How Does a Tsunami Work? Tsunamis have three main causes: submarine landslides, earthquakes, or underwater volcanic eruptions. These displace a massive amount of water. The water moves up above the surface, and gravity pulls it back down. The energy from this causes ripples that move outward in a circle. A tsunami isn’t one wave, it’s a chain of waves. Think about the ripples in a pond. And even worse, the first wave isn’t the deadliest. They only get stronger as the later waves move onto land. Tsunamis are harmless for 95% of their life. The energy of the tsunami runs through the entire depth of the ocean. It only becomes deadly when the ocean floor becomes shallow, and all that energy compresses into a smaller amount of water. Tsunamis move at the speed of a commercial airliner (about 500mph). As the ocean floor becomes shallower, they slow down, and increase in height. On land, they move at the speed of a car (20-30mph).
The Energy Behind the Tsunami Some lunatics claimed that if someone detonates an atomic bomb under the ocean surface you can cause a tsunami. One atomic bomb? The 2004 earthquake produced a force equivalent to 450,000 kilotons of TNT, or 23,000 Hiroshima atomic bombs. See all those zeros?
The earthquake also happened in a very shallow part of the ocean, and very close to the coast of Indonesia. Every condition needed for utter destruction had already been satisfied.
