Tsunamis are formed by violent underwater earthquakes, landslides, volcanic eruptions, and, rarely, meteor impacts. These events cause sudden and drastic displacement of water, forming massive waves in the process.
Most tsunamis are caused by earthquakes. As a result, most tsunamis occur near or at fault lines. When a tsunami is generated, it is not only 1 wave. Instead it is a series of waves, known as a wave train. These waves travel together and can be up to 1 hour apart. Tsunami waves travel extremely fast with speeds of up to 500 miles per hour—the speed of a jet.
They can be as wide as 60 miles and cross entire oceans without losing momentum. When a tsunami is traveling, it may be less than a foot in height. This causes it to be unnoticed by sailors who are at sea. As the tsunami approaches land, it hits shallow water and begins to slow down. The top of the wave, however, continues travelling, causing the sea to rise dramatically. Tsunamis are extremely destructive on land. The waves can surge up to 100 feet in height and completely devastate a coastal area. The 2004 Indian Ocean Tsunami was the deadliest tsunami in human history, killing over 150,000 people.