Describe how a tsunami is formed and how it can travel great distances at great speeds.

A tsunami is a shallow-water wave that originates on the seafloor when movement of the earth along fault lines displaces water. Tsunamis can also be caused by landslides, icebergs falling from glaciers, volcanic eruptions, asteroid impacts, and other direct displacements of the water surface. The oscillating ocean surface generates progressive waves that radiate from the epicenter in all directions. Tsunamis are extremely fast. For example, the 2004 tsunami traveled as fast as 470 miles per hour. The speed that a tsunami travels depends on the depth (d) of the water and the acceleration due to gravity (g) and can be calculated by taking the square root of depth times acceleration. Since tsunamis that are formed by faulting of the seafloor originate at great depths (a typical Pacific abyssal depth (d) is 4,600 meters), they can travel at very rapid speeds.