The chance of that happening at Mount Rainier is 0.2 percent. Beyond that, Hoblitt said, not enough is known to predict when Mount St. Helens will reawaken. But a new study, which Hoblitt is about to publish in the Geological Society of America Bulletin, shows the mountain has spent a restless past 500 years. Mount St. Helens has barely napped. In an eruption you can learn in minutes what would otherwise take years.
Weather patterns affect the ring width, and they do it over a broad area.
Back in the laboratory, the wood samples were dried and sanded. Fragile pieces were impregnated with warm paraffin. Then the wood was sliced into cross sections and matched against a master tree ring, supplied by one huge, old Douglas fir. The results shed new light on Mount St. Helens' recent past, from 1479 to the present. By studying, we learn frequency, types of eruptions and extent of the area affected.