What is a Tsunami

A tsunami is a series of enormous waves created by an underwater disturbance such as an earthquake, landslide, volcanic eruption, or meteorite. A tsunami can move hundreds of miles per hour in the open ocean and smash into land with waves as high as 100 feet or more.

From the area where the tsunami originates, waves travel outward in all directions. Once the wave approaches the shore, it builds in height. The topography of the coastline and the ocean floor will influence the size of the wave. There may be more than one wave and the succeeding one may be larger that the one before. That is why a small tsunami at one beach can be a giant wave a few miles away.

All tsunamis are potentially dangerous, even though they may not damage every coastline they strike. A tsunami can strike anywhere along most of the U.S. coastline. The most destructive tsunamis have occurred along the coasts of California, Oregon, Washington, Alaska, and Hawaii.

Earthquake-induced movement of the ocean floor most often generates tsunamis. If a major earthquake or landslide occurs close to shore, the first wave in a series could reach the beach in a few minutes, even before a warning is issued. Areas are at greater risk if they are less than 25 feet above sea level and within a mile of the shoreline. Drowning is the most common cause of death associated with a tsunami. Tsunami waves and the receding water are very destructive to structures in the run-up zone. Other hazard include flooding, contamination of drinking water, and fire from gas lines or ruptured tanks.

When, where, how, what kind, how often?
A tsunami can occur anytime of the day or year.
It will happen in coastal communities within distance of subduction zone.
It is caused by an undersea earthquake near or far from the Oregon coast.
A tsunami could last up to 12 hours.
There are two kinds of tsunamis. One is a local event (off the Oregon coast) and a distant event (an earthquake from the Oregon coast).
The last event local event occurred in January 1700. In Oregon, geologists state that a local tsunami would occur every 300-500 years.