When was tsunami caused

Tsunamis travel swiftly across the open ocean. The map on this page shows how a tsunami produced by an earthquake along the coast of Chile in traveled across the Pacific Ocean, reaching Hawaii in about 15 hours and Japan in less than 24 hours.

Many people have the mistaken belief that tsunamis are single waves. They are not. Instead tsunamis are "wave trains" consisting of multiple waves. The chart on this page is a tidal gauge record from Onagawa, Japan beginning at the time of the Chile earthquake. Time is plotted along the horizontal axis and water level is plotted on the vertical axis.

Note the normal rise and fall of the ocean surface, caused by tides, during the early part of this record.

Then recorded are a few waves a little larger than normal followed by several much larger waves. In many tsunami events, the shoreline is pounded by repeated large waves.

Tsunami Geology - What Causes a Tsunami? Article by: Hobart M. A tsunami is a series of ocean waves that sends surges of water, sometimes reaching heights of over feet These walls of water can cause widespread destruction when they crash ashore. These awe-inspiring waves are typically caused by large, undersea earthquakes at tectonic plate boundaries.

When the ocean floor at a plate boundary rises or falls suddenly, it displaces the water above it and launches the rolling waves that will become a tsunami.

Tsunamis may also be caused by underwater landslides or volcanic eruptions. Tsunamis race across the sea at up to miles kilometers an hour—about as fast as a jet airplane. At that pace, they can cross the entire expanse of the Pacific Ocean in less than a day. And their long wavelengths mean they lose very little energy along the way.

In deep ocean, tsunami waves may appear only a foot or so high. But as they approach shoreline and enter shallower water they slow down and begin to grow in energy and height. The tops of the waves move faster than their bottoms do, which causes them to rise precipitously.

When it does, it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors. Recognizing this phenomenon can save lives. A tsunami is usually composed of a series of waves, called a wave train, so its destructive force may be compounded as successive waves reach shore. The way one plate moves relative to another determines the type of boundary: spreading, where the two plates move away from each other; subduction, where the two plates move toward each other, with one sliding beneath the other; and transform, where the two plates slide horizontally past each other.

Subduction is the main cause of major tsunami events. There are subduction zones with associated deep-sea trenches off Chile, Alaska, Japan, and Indonesia, for example, that have produced large earthquakes and devastating tsunamis, many of which caused damage and loss of life in the Hawaiian Islands.

Part of the seafloor snaps upward as the tension is released. The entire column of seawater is pushed toward the surface, creating an enormous bulge.

As the water flattens out, giant ripples race outward. It can be generated by movements along fault zones associated with plate boundaries. The region where two plates come in contact is a plate boundary, and the way in which one plate moves relative to another determines the type of boundary:. Most strong earthquakes occur in subduction zones where an ocean plate slides under a continental plate or another younger ocean plate.

All earthquakes do not cause tsunamis. There are four conditions necessary for an earthquake to cause a tsunami:. Although relatively infrequent, violent volcanic eruptions represent also impulsive disturbances, which can displace a great volume of water and generate extremely destructive tsunami waves in the immediate source area. One of the largest and most destructive tsunamis ever recorded was generated in August 26, after the explosion and collapse of the volcano of Krakatoa Krakatau , in Indonesia.

This explosion generated waves that reached feet, destroyed coastal towns and villages along the Sunda Strait in both the islands of Java and Sumatra, killing 36, people. Tsunamis caused by extraterrestrial collision i. Scientists have calculated that if a moderately large asteroid, km in diameter, should strike the middle of the large ocean basin such as the Atlantic Ocean, it would produce a tsunami that would travel all the way to the Appalachian Mountains in the upper two-thirds of the United States.

On both sides of the Atlantic, coastal cities would be washed out by such a tsunami. An asteroid kilometers in diameter impacting between the Hawaiian Islands and the West Coast of North America, would produce a tsunami that would wash out the coastal cities on the West coasts of Canada, the U. The translations provided are automated by Google Translate and therefore may not be accurate. IOTIC will not be responsible for the discrepancies of the translated version of the website.

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