Tsunami

Devastating waves called tsunamis can strike Oregon’s coast at any time. These giant waves are caused by great undersea earthquakes, which can occur along the Cascadia Subduction Zone, one of the largest active faults in North America. The fault zone lies 32 to 70 miles offshore and roughly parallels the coast. Cascadia tsunamis have struck the Oregon coast several times in the past 2,000 years. Most recently, about A.D. 1700, a tsunami caused by an earthquake on the Cascadia Subduction Zone flooded beaches, tidal channels, and marshes up to one mile inland from Seaside's present-day boardwalk. Tsunami-deposited sand found in Seaside and other coastal lowlands in Oregon, Washington, British Columbia, and northernmost California shows that this tsunami and earlier ones affected large areas.

Seaside, Oregon · United States