What does Tidal Waves or "tsunami" mean?
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• A tidal wave is an unusually high sea wave that follows an earthquake or volcano.
• 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, extraterrestrial, gravitational influences of the moon, sun, and planets. Tsunami can also be caused by a nonseismic event, such as a landslide or meteorite impact.
• 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 "wave."
• 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 significant.
• 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 or more.
• 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 live.
• 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 injure people.
• Tsunamis can occur at any time, day or night.
• Tsunamis can travel up rivers and streams that lead to the ocean.
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A Survey of Great Tsunamis
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
1960 Chile
1964 Prince Williams Sound, Alaska
1975 Hawaii

How are people in coastal areas warned about tsunamis?

It is by The Tsunami Warning System, An international effort to save lives and protect property.

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 California.

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.

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