America's Pacific Northwest has relatively few earthquakes—only a handful each year that cause even moderately noticeable shaking. But a couple decades ago, scientists discovered a geological feature running along the coast that in other parts of the world regularly triggers massive earthquakes of 8.0 magnitude and higher. Were there once massive earthquakes in this part of the world? Geologists think there were. Now a small group of scientists are studying things that you might not think have anything to do with earthquakes—marsh soil, ocean sediments, landslide debris, and ghost forests—and they have reason to believe that the Pacific Northwest is likely not as idyllic as it was once assumed. The population is likely in grave danger of a massive earthquake at some point. What can be done? The big one can't be stopped, but scientists are working tirelessly to learn as much as they can to prepare.