Up and down the coast of Oregon and Washington USA there are forests that appear only at low tide. They rise from the waves in eerie silence, each tree a crumbling reminder of its former glory. These are the Ghost Forests and they are leftover from the last Cascadia Megathrust earthquake.
The Forest Before
If you live on the west coast of Canada (or the US – Hi neighbour!) than you’ve likely walked through a spruce forest before. Trees reach 45-60 meters (150-200 feet) tall, spearing the sky with needled branches and littering the ground with pine cones (spruce cones?).
The Neskowin trees were around 200 years old when the last megathrust earthquake hit north America. They were also above sea level.
What Happened?
2000-ish Years ago the west coast shook with a Cascadia Megathrust earthquake. This would have been similar to ‘The Big One’ that many anticipate happening in the next 50 years or so near BC. Scientists believe that the shoreline dropped with the force of the event, dumping the forest below sea level.
Either landslides or a tsunami wave followed the earthquake, burying the bottoms of the trees in debris. This preserved them and kept them hidden until 1997-1998 when unseasonably severe storms swept away the covering layer. Since then, we’ve been able to study the trees to learn more about earthquakes in our region.
How do we know?
Original studies led researchers to believe that the trees died slowly as changes in sea levels covered the roots. Salt would have poisoned the trees, killing them over time as the waves encroached. This was later disproved when the original soil (still present at the base of the trees) was shown to have been buried suddenly. Geologist believe that this was caused by a major and abrupt event like an earthquake.
For those of us that did not pay attention in grade 10 science, carbon dating uses the known lifespan of chemicals to figure out the age of an object. Through this method geologists were able to date the trees time of burial, and through rings could estimate the age of the trees when buried.
Other Effects of the Cascadia Megathrust
The earthquake that created this ghostly spectacle was likely either a 8.4M or an 8.6M. These quakes occurred relatively close together (in geological time). While I was unable to find research on these specific quakes, there is a more recent, similar event that we can use to draw some likely assumptions.*
Back in January 26, 1700 there was an estimated 8.7 – 9.2M megathrust earthquake along our coast. The average slip along the 1000 km of fault effected was 20 meters. These quakes caused Ghost Forests of their own in Oregan and Washington. Oral histories of First Nations peoples also show that several communities were evacuated, and others wiped out around this time.
*I am not a scientist, take this with a grain of salt.
Prepared, Not Scared
Although historically these massive earthquakes occur every 500 years or so, there is only a 1 in 3 chance that it will happen again in the next 50 years. That’s a 2 in 3 chance that it won’t.
At Quake Kit we stand with others in our industry in a Prepared, Not Scared approach. Our goal is to educate our readers about the scope of the potential risks our West Coast might face, and to show what can be done to minimize the risk. Some readers may find the above information unsettling, but rest assured, as long as we make a plan, educate ourselves, and keep a comprehensive and up to date emergency kit, our odds of surviving a major event are very high.
If you have any questions or comments on the above please let us know in the comments – we’d love to hear from you!
This article was written by Zenia Platten – Writer and Emergency Preparedness professional. Want to read more of Zenia’s work? Check out her new book, Tethered, currently available for pre-order through Kindle, Nook, and Kobo.