Gordon Jacoby A team led by scientists at Columbia's Lamont-Doherty Earth Observatory has exploited an unusual piece of evidence, the roots of trees, to discover ancient earthquakes in the Pacific Northwest. Calif. The research strongly corroborates a growing body of evidence that the region from northern California to Vancouver Island, though unaffected by the seismically active San Andreas fault, is also subject to earthquakes.
Tree roots are a desperation tool.
Roots, on the other hand, often have many centers and grow irregularly. Their rings are less distinct and many are missing or don't form neat circular patterns. Nevertheless, we could piece together zones of undistorted growth, which allowed us to reconstruct the roots' growth record and the years, relative to each other, in which they died. The scientists also found buried and preserved marsh plants that once stood at or above the high-tide level until the area subsided about 2 to 5 feet. The fragile plants were all preserved standing unwilted in growth position, indicating that they had been suddenly submerged, covered with sediments and preserved.