Tsunamis are caused by an underwater 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. The tsunami caused damage damage houses collapsed, ruins, people died,etc.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.