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The Shaking Ocean Floor The Shaking Ocean Floor When you think of an earthquake, what comes to mind? Most people think about earthquakes on land. They think of the ones that cause buildings to collapse and roads to split apart. Did you know that some earthquakes happen on the floor of the ocean? These earthquakes can produce a series of waves called a tsunami. Big earthquakes make larger waves. The waves are very long, and they can travel very quickly. So what exactly causes earthquakes on the ocean floor? Earth’s crust is like a puzzle. It is made of many pieces that are always moving. The pieces are called plates. The map shows Earth’s major plates. When one of these plates moves suddenly, the movement causes an earthquake, which we can feel as a shaking of the ground. Most earthquakes, including ones on the ocean floor, happen at the plate boundaries where different plates interact. A lot of people think all tsunamis are really tall. But remember, tsunamis are different sizes depending on the strength of the earthquake that causes them. In a deep ocean, a tsunami may be greater than 100 kilometers long, but less then 1 meter tall. But when a tsunami is close to a shore, the wave slows down. This causes the wave to grow. A tsunami may be as tall as 25 meters when it reaches a shore. When a tsunami hits land, it can destroy everything in its path. In 2004, the deadliest tsunami ever recorded hit the shores in parts of Asia. It was triggered by a major earthquake beneath the Indian Ocean. Years later, the area is still recovering from the damage caused by the tsunami. Scientists have developed a warning system to help protect people from larger, more dangerous tsunamis that come onto land. The system consists of two parts. First, a series of sensors detect the underwater earthquake. Then, a warning is sent out so people can leave the area. A warning system, if working properly, can often save many lives. Discovery Education Science © 2007 Discovery Communications, LLC