Tsunamis -- giant waves triggered by earthquakes and volcanoes -- can't be prevented and they can't be predicted. The only protection for a growing coastal population is a warning to evacuate.
A series of Pacific Ocean tsunamis over the last century fueled the establishment of an ocean-wide warning network. But the Indian Ocean, where tsunamis are less common, has no such system. So when earthquake specialists in the United States and elsewhere saw the first signal of the giant Dec. 26 quake, they had no way of knowing whether a tsunami was under way. And even if they had known about the tsunami, they had no way to alert coastal communities that titanic waves were racing at them -- as fast as a jet plane.