Opus Tsunami - The Next Big One

Where will the next big tsunami strike? The answer is terrifying. From my book "Opus Tsunami," free for all subscribers of The Drescher Drop

Where will the next big tsunami strike? The odds are strongly in favor of one spot in particular: the Cascadia Subduction Zone off the coast of northwest Canada and the USA. 

This is another subduction zone in the Ring of Fire, where the Juan de Fuca plate is constantly sliding under the North America plate. The entire zone covers hundreds of miles off the Pacific coast of North America, from the Queen Charlotte Islands (Haida Gwaii), along Vancouver Island and heading south past Seattle, Portland, and ending just north of San Francisco. 

According to the Pacific Northwest Seismic Network, the Cascadia Subduction Zone

…may be unique among the worlds subduction zones in that it produces very few (if any) earthquakes unambiguously on the plate interface. Coupled with evident occurrence of great megathrust earthquakes, the CSZ must be much more strongly locked than other subduction faults. (National Weather Service)

Geologists know it will happen. The only question is “When?” To find out, researchers looked back in the natural history of the Pacific Northwest, and what they discovered is a warning. First, they discovered preserved tree trunks under the mud just off the coast. Large parts of the seabed all along the zone used to be above the water and were covered in forest. At some point, it sank beneath the ocean, much like how the coast of Japan sank in 2011. Through analysis of the tree rings, researchers put the date of the event at some point after 1699.

Then, along the Copalis River, geologists discovered a layer of ocean sand that had been deposited miles from the coast. Evidence of the sudden destruction of trees and the quick deposit of silt showed a massive tsunami had reached far inland. Once again researchers were able to ascertain a date of just after 1699.

In fact, all along the Pacific Northwest coastline, there’s evidence of a sudden coastal drop and a massive tsunami that reached at least 16-feet high. But the clincher in the argument came from far away, on the other side of the Pacific.

The Japanese have been keeping detailed records of events on their islands since at least 600 CE (Common Era, or AD). Among these records are numerous accounts of various tsunamis, including one particularly destructive wave which hit in January 1700. There were no reports of an earthquake in Japan, and the tsunami seems to have taken the islands by surprise. It reared up out of nowhere, having traveled from a long way away. 

Put together, researchers unanimously agree that in early 1700 the Cascadia subduction zone experienced a massive megathrust earthquake, which destroyed thousands of miles of coastline and sent a devastating tsunami racing across the Pacific Ocean. Tales from the local native inhabitants speak of a terrible earthquake and tsunami all up and down the coast.

In Northern California, in 1700, the Yurok people gathered on high hills and looked down as the ocean swallowed their village and the forests below them. Much further north, the Nuu-cha-nulth of British Columbia speaks of a Thunderbird and a Whale fighting so much that the earth shook violently, and then the ocean flooded in and took their homes and their children and their canoes. The date of this event is January 1700.