An earthquake written in wood
At low tide on the Oregon coast, the remnants of an ancient forest appear on the beach. These barnacle-covered stumps belong to Sitka spruce (Picea sitchensis) trees, some of which are 2,000 years old. They are evidence of a massive geological event that reshaped this coastline centuries ago. The stumps, once 150- to 200-foot-tall trees, were preserved in sand and mud after the forest was abruptly submerged in salt water.
This "ghost forest" was created by the Cascadia Subduction Zone, a 700-mile-long fault that runs from Northern California to Vancouver Island. On the evening of January 26, 1700, this fault ruptured, causing a megathrust earthquake with an estimated magnitude of 8.7–9.2. The quake caused the coastline to suddenly drop by as much as two meters, plunging the forest into the tidal zone. The saltwater killed the trees, but the oxygen-poor mud preserved their stumps, which were hidden under the sand for centuries until storms in 1997–1998 exposed them.
A story told across the ocean
The exact date of this earthquake was determined through a combination of geology and historical records from two continents. Scientists used dendrochronology, or tree-ring dating, on the ghost forest trees. The analysis showed the trees had formed their last growth ring in the summer of 1699, meaning they died sometime between the fall of 1699 and the spring of 1700.
Across the Pacific, historians in Japan had long known of an "orphan tsunami" that struck their coast on January 27-28, 1700, without any preceding earthquake. By calculating the tsunami's travel time across the ocean, approximately nine to ten hours—researchers pinpointed the earthquake's occurrence to around 9:00 PM Pacific time on January 26, 1700. The geological data aligned with the centuries-old oral traditions of Pacific Northwest indigenous peoples. Stories from the Huu-ay-aht, Quileute, and other nations describe a terrifying, ground-shaking night and a massive wave that swept away entire villages. These accounts, passed down through generations, described the 1700 Cascadia event accurately long before the scientific evidence was assembled.