A tsunami is a series of waves generated by a disturbance on the ocean floor. This disturbance can be caused by earthquakes, landslides, volcanic eruptions, explosions or meteorites. The waves have very long wavelengths, which can travel hundreds of miles across the ocean. As the waves reach the continental shelf, they can grow to be several meters in height and cause extensive destruction along the coastline.
Though they may travel at speeds over 500 miles per hour, tsunamis are hard to visually detect in the deep ocean. Early warning is essential to save lives. The National Oceanic and Atmospheric Administration has developed stations in the Pacific Ocean that are capable of detecting the passage of a tsunami with sea bottom pressure recorders. Warnings are then sent to areas predicted to be affected by the readings.
Before a tsunami hits, the ocean may recede, creating a barren landscape to which sightseers flock. Many have been killed when the water unexpectedly crashes back to shore in a huge wall. Tsunamis do not always create a crest. Sometimes they simply flood an area, rising inland well beyond the normal shoreline. The geography of an area has a huge impact on the effects of the tsunami. Some areas of coastline may experience little damage, while nearby areas may be devastated.