A tsunami has four general stages: initiation, split, amplification, and run-up.

During initiation, a large set of ocean waves are caused by any large and sudden disturbance of the sea surface, most commonly earthquakes but sometimes also underwater landslides.

In the split stage, the initial set of waves is split into two, one set that travels out into the deep ocean and another that travels toward a nearby coast.

In stage three, amplification, the height of the tsunami increases, and the distance between two adjacent crests (high points) as it travels toward the coast, so the first wave of the tsunami becomes steep.

In the last stage, a peak of the tsunami hits shore . The reason this stage is called the run-up stage is that run-up is the term used to describe the measurement of the height of the water on the shore . Once on land, part of the tsunami is reflected back into the ocean, and another part is trapped in waves that travel back-and-forth near the shore.

Tsunamis are ocean waves with a very long period, or distance between wave crests. These waves form when a large amount of water is displaced, for example by a landslide into the ocean, or by an earthquake that moves the seafloor. The energy associated with the displacement of water (potential energy) is turned into a wave (kinetic energy).

After the water is displaced, the tsunami waves travel away from their source area. They have a low amplitude (height), but they travel extremely fast. In deep water, tsunamis pose no risk: you would almost certainly not feel a tsunami wave on a boat in the deep ocean. As the tsunami wave reaches shallower water, however, the wave slows down and the wave height increases. This process generates the potentially devastating waves that we associate with tsunamis. Tsunamis are associated both with large waves, and with moving a large volume of water onto land.

For a tsunami to form there has to be a source of energy to move the ocean water to create tsunami waves. Usually earthquakes, and sometimes underwater landslides, can give the water enough of a push to make a large tsunami.

A tsunami will then move quickly over open water. When the waves are moving across the open ocean the tsunami usually isn't so high. However, once the waves move towards shallower water the waves will grow until they hit land, but they will also slow down as well.

A tsunami is basically a pressure wave that causes a body of water to overflow its shores.

To give an example, take a bath. While lying with most of your body under water, raise your hand above the water. Then, suddenly, drop your hand under the water. You will notice a small wave extend out from where your hand was above the surface, and that wave will cause the water level of the tub to go up and down when the wave hits the edge of the tub. This wave is a very small tsunami. The reason why tsunamis in the ocean are so deadly is because instead of the source being the movement of something the size of your fist, it is instead something the size of a mountain (or even larger!).