On December 26, 2004, a disastrous tsunami struck many parts of South Asia. The scope of this disaster has resulted in an outpouring of aid throughout the world and brought attention to the science of tsunamis. "Tsunami" means "harbor wave" in Japanese, and the Japanese have a long history of tsunamis. The word "tsunami" brings to mind one towering wave but actually refers to a series of waves, most often caused by an undersea earthquake. Though less likely, an undersea landslide, a volcano, or even a large meteorite can also trigger a tsunami event. A magnitude 9.0 earthquake off the coast of Indonesia triggered the South Asia tsunami. According to the United States Geological Survey (USGS), this earthquake was the fourth largest in the world since 1900. The evolution of this tsunami beginning with its cause is traced in this article.