The most common source of a tsunami is an earthquake, although it can also be brought on by a meteorite, landslide, volcanic eruption, or abrupt changes in atmospheric pressure.¹⁾

A “wave train”—a series of waves collectively known as a tsunami—is what causes a tsunami. The “wave period,” which can last anywhere from a few minutes to two hours, is the interval between waves. Typically, the initial wave is not the strongest, and subsequent waves, like the fifth or sixth, may be much bigger.²⁾

For the first time, Greek historian Thucydides (460–395 B.C.) connected undersea earthquakes to tsunamis in his History of the Peloponnesian War.³⁾

Tsunami waves frequently only reach heights of one to three feet in the deepest parts of the ocean. It's possible for sailors to be completely unaware that a tsunami is passing under them.⁴⁾

Within 160 miles (250 km) of the tsunami's origin or within 30 minutes of the tsunami's generation, around 99% of all tsunami-related fatalities have occurred. Therefore, everyone in a coastal location should heed the natural signal that a tsunami may be approaching and escape low-lying coastal areas if they experience a significant earthquake.⁵⁾

The ocean may suddenly seem to drain away up to 30 minutes before a tsunami hits, although this is not always the case. The term “drawback” refers to the water receding as the tsunami's crest approaches the beach.⁶⁾

Hawaii, Alaska, Washington, Oregon, and California are the U.S. states most at risk from tsunamis.⁷⁾