What are facts on tsunamis?

Answer 1

• The word tsunami is a Japanese word, translated as "harbour wave". It is not a tidal wave.
• Tsunamis are usually caused by underwater earthquakes which result in massive displacement of water. They can also be caused by landslides displacing water, or even asteroid impacts.
• Tsunamis can travel thousands of kilometres before reaching land. Tsunamis can wipe out an entire city and kill a large number of people, particularly in countries where many people dwell and make their livingclose to the coast.
• Tsunamis occur most often along countries which border the Pacific "Rim of Fire", or "Ring of Fire'. One end of this region of high seismic and volcanic activity begins at New Zealand, heading northwest to Indonesia (completely bypassing Australia) and then west to Papua New Guinea and Indonesia, northeast along the Asian coastline, east to North America and then south along the western North American coastline. Roughly horse-shoe shaped, the Ring of Fire extends about 40,000km long, and tsunamis can be generated anywhere along this rim.
• Some tsunamis can be very large. In coastal areas their height can be as great as 10 to 30 m high, whilst the largest tsunami ever recorded was 524 metres high, or just over half a kilometre (Alaska, 1958).
• Tsunamis in excess of 100m high are called megatsunamis.
• All low lying coastal areas can be struck by tsunamis.
• A tsunami is actually made up of a series of waves which may arrive every 10 to 60 minutes. 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. Tsunami waves typically do not curl and break, so you should never try to surf a tsunami.
• Tsunamis can travel through deep water as fast as 950kph. However, their amplitude (height) is only about 1 meter with a wavelength of 200-300m. In deep water, a tsunami would be just barely perceptible, if at all.
• Sometimes a tsunami may cause the water near the coast to recede dramatically, exposing land which is usually submerged. This is a sure sign of an impending tsunami.
• There is no limit as to when a tsunami can hit - morning, noon, night, etc.
• In the Indonesian or "Boxing Day" Tsunami of December, 2004, waves reached heights of over 30 meters in Banda Aceh, evidenced by the complete stripping of the very tallest palm trees. In a minor tsunami, the waves may be only millimeters high.
• Some types of animals have an innate sixth sense which enables them to detect when a tsunami is going to occur: they will then head inland in the opposite direction.
• Tsunamis are accompanied by a loud roaring sound, described by witnesses as being similar to the sound of a train or aircraft.
• Once a tsunami reaches the shore, its wave length may be as much as 100km, compared to ordinary ocean waves of some 100 metres in length.
• After reaching shallower waters, tsunami lose their forward speed and hugely gain amplitude; their forward momentum is not lost by much, however.
• Unlike wind waves which "break" and move water in mostly a circular motion, tsunami waves have forward moving inertia, which carries the entire volume of the wave inland at high speed, much like a hurricane's storm surge.
• Depending on the severity, casualties can range from hundreds of thousands to none. In a catastrophic tsunami, the waves can be over 30m/98ft high. Moving faster than anyone can run, they churn a horrid mix of debris, from cars to pieces of homes, bodies and whatever else is not cemented to the ground; people are either crushed to death or drowned.
• Some types of animals have an innate sixth sense which enables them to detect when a tsunami is going to occur: they will then head inland in the opposite direction.
• Tsunamis do not have to be a certain height but have to be caused by a earthquake or something that is nothing to do with tides to be called a tsunami.
• On July 12, 1993 a magnitude 7.8 earthquake in the Sea of Japan produced tsunami that totally destroyed the southern half of Okushiri Island. Waves were greater than 30 feet and some could have been 100 feet. The earthquake was about 50 miles offshore and the tsunami arrived within minutes. 120 people died.
• In the USA, the states most at risk for Tsunami are California, Hawaii, Oregon and Washington.
• On 28 March 1964 an extremely large earthquake (magnitude 8.4) struck Alaska. It caused tsunami waves that were very destructive in southeastern Alaska, in Vancouver Island, Canada, and in the States of Washington, California and Hawaii. Waves ranged in size from 6 to 21 feet. The tsunami killed more than 120 people and damages costing more than $106 million. It was the costliest tsunami ever to strike the Western United States and Canada.
• Although a large asteroid impact is highly unlikely, scientists studying the possibility have decided that a moderately large asteroid or about 5-6 km in diameter falling in the middle of the Atlantic Ocean, would generate a tsunami that would travel all the way to the Appalachian Mountains in the upper two-thirds of the United States. Coastal cities would be wiped out by such a tsunami.

A tsunami is usually caused by an earthquake but can also be caused by a volcanic eruption, landslide, and rapid changes in atmospheric pressure even meteorite shower.The time period between waves is called the "wave period" and can be between a few minutes and two hoursThe first wave is usually not the strongest, and later waves, such as the fifth or sixth, may be significantly larger

Answer 2

The typical cause is an earthquake under the ocean floor. Tsunamis can also be caused by huge landslides into bodies of water, or by the impact of a large enough meteorite into an ocean or very large body of water. These things produce a wave that shifts not just a few meters of surface water, but the entire column of water from the floor to the surface. They contain enormous amounts of energy. Tsunamis can push huge amounts of water over islands and coastal regions causing the deaths of hundreds of thousands or millions of people, and they can cause millions or even billions of dollars worth of damage. Depending on whether the leading element of the tsunami is a trough or a crest (it can be either) there may be an eerie ebbing or pulling back of the water along the shore; it must appear to observers like an unnatural pulling back of the tide. This would happen if the leading element is a trough. If you ever witness this, run with all your might; seek high ground.

Underwater earthquakes, volcanic eruption or land slides.

Answer 3

Beginning of a tsunami wave

Sometimes plate boundaries abruptly deform and displace the overlying water vertically. Subduction earthquakes are efficient in generating a tsunami. In the 1940s, an earthquake measuring 7.8 on the Richter scale gave rise to a tsunami. Explosive volcanic action, landslides and impact events can also start a tsunami. The water wave may reach 50 to 150 meters and cover a height of 500 meters on local mountains. A "megatsunami" is caused by large landslides. The displaced water mass moves under the effect of gravity. This water radiates across the ocean similar to ripples in a pond.

Signs that a tsunami is approaching

• if an earthquake takes place near a body of water, it means that a tsunami will follow in a short time
• if the water along the shoreline recedes dramatically and exposes usually submerged areas it should be inferred that this is the trough of the tsunami and a crest will follow after a few seconds or minutes
• some large animals like elephants hear the noise of the tsunami and move in the opposite direction towards inland
• computer models can also foresee tsunami arrival and impact depending upon knowledge of the event that caused it and the shape of the oceanbed
• there is a loud roar similar to a train or aircraft

Tsunami warning system

Such systems comprise of two parts:

• a network of sensors to detect tsunamis
• a communications infrastructure to provide alarms for evacuation of coastal areas

There exist international and regional tsunami warning systems. The underlying principle used in both is that tsunamis move at a speed of 0.14 to 0.28 km/sec while seismic waves of 4 km/sec. Thus, when an earthquake is confirmed, there is sufficient time to predict a tsunami.

Reducing the effect of a tsunami

• Japan builds tsunami walls of 4.5 meters height in populated coastal areas
• floodgates and channels are built to redirect the water from the tsunami
• a tree cover is made on the shore

These measures slow down and moderates a tsunami. However, they cannot totally prevent the destruction and loss of life.

Records related to tsunami

• The maximum death toll due to tsunami has been 283,000 in 2004 in the Indian ocean.
• The second largest has been 100,000 in 1755 in Portugal, Morocco and the United Kingdom.
• The third largest is 70,000 in 1908 in Italy.

In the Indian Ocean, an earthquake of 9.0 magnitude on the Richter scale took place. The epicenter was close to the west coast of the Indonesian island of Sumatra. The Earth's tectonic plates moved violently and displaced a large quantity of water. Powerful shock waves were sent in all directions. At some places, these waves reached a height of 9 meters. Within a span of some hours, killer waves hit the coasts of 11 Indian Ocean countries and devastated properties from Thailand to Africa.

Other tsunami facts

At the deepest point in the ocean, Tsunamis can have a speed of 600 mph. Close to the shore, this speed reduces to 30 to 40 mph. This energy of the wave's speed is transformed to increased height and sheer force. These waves can be as long as 100 kilometers and one hour apart. They can cross huge oceans without much loss of energy. Tsunamis can take place at any time in night or day. They can move up the rivers and streams that end up in the ocean. Tsunamis move faster than a human being.

Megatsunami

If the waves range from 40 meters to more than 100 meters, they are called as a "megatsunami". When they reach land, they acquire more height due to the force of impact. They are also called as "iminami" or "wave of purification". Tsunami is a Japanese word with the English translation: "harbour wave". In the past, tsunamis have been referred to as "tidal waves" or "seismic sea waves". The term "tidal wave" is misleading; even though 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 gravitational influences of the moon, sun, and planets.) The term "seismic sea wave" is also misleading. "Seismic" implies an earthquake-related generation mechanism, but a tsunami can also be caused by a non-seismic event, such as a landslide or meteorite impact. Tsunamis can have wavelengths ranging from 10 to 500 km and wave periods of up to an hour. As a result of their long wavelengths, tsunamis act as shallow-water waves. In the deep ocean, a tsunami has a small amplitude (less than 1 metre) but very long wavelength (hundreds of kilometres). This means that the slope, or steepness of the wave is very small, so it is practically undetectable to the human eye. However, there are ocean observing instruments that are able to detect tsunamis.

Answer 4

they are big waves that form because of an earthquake. they can be up to 30 meters high and before they hit all the water will be sucked in so you can see all the sea urchins and such but you should probably evacuate if you see that. they can travel up to 500 mph underwater but if you were on a boat right above a passing one you wouldn't feel it. they normally form on convergent boundaries because convergent boundaries have bigger earthquakes. transform and divergent boundaries can have them too but they will only be like 3 feet high. Hope I helped (by the way I am 12)

Answer 5

its caused by a sudden change on the sea floor.

Answer 6

That they are just underwater earthquakes

Answer 7

Tsunamis happen when tectonic plates shift