This photo was taken by Dr. Sarah Sterling a few weeks back in a salt marsh west of Port Angeles. The sand layers at inch 26 and inch 28.5 on the ruler are unequivocally related to tsunamis, which push marine sands up into the salt marsh. Nearly identical sand layers are found in Discovery Bay, east of Port Angeles. The layers shown here are probably from tsunamis that happened hundreds of years ago.
The scale of these layers suggest a pretty substantial tsunami that may be associated with a rupture along the Cascadia subduction zone, just 50 miles off of our coast. Seeing these layers was a reminder to me that someday - perhaps sooner, or perhaps later - we (the Olympic Peninsula) are going to experience another of these big earthquakes and/or tsunami. And the evidence from this photo and from Discovery Bay suggests that tsunamis here can be of a scale to powerfully affect the entire shoreline of the Strait of Juan de Fuca.
I bring this up as a reminder - the news is filled these days with hand-wringing and nail-biting regarding the landfall of debris from the March 2011 Tohoku tsunami on our shores. Tsunami debris is a hazard, no doubt. Pile enough plastic on the beach and bad things happen. Enough of it in the water probably poses a toxicity risk, not to mention endangering wildlife and even creating navigation hazards. But I find that I cannot wholeheartedly agree with Chris Pallister, who runs an organization dedicated towards cleaning debris from the shores of Prince William Sound, who was quoted in an article today saying, "I think this is far worse than any oil spill that we've ever faced on the West Coast or any other environmental disaster we've faced on the West Coast". That statement ignores the environmental problems associated with the huge volumes of marine debris that enter the ocean EACH YEAR (far more plastic debris is probably released into the ocean as non-point pollution than from the Tohoku tsunami)and also downplays the devastation associated with large oil spills. The statement also seems to downplay the risk that we face from seismic events and tsunami, and I can't even give Chris the benefit of the doubt and assume that he is talking about events only in recent memory. Its only been 48 short years since an earthquake and tsunami wrecked SE Alaska, killing 119 people in the process.
The calls for greater preparedness for the tsunami debris are warranted. We will have to put our collective shoulder to the wheel to get beaches cleaned up, and some intervention by state and federal government may be necessary to deal with big items, toxic material or invasive species. But those loud calls, in my humble opinion, should be accompanied by, and I would argue overshadowed by, louder calls for better preparation for a local seismic event and tsunami...
As the Coastal Hazards Specialist for Washington Sea Grant I spend my time on research, education and outreach on topics like chronic erosion, climate change, tsunami and other coastal hazards. Current projects include:
1) monitoring the shoreline of the Elwha River delta to detect changes due to the Elwha Dam Removal
2) Assessing the influence of climate change on the resources of the Olympic Coast National Marine Sanctuary
3) Evaluating the impact of debris from the Tohoku tsunami on the shorelines of the Olympic Peninsula