Scientists have revealed the three most dangerous tsunami zones in the United States—and the threat is far more real, and far closer, than most people think. The Pacific Northwest, East Coast, and Gulf Coast all sit in the crosshairs of potentially catastrophic waves triggered by underwater earthquakes, landslides, and rising sea levels. Millions of people live in the path of these looming disasters. And while tsunamis may feel like rare, distant events, they’re more like ticking time bombs waiting to be set off.