Tsunami how many minutes after earthquake

As the waves approach the coast, their wavelength decreases and wave height increases. On the open ocean, the wavelength of a tsunami may be as much as two hundred kilometers, many times greater than the ocean depth, which is on the order of a few kilometers.

In the deep ocean, the height of the tsunami from trough to crest may be only a few centimeters to a meter or more - again depending on the generating source. Tsunami waves in the deep ocean can travel at high speeds for long periods of time for distances of thousands of kilometers and lose very little energy in the process. The deeper the water, the greater the speed of tsunami waves will be.

At such high speeds, a tsunami generated in Aleutian Islands may reach Hawaii in less than four and a half hours. In , great tsunami waves generated in Chile reached Japan, more than 16, km away in less than 24 hours, killing hundreds of people. Jane Cunneen does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

The earthquake occurred off the west coast of southern Mexico 69 km below the surface, with a magnitude of 8. It will be some time before we know the full extent of the earthquake damage in Mexico.

Recent assessments recorded more than 60 deaths and significant damage. The earthquake also generated a tsunami with a series of waves over one metre high striking the Mexico coast over a period of more than six hours.

The wave travelled west across the Pacific Ocean towards New Zealand, but initial warnings triggered for that country have now been cancelled. Most earthquakes occur along the edges of tectonic plates, known as plate boundaries. The Mexico earthquake occurred where the Cocos plate is colliding with the North American plate.

An area of about by 50 km was pushed up by the earthquake, moving the water overlying it. The sea floor was uplifted by only a few metres , but this is enough to displace several cubic kilometres of water and send a series of waves outwards from the earthquake epicentre.

The tsunami waves travel away from the earthquake epicentre in all directions. The epicenter of the 9. Geological Survey, which monitors earthquakes worldwide. A violent movement of the Earth's tectonic plates displaced an enormous amount of water, sending powerful shock waves in every direction. Within hours killer waves radiating from the epicenter slammed into the coastline of 11 Indian Ocean countries, snatching people out to sea, drowning others in their homes or on beaches, and demolishing property from Africa to Thailand.

Tsunamis have been relatively rare in the Indian Ocean. They are most prevalent in the Pacific. But every ocean has generated the scourges. Many countries are at risk. In the wake of the Christmas weekend tsunami in the Indian Ocean, one of the worst disasters in history, National Geographic News examines the killer waves' causes and warning signs—information that can be a lifesaver in a tsunami zone.

More rarely, a tsunami can be generated by a giant meteor impact with the ocean. Scientists have found traces of an asteroid-collision event that they say would have created a giant tsunami that swept around the Earth several times, inundating everything except the mountains 3. The coastline of the continents was changed drastically and almost all life on land was exterminated.

Read the story. Tsunamis are fairly common in Japan and many thousands of Japanese have been killed by them in recent centuries. The first wave in a tsunami is not necessarily the most destructive. Tsunamis are not tidal waves. They are able to cross entire oceans without great loss of energy.

The Indian Ocean tsunami traveled as much as 3, miles nearly 5, kilometers to Africa, arriving with sufficient force to kill people and destroy property. Scientists say that a great earthquake of magnitude 9 struck the Pacific Northwest in , and created a tsunami that caused flooding and damage on the Pacific coast of Japan. Scientists are able to calculate arrival times of tsunamis in different parts of the world based on their knowledge of when the event that generated them occurred, water depths, and distances.

But the powerful shock wave of energy travels rapidly through the ocean as fast as a commercial jet. Once a tsunami reaches shallow water near the coast it is slowed down.

The top of the wave moves faster than the bottom, causing the sea to rise dramatically. In some places a tsunami may cause the sea to rise vertically only a few inches or feet. In other places tsunamis have been known to surge vertically as high as feet 30 meters. Most tsunamis cause the sea to rise no more than 10 feet 3 meters. The Indian Ocean tsunami caused waves as high as 30 feet 9 meters in some places, according to news reports.

In other places witnesses described a rapid surging of the ocean. Flooding can extend inland by a thousand feet meters or more. The enormous energy of a tsunami can lift giant boulders, flip vehicles, and demolish houses. Knowledge of the history of tsunamis in your area is a good indicator of what is likely to happen in a future tsunami event.

They may be more like a very rapidly rising tide. This may be accompanied by much underwater turbulence, sucking people under and tossing heavy objects around. Entire beaches have been stripped away by tsunamis. News reports so far suggest that more than , people may have lost their lives, many of them washed out to sea.