National Geographic : 1998 May
impending disaster. Soon waves were hitting the walls of the sweat lodge." Since the sweat lodge was at least 30 feet above sea level, Carver is convinced that the Yurok were describing a tsunami that struck following an earthquake along the Cascadia subduction fault. Tsunamis are sometimes erroneously called tidal waves but have noth ing to do with tides. The word "tsunami" means "harbor wave" in Japanese, and they are natural responses to earthquakes. Such earthquakes occur when all or part of the subducting plate gets locked against the Then a geologist named Brian Atwater began publishing disquieting evidence he had found in the coastal marshes of Washington State. I MEET ATWATER at his campsite on the central Washington coast on a gray, lightly raining morning in June. He straps a canoe onto his pickup, and we drive with a team of students toward the estu ary at Copalis Beach. Atwater, a self-effacing, bearded geologist with the United States Geo logical Survey (USGS) in Seattle, wants to show me his ghost forest. overlying plate, and strain builds. The sea floor plate subsides, while the land on the overlying crust slowly buckles upward. When the lock eventually breaks, the subsided sea floor rebounds, displacing many cubic miles of ocean in a series of tsunami waves. At the same time, the elevated land along the coast drops. Until the mid-1980s there was no evidence that a subduction quake had ever hit Cascadia. Most scientists figured the Juan de Fuca plate was diving smoothly beneath the continent.