A tsunami is a series of giant ocean waves produced by a major underwater or coastline disturbance such as an earthquake or volcanic eruption. Tsunamis can occur in all oceans, but they are most common in the Pacific. Areas thousands of miles from an earthquake can be struck by a resulting tsunami.

The waves appear to be normal ocean waves until they approach the coastline, where a gigantic wall of water can build on the ocean surface. Tsunamis reaching heights of more than 100 feet have been recorded. The waves may last several hours, with 20 or 30 minutes between waves.