Tsunamis happen primarily due to sudden movements on the ocean floor that displace large volumes of water. The most common cause is large underwater earthquakes, where tectonic plates shift abruptly, pushing water upward and creating powerful waves. Other causes include underwater landslides, volcanic eruptions that collapse or push material into the ocean, and more rarely, meteorite impacts. These movements disturb the ocean surface and send waves radiating outward at high speeds, which grow in height as they approach shallow coastal areas, leading to the devastating waves known as tsunamis.