The Forecast: Tsunamis don’t happen on their own—they’re triggered by earthquakes, underwater landslides, even meteor impacts. But once triggered, the waves, which can range from ten to more than a thousand feet high, strike without warning. Typically, there are one or two localized tsunamis each year and one monster, like the March wave that devastated Japan’s northeast coast. In the U.S., the West Coast, Hawaii, and Alaska are at highest risk due to seismic activity in the Pacific Ocean’s Ring of Fire, which produces nearly 90 percent of the world’s earthquakes.
Stats: 1,740—height, in feet, of the tallest tsunami ever recorded, in Lituya Bay, Alaska, in 1958.
Worst-Case Scenario: Being caught off-guard on the beach. Ideally, sensors deployed in the ocean trigger sirens and warning systems that give communities enough notice to leave the coast. But in many parts of the world, you have to look to nature. A tide going out or coming in at an unusual hour is a sure sign of a tsunami. Get to the upper floor or roof of a sturdy building, climb a tree, or, as a last-ditch effort, hold on to a life jacket, cooler, or other buoyant object. Remember: tsunamis can last ten hours, and the first wave isn’t always the worst.
Smart Play: If you’re on the water in a kayak, sailboat, or motorboat before a tsunami hits, get as far out to sea as you can. You’ll still be lifted by the swell, but if you’re in deep enough water, you won’t be pushed ashore.