With wave speeds that can reach as much as 435 miles per hour, a tsunami can travel as far inland as 10 miles, depending on the slope and the shape of the shoreline that it is traveling across. Ships traveling in the deep ocean may pass over a tsunami and not even notice it because a tsunami can cause the waves to be as little as 2 feet high where the water is very deep.
A tsunami occurs most often as an earthquake on the sea floor. This earthquake can trigger a wide variety of phenomenon, including undersea landslides and undersea volcanic eruptions, and it can even affect meteorites. When a sudden change in the seafloor occurs, it can cause the ocean to flow away from the disturbance and quite often towards land while creating large crashing waves.
The most common thing that people should look for with a tsunami is when the water along the shoreline recedes further out than normal. By this time, it is much too late to respond because the water will begin to rush in within as little as 5 minutes. Once a tsunami occurs, it is important to stay off the beach because there will likely be larger waves to follow.