December 14, 2005
Cascadia's Sword of Damocles
One of the wonderful things about living in Cascadia is the sense that the earth beneath our feet is very much alive. This is a land of volcanoes, hotsprings, and earthquakes--a place where geology is no distant abstraction. Even the region's name, Cascadia, is shared with a large subduction zone in the north Pacific where one continental shelf is sliding beneath another.
Yet in spite of everything, and apart from a few expensive seismic retrofits and construction projects, we Cascadians are pretty glib about our potentially catastrophic footing. But we can live in tranquil ignorance no longer: a fascinating new book blends history and geography to tell the story of a tsunami that struck Japan in 1700. The cause? A huge earthquake in Cascadia--estimated between a magnitude 8.7 and 9.2--that sent floods rippling across the Pacific.
We're all too familiar with the horrifying effects of big earthquakes--the Southeast Asian tsunami and the recent earthquake in Pakistan. But what would happen if a similar sized quake struck again in Cascadia? And what lessons can we learn from the history of the Northwest before it was inhabited by Europeans? Well, I've just now cracked the cover but I'm about to find out. And if you're looking for a Christmas gift for a geeky naturalist type, check out The Orphan Tsunami of 1700.
Posted by Eric de Place | Permalink
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I recently heard a lecture on that from a dendrochronologist. Enough of the shoreline dropped that they can still find reefs of dead stumps below cliffs with pre-1700 forests on them; and by comparing the ring patterns of the stumps with the ones on living trees, they can date the subsidence to not only a year but a season.
Lovely corroboration of the Japanese records of the orphan tsunami, but yes, it should frighten anyone living here more than it does me.
Posted by: clew | Dec 15, 2005 11:12:34 AM