On December 26, 2004 a 9.1 magnitude earthquake near the Indonesian island of Sumatra generated a massive tsunami that propagated across the planet. This simulation, using the NOAA MOST model for predicting how and when tsunamis will travel across the ocean, shows the series of waves generated by the tectonic megathrust. Bright colors indicate positive wave heights, dark colors are the troughs, or depressions in the sea surface. When in deep water, tsunami waves move very quickly (up to 1,000 kph) and with a low wave height. As they approach the coast and the depth of the ocean decreases, the wave slows down and mounds up. In this case, the maximum wave height exceeded 30m in some locations. It is estimated that over 250,000 people died in the event. Notice how the ocean floor topography (bathymetry) interacts with the wave, causing rippling, and bending the direction of movement.