Cascadia's Fault - Jerry Thompson [41]
If the Little Salmon fault was active, then the Gorda plate—which had caused the cracks—had to be active as well, pushing its way underneath California while North America plowed west. The subduction along Cascadia’s fault had not “foundered,” and the plates had not stopped moving. At least that was the conclusion I drew from reading the science papers and from interviewing both Plafker and Carver.
Taken as a whole, the Humboldt Bay power project had a significant but unintended consequence. Building a reactor on top of a crack in the crust—a crack directly related to the Cascadia Subduction Zone just offshore—generated the new science that provided the first physical evidence that the northern section of the California and Pacific Northwest coast faced the same kind of tectonic disaster as the ones that happened in Alaska and in Chile.
If I’d been a journalist in California back in the 1970s, I like to think I would have turned this story into headline news. But the immediate impact of these discoveries confirming continental drift was almost nil. The story of Cascadia’s fault got lost in the controversy over nuclear power. Fortunately the scientists on the ground knew they were working on significant stuff and refused to quit.
It was the heady, meaningful kind of research that made it an exciting time to be a geologist—especially in the Pacific Northwest. Frank Press may have changed his mind, but many others in the science community still refused to buy the new geology. Even when the top half of a mountain in southern Washington State exploded, only a handful of researchers recognized the distinct sound of Cascadia’s smoking gun.
CHAPTER 8
Mount St. Helens: Cascadia’s Smoking Gun?
Even though geologists and volcanologists saw it coming, there was no way to prepare for the impact of watching a mountain explode at close range. Mount St. Helens—roughly ninety miles (145 km) south of Seattle and fifty miles (80 km) northeast of Portland—blew steam and dust for two months as a bulge of hot rock sprouted like a giant goiter on its north face. At the same time, the ground trembled and shook. People in downtown Portland turned the prelude into a spectator sport.
Government officials issued repeated warnings to evacuate the hills and valleys around the volcano as the frequency of tremors began to increase. Almost everybody did leave, except for an eighty-three-year-old recluse named Harry Truman who had lived in the woods near the mountain for more than fifty years and decided to stay close to his cabin. The media fell in love with him, a tragic hero in the making. A thirtyyear-old volcanologist named David Johnston was collecting data until the very last minute. His final words, “Vancouver! Vancouver! This is it!” were shouted into a walkie-talkie and received at the USGS volcano observatory in Vancouver, Washington, across the Columbia River from Portland, only moments before the eruption. Neither man was seen again.
At 8:32 a.m. on Sunday, May 18, 1980, the volcano started coming apart. A magnitude 5.1 earthquake caused the bulging north side of the mountain to collapse where a new lava dome had been growing. The collapse caused the largest landslide of rock and ice and volcanic mud ever recorded in the continental United States—9,600,000 cubic yards (7,340,000 m3) of boulders, muck, trees, and other debris was swept 17 miles (27 km) downhill into the Columbia River. With the face