What does Tidal Waves or
- A tidal wave is an unusually high
sea wave that follows an earthquake or
- They are the most destructive
waves in the ocean.
- Now they are called Tsunami
(pronounced soo-nam-ee) because they are
not caused by tides or even by the wind,
but by underwater earthquakes, landslides
or volcanic eruptions .
- The term "tidal wave"
is a misnomer; although a tsunami's
impact upon a coastline is dependent upon
the tidal level at the time a tsunami
strikes, tsunamis are unrelated to the
tides. Tides result from the imbalanced,
influences of the moon, sun, and planets.
Tsunami can also be caused by a
nonseismic event, such as a landslide or
- Tsunami is a Japanese word with
the English translation, "harbor
wave." Represented by two
characters, the top character,
"tsu," means harbor, while the
bottom character, "nami," means
- This monster
Tsunami is a chain of fast moving waves
caused by sudden trauma in the ocean.
They can be generated by earthquakes,
volcanic eruptions, or even the impact of
meteorites. They are most common around
the edge of the Pacific, where more than
half of the World's volcanoes are found.
These seismic surges can assault
coastlines, often with little or no
warning. Rocks weighing as much as 20
metric tons have been plucked from sea
walls and carried 180m inland. It speeds
across the sea as fast as a jet airplane.
On reaching land, it can suck all the
water out of a harbor. Then the creature
may grow more than 100 feet tall and
flatten whole villages. These
disturbances cause the sea bed to move
very quickly, which shifts a large amount
of water and disrupts the sea surface. A
train of waves is set in motion traveling
away from the source of
- Tsunamis are most often generated
by earthquake-induced movement of the
ocean floor. Landslides, volcanic
eruptions, and even meteorites can also
generate a tsunami.
- If a major earthquake is felt, a
tsunami could reach the beach in a few
minutes, even before a warning is issued.
Areas at greatest risk are less than 25
feet above sea level and within one mile
of the shoreline. Most deaths caused by a
tsunami are because of drowning.
Associated risks include flooding,
contamination of drinking water, fires
from ruptured tanks or gas lines, and the
loss of vital community infrastructure
(police, fire, and medical facilities).
- From an initial tsunami
generating source area, waves travel
outward in all directions much like the
ripples caused by throwing a rock into a
pond. As these waves approach coastal
areas, the time between successive wave
crests varies from 5 to 90 minutes. The
first wave is usually not the largest in
the series of waves, nor is it the most
- Furthermore, one coastal
community may experience no damaging
waves while another, not that far away,
may experience destructive deadly waves.
Depending on a number of factors, some
low-lying areas could experience severe
inland inundation of water and debris of
more than 1,000 feet. About four out five
tsunamis happen within the "Ring of
Fire," a zone of frequent
earthquakes and volcanic eruptions
roughly matching the borders of the
Pacific Ocean. Along the ring's edges,
giant slabs of the earth's crust, called
tectonic plates, grind together.
Sometimes the plates get stuck, and
pressure builds, causing the plates to
suddenly come apart and slam into a new
position. This jolt causes an earthquake.
If an earthquake lifts or drops part of
the ocean floor, the water above it
starts moving, too, triggering a tsunami.
- A tsunami is actually a series of
waves that can travel at speeds averaging
450 (and up to 600) miles per hour in the
open ocean. Oddly, in deep water its
waves are only a few feet high and would
not be felt by ships. This would also
make them unnoticeable from the air but
when the waves approach shore, they
increase in energy and height. Unusual
wave heights have been known to be over
100 feet high. However, waves that are 10
to 20 feet high can be very destructive
and cause many deaths or injuries. Often
before a tsunami hits, there is a giant
vacuum effect, and water is sucked from
harbors and beaches. People see the bare
sea bottom littered with flopping fish
and stranded boats. That is because waves
are made out of crests, or high points,
and troughs, or dips between crests. When
a trough hits land first, the water level
drops drastically. Usually another wave
blasts ashore about 15 minutes later,
then another and another, for two hours
- Tsunamis have killed more than
50,000 people in the past century. Twenty-four tsunamis have caused damage in the United States and its territories during the last 204 years. Just since 1946,
and caused a half billion dollars of property damage in Hawaii, Alaska, and the West Coast.
- As a tsunami nears the coastline, it may rise to several feet or, in rare cases, tens of feet, and can cause great loss of life and property damage when it comes ashore.
Tsunamis can travel upstream in coastal estuaries and rivers, with damaging waves extending farther inland than the immediate coast.
- A tsunami can occur during any season of the year and at any time, day or night.
- To save lives, scientists established the
Pacific Tsunami Warning System, based in
Hawaii, in the U.S.A. Its network of
earthquake detectors and tide gauges
detects quakes that may cause a tsunami.
We can't tame the tsunami but we can
learn when it's coming and escape the sea
monster's fury. tsunami ...
Important Facts to
Know about Tsunamis
- Tsunamis that strike coastal locations in
the Pacific Ocean Basin are most always
caused by earthquakes. These earthquakes
might occur far away or near where you
- Some tsunamis can
be very large. In coastal areas their
height can be as great as 30 feet or more
(100 feet in extreme cases), and they can
move inland several hundred feet.
- All low-lying
coastal areas can be struck by tsunamis.
- A tsunami consists
of a series of waves. Often the first
wave may not be the largest. The danger
from a tsunami can last for several hours
after the arrival of the first wave.
- Tsunamis can move
faster than a person can run.
- Sometimes a
tsunami causes the water near the shore
to recede, exposing the ocean floor.
- The force of some
tsunamis is enormous. Large rocks
weighing several tons along with boats
and other debris can be moved inland
hundreds of feet by tsunami wave
activity. Homes and other buildings are
destroyed. All this material and water
move with great force and can kill or
- Tsunamis can occur
at any time, day or night.
- Tsunamis can
travel up rivers and streams that lead to
A Survey of Great
Here are some of the more destructive recent tsunamis.
1929 Grand Banks, Canada
1946 Aleutian Islands, Alaska
1952 Kamchatka Peninsula, Russia
1957 Aleutian Islands, Alaska
1964 Prince Williams Sound, Alaska
of the Tsunami Warning System: :
How are people in coastal areas warned
It is by The Tsunami Warning System,
An international effort to save lives and protect
Tsunami Warning Centers
As part of an international cooperative effort to
save lives and protect property, the National
Oceanic and Atmospheric Administration's (NOAA)
National Weather Service operates two tsunami
warning centers. The Alaska Tsunami Warning
Center ATWC) in Palmer, Alaska, serves as the
regional Tsunami Warning Center for Alaska,
British Columbia, Washington, Oregon, and
The Pacific Tsunami Warning Center( PTWC) in Ewa
Beach, Hawaii, serves as the regional Tsunami
Warning Center for Hawaii and as a
national/international warning center for
tsunamis. The PTWS is composed of 26
international Member States that are organized as
the International Coordination Group for the
Tsunami Warning System in the Pacific. The
objective of the PTWS is to detect, locate, and
determine the magnitude of potentially
tsunamigenic earthquakes occurring in the Pacific
Basin or its immediate margins. Earthquake
information is provided by seismic stations
operated by PTWC, ATWC, the U.S. Geological
Survey's National Earthquake Information Center
and international sources. If the location and
magnitude of an earthquake meet the known
criteria for generation of a tsunami, a tsunami
warning is issued to warn of an imminent tsunami
hazard. The warning includes predicted tsunami
arrival times at selected coastal communities
within the geographic area defined by the maximum
distance the tsunami could travel in a few hours.
A tsunami watch with additional predicted tsunami
arrival times is issued for a geographic area
defined by the distance the tsunami could travel
in a subsequent time period.
If a significant tsunami is detected by sea-level
monitoring instrumentation, the tsunami warning
is extended to the entire Pacific Basin.
Sea-level (or tidal) information is provided by
NOAA's National Ocean Service, PTWC, ATWC,
and other participating nations of the PTWS.
The NOAA Weather Radio System, based on a large
number of VHF transmitter sites, provides direct
broadcast of tsunami information to the public.