Facts about Tsunami

A tsunami is a series of sea waves caused by an underwater earthquake, landslide, or volcanic eruption. More rarely, a tsunami can be generated by a giant meteor impact with the ocean.

A tsunami is not just one wave but a series of waves or a “wave train.”

Many witnesses say a tsunami sounds like a freight train.

When the ocean is deep, tsunamis may be less than a foot high on the ocean’s surface, can travel at speeds up to 500 mph without being noticed and cross the entire ocean in less than a day.

Once a tsunami reaches the shallow water near the coast, it slows down. The top of the wave moves faster than the bottom, causing the sea to rise dramatically, as much as 100 feet at times. Tsunami waves can be as long as 60 miles and be as far as an hour apart. These waves can cross entire oceans without losing much energy.

Flooding can reach land 1000 feet (300 meters) from the coastline and the dangerous waves have enough force to lift giant boulders, flip vehicles, and demolish houses.

Scientists can accurately estimate the time when a tsunami will arrive almost anywhere around the world based on calculations using the depth of the water, distances from one place to another, and the time that the earthquake or other event occurred.

Hawaii is the U.S. state at greatest risk for a tsunami – they get about one per year and a damaging one every seven years. The biggest tsunami that occurred Hawaii happened on April 1, 1946, where the Coast of Hilo Island was hit with 30 foot waves coming in at 500 miles per hour. 170 people died as a result.

In 2004, the Indian Ocean tsunami was caused by an earthquake that is thought to have had the energy of 23,000 atomic bombs. Within hours of the earthquake in 2004, killer waves radiating from the epicenter slammed into the coastline of 11 countries, damaging countries from east Africa to Thailand. By the end of the day, the tsunami had already killed 150,000 people. The final death toll was 283,000.

Not counting the 2011 tsunami in Japan, there were 26 tsunamis that killed at least 200 people or more in the last century.