An ancient puzzle called the "ghost forest," in Washington State's coastal region of the Copalis River, was originally "solved" by theorizing that a slow salt-water inundation, from gradual subsidence, had killed the cedar trees. Then, the trees were ring dated, and it was discovered they'd all died in the winter of 1699: no leisurely geologic process involved. This discovery was linked to a dawning scientific awareness of an unsuspected source of earthquakes: subduction zone slippage. The ghost forest sits in the middle of the historically dormant Cascadia Subduction Zone. The written history of the region begins after 1700, the time of the tree deaths, but the oral history has tales of catastrophe: the annihilation of tribes living in the Vancouver and Oregon regions, by sudden floods. On the other side of the Pacific, in Japan, there were written, dated records of an orphan tsunami: a great wave associated with no known earthquake. The orphan tsunami was linked to the ghost forest and it was realized a magnitude-9 earthquake had hit the Vancouver/Oregon area in 1700. Using the Japanese history, and allowing for the propagation of the wave across the Pacific, scientists were able to pinpoint the time of the earthquake remembered in tribal traditions to, January 26, 1700, at 9:00 p. m. The picture above links to Discover Magazine's account of the solving of this mystery.
Nine years prior to the Discover Magazine article, the National Geographic publicized the scientific evidence and growing concern in the linked article. Recently, attention to the inevitability of the next big quake in the region was stimulated by the devastating tsunami in Japan, in 2011. Communities Digital News, did a story in 2014. The article emphasizes the destructive potential and discusses survival policy. The Incorporated Research Institutions for Seismology have an essay on the subject, including a video of the subduction process.
The Cascadia Subduction Zone is a story whose time has arrived, as witness this recent treatment by Earth Magazine. The above picture links to an article on the subject by the Pacific Northwest Seismic Network. GeekWire also recently summarized the whole thing. There is even a spinoff effect into popular culture, evidenced by this literary magazine: The Cascadia Subduction Zone. Finally, The New Yorker magazine recently published a long article recounting the whole story, emphasizing the need to be afraid, very afraid.
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