Buried trees on Pacific Northwest beaches
  provide insights into area's geology

       Author: Peter Fish
       Sunset Magazine  Issue: Feb, 2001

        NESKOWIN BEACH, OREGON--The tree roots reach across the sand like the tentacles of giant squid--the sort that destroy cities in science fiction flicks. Burly winter waves surge and retreat, but the roots remain immense.

       "I was walking with my family," Roger Hart says. "At first I thought the trees were driftwood. But they didn't move. I got curious."

       It does inspire curiosity, the long-buried ghost forest of roots and stumps that in the last few years has been exposed on this Oregon beach. It has also helped change dramatically what geologists think about the Northwest.

       Roger Hart is a marine geologist at Oregon State University, over the mountains in Corvallis. He was born near Boston, but research has taken him from the mid-Pacific to South Africa. Hart has a true geological mindset: When he looks at the beach, he sees not a pretty tableau but rather a clash of elemental forces.

       Some of these trees have been dated back twenty centuries.

       The fact that they're being gradually exposed on the beach indicates a change in the shoreline or possibly a landslide.  Last year, the Oregon coast proved that sort of thing still happens just because it rains.   An earthquake generated by tectonic processes or volcanic activity also could have moved that patch of ground.
        
       The Sitka Spruce grows only along the coast. (See Tree of the Month in this issue.

        During the 90's, Brian Atwter, a USGS geologist studied similar trees on the Washongton coast.  They dated to 1700 A.D.  A tsumani (tidal wave) hit Japan in that year.  The Japanese descriptions of the event provide evidence that the wave was generated from the other side of the Pacific.  The Cascadia subduction zone lies off the Oregon coast, and is the source you would look to for such things.  A subduction zone is a place where two continental plates collide.  One slides under the other, catches, builds up pressure, then suddenly breaks free and slides forward and down.  Undersea earthquakes cause the tidal waves and the ripple of the crust in the direction of dry land jiggle everything above sea level.

       Even now, not all of Hart's colleagues are convinced the Neskowin forest was buried by an earthquake. But it is now generally accepted that the Northwest coast is vulnerable to such a quake. "It could be 1,000 years from now," Hart says. "It could be tomorrow."

     Hart, these days, is concentrating  on the question of why the ghost trees were revealed.  Rising sea level, as in global warming, is one possibility since from the beach you can see other Sitkas not far above the sand.  That is problematic, since sea level is never a fixed thing, relating as it does to evaporation rates and the size of the polar ice caps.  (Something like a third to a half of Antarctica melts away and re-freezes each year.)   Global warmng and cooling is the natural state of things, with or without Man's intervention.

       The tide is coming in. Waves wash over the giant tree roots. "The Oregon coast is  tremendously scenic," Hart says, above the crash of surf. "But that's because of its geology. For 300 years we haven't had an earthquake here. Everyone thought that was good news. Well, now we know that it's a little more ambiguous."