Anniversary of 1700 Quake a Spooky Reminder of What's Coming to Oregon, Washington Coast

Published 01/27/21 at 4:26 AM PDT
By Oregon Coast Beach Connection staff

(Seaside, Oregon) – While it's not an anniversary to celebrate, it is definitely one of note – and caution. With Tuesday having been the 321-year anniversary of the 1700 Cascadia magnitude 9.0 quake, it is a stark reminder of what damage such an earthquake can inflict on a region. (Above: the 1964 tsunami in Seaside came from an earthquake in Alaska. Photo courtesy Tom Horning).

The quake happened in the morning hours of January 26, 1700, off the Oregon and Washington coast, resulting in a tsunami about 25 feet high along stretches of beach from California to British Columbia, as well as wreaking devastation in Japan. The center of it was the Cascadia Subduction Zone, a faultline that stretches from northern California to B.C., created by an area where two continental plates meet.

And it's all part of something geologists expect again, likely within the next 50 years. Estimates from OSU geologists, including Dr. Chris Goldfinger, are that there's a 40 percent chance of another such eruption off the Oregon and Washington coasts in the next 50 years. The devastation will be enormous, and depending on where the slip of the faultline happens it could affect Portland and Seattle as much as their coastal regions.

The 1700 earthquake and its tsunamis occurred with such force because this is where the Juan de Fuca Plate is sliding underneath the North American Plate.

Seaside, Oregon geologist Tom Horning has long studied this region.

“When it breaks, we will have a M9 quake and the killer tsunami,” he told Oregon Coast Beach Connection.

Horning – like many other geologists – say the next biggie is quite possibly overdue.

“We are in a cluster of quakes and tsunamis that have occurred every 330 years, on average. Next one may be around the corner. Six of the past 21 Cascadia events occurred before 300 years had passed since the previous wave. The next wave may be as high as 55 ft.”

It's a spooky scenario that numerous scientists noted Tuesday, as well as government officials. Oregon officials also said the COVID pandemic proved Oregonians are not ready for the big one, pointing to the rushes for some products in the spring. Officials say you need to have two weeks of supplies for such an emergency (see the State of Oregon's preparedness page).

In the coming large-scale quake, Horning said Seaside would be covered in 10 to 40 feet of water. Bridges would be destroyed immediately, cutting off hundreds if not more from evacuating beyond the Necanicum River. All those souls would be swallowed up, a number Horning predicted could be anywhere from 1000 people to 20,000.

Horning, who sits on the Seaside city council, has been pushing for bridge upgrades for years now, funded by local hotel taxes. The idea hasn't gone far.

Portland is in the middle of a similar morass, with many pushing to get Bridgetown a bit more earthquake proof.

What did not happen with the 1700 tsunami is almost as interesting as what did happen. One thing the Cascadia tsunami did not do is create the Neskowin ghost forest, or any other ghost forests found on the beaches of the Oregon coast. That is a different origin, and the forest's carbon dating of 2000 years disproves that theory.

The 1700 tsunami did, however, create many other ghost forests inland, in just about every estuary on the Oregon coastline. They're not very obvious, however, and more often resemble regular stumps. The tsunami left a sizable ghost forest of stumps near Copalis, Washington, as well. More photos below:

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Above: more photos of the 1964 tsunami damage in Seaside

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