURGENT TSUNAMI WARNING – Possible tsunami generated by a
significant earthquake in local waters.
Sirens will sound. Turn on
radio. If an urgent tsunami warning for Oahu is announced, leave the
evacuation zones immediately.
picTSUNAMI WATCH – Significant distant earthquake has occurred.
Tsunami approach not confirmed but possible. No siren sounding.
Prepare for possible upgrade to tsunami warning.
picTSUNAMI WARNING – Tsunami approach confirmed. Sirens will sound.
Monitor radio. Be prepared to evacuate when advised/ordered by civil
picTSUNAMI EVACUATION – Sirens will sound.
Turn on radio. Those who
are in tsunami evacuation zones must begin evacuation when the
evacuation advisory/order is issued by civil defense (3 to 4 hours
prior to wave arrival). City busses will leave evacuation zones, and
roads will be sealed off by police no later than 45 minutes prior to
first wave arrival.
picIf you are in a steel and/or concrete building of six or more
stories move to the third floor or above and remain there until the
“All Clear” is announced. .