Tsunamis are caused by an inclued earthquake,landslides, or volcanic eruptions. In the deep ocean, the tsunami wave may only be a few inches high. The tsunami wave may come gently ashore or may increase in height to become a fast moving wall. If there see the water recede quickly from a beach or feel an earthquake near the beach you should move to higher ground. tsunamis happen in the Pacific Ocean, in Alaska, Chile, Philippines, Japan etc.