A large wave that is produced by the sudden displacment of a large volume of water. This type of displacement is usually caused by an earthquake, but can also be produced by: submarine landslides, subaerial landslides, explosive volcanic eruptions, iceberg calving, atmospheric pressure changes or asteroid impacts. These events suddenly depress or elevate a large volume of water, then gravity causes the energy of that displacemenet to propagate away from the source. Most tsunamis originate in the ocean but they can be produced in smaller bodies of water. Tsunamis travel at high speeds for great distances (often crossing ocean basisns) and can cause great destruction when they reach land.