A tsunami (tsoo-NAH-mee) is a series of enormous waves caused by a major disturbance of a body of water. This disturbance can be caused by earthquakes, volcanic eruptions, submarine landslides, coastal rock falls or a large asteroid impacting the ocean. Tsunamis are also known as seismic sea waves and are mistakenly called “tidal waves”.
Dependent on the distance of the tsunami from its source, it may be classified as a:
- Local tsunami:
A local tsunami is one that originates from within about 100 km or less than 1 hour tsunami travel time from the impacted coastline. Local tsunamis can result in a significant number of casualties since authorities have little time to warn/evacuate the population.
- Regional tsunami:
A regional tsunami is one that is capable of destruction in a particular geographical region, generally within 1,000 km from its source. Regional tsunamis can arrive to affected coastlines within 1-3 hours of being generated, however, as with local tsunamis, due to the limited warning time they can still prove very destructive and deadly.
- Tele-tsunami/Ocean-wide tsunami/Distant tsunami:
A tsunami originating from a source, generally more than 1,000 km or more than 3 hours tsunami travel time from the impacted coastline is called an ocean-wide or distant or tele-tsunami. These tsunamis are less frequent, but more hazardous than regional tsunamis, as they usually start as a local tsunami that causes extensive destruction to a shoreline near the source, and the waves continue to travel across an entire ocean basin with sufficient energy to cause additional casualties and destruction on shores more than a 1,000 km from the source. These tsunamis have the ability to cause widespread destruction, not only in the immediate region but across an entire ocean. All ocean-wide tsunamis have been generated by major earthquakes.
Time travel chart of - Great Lisbon (Portugal) earthquake generated tele-tsunami of 1755. Travel time to Barbados was approximately 7 hours with wave heights of 2 metres.