Along the coasts of Oregon and Washington, in the United States, the gray skeletons of thousands of western redcedars known as the ghost forests rise from the marshes. For generations, people believed these trees had died gradually due to environmental changes. However, in the 1980s, geologist Brian Atwater discovered a tectonic catastrophe etched suddenly into the underground strata.
While excavating estuarine mud, Atwater found that the roots were anchored in an ancient forest soil layer instantly buried beneath marine sand brought in by giant waves. The geological explanation was startling: the Cascadia subduction zone, where the Juan de Fuca plate slides beneath the North American plate, had accumulated centuries of elastic friction before suddenly rupturing, causing the coastal strip to drop one to two meters in mere seconds, drowning the forests in saltwater.
To find out exactly when the disaster struck, science connected two fascinating clues:
- Dendrochronology: The study of the growth rings in the tree trunks revealed that all the trees died at the same time during their dormant phase, between late autumn 1699 and spring 1700.
- Japan's 'orphan tsunami': Japanese port records from the Edo period documented a mysterious and destructive giant wave in January 1700, with no earthquake felt in the islands.
Cross-referencing the data confirmed the exact time: on the night of January 26, 1700, a colossal magnitude 9.0 earthquake struck, forever transforming the region's geography.
Source: United States Geological Survey (USGS) - The Orphan Tsunami of 1700 (Brian F. Atwater et al.)
