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The Seduction of Subduction

The views expressed are those of the author and are not necessarily those of Scientific American.


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This:

The Cascade Mountains

The Cascade Mountains

This is why I love the word subduction.  Every time I’m reading about the geology of a region, when I come across that word, I get a tingle down ye olde spine.  Because I know we’re in for it.  I know the landscape’s going to be exciting.  I know we’re in for volcanoes and earthquakes and some really wild metamorphism, accretionary wedges and the whole shebang.  It’s all there.  Tell me we’ve got a subduction zone on our hands, and you’ll see me bounce like a Jack Russell terrier who’s just eaten its owner’s entire stock of No Doz and chased it down with a case of Full Throttle.

In a subduction zone, you get some really wild rocks, rocks that’ve been through it, rocks that have been chewed up and spit out, rocks that, were they a letter, would get the post office in deep trouble for the amount of folding, spindling and mutilating they’ve endured.

Migmatite on the banks of the Skykomish River near Gold Bar, WA

Migmatite on the banks of the Skykomish River near Gold Bar, WA

A subduction zone takes your basic rocks and makes them sublime.  It pushes them down and raises them up.  It takes bits of the seafloor and chucks them up on land.

Pillow basalt on Marys Peak, Oregon

Pillow basalt on Marys Peak, Oregon

It takes your basic quiet marine shales, which had been resting peacefully in nice horizontal layers on the sea bed, and squeezes and cooks them into phyllite.  And then it hoists them high, standing them on end, and makes mountains of them.

Phyllite, Olympic Mountains

Phyllite, Olympic Mountains

Right now, right beneath me, the Juan de Fuca plate is subducting beneath the North American continent.  That subduction is the reason I’ve got land to sit on: over millions of years, subduction zone after subduction zone has formed around here, as oceanic plates meet continental, and as the seafloor goes down, bits of island arcs and seafloor sediments and appreciable chunks of the seafloor itself have gotten plastered on, creating the majority of Washington state, and the mountains that lured me here.  It’s a dangerous place to live.  This beauty does come with risk: chains of violent volcanoes, the certainty of an eventual megathrust earthquake.  But it’s worth the risk.

I’ve been seduced by subduction.  Looking at the result, who wouldn’t be?

Olympic Mountains sunset.

Olympic Mountains sunset.

A version of this post was originally published at En Tequila Es Verdad.

Dana Hunter About the Author: Dana Hunter is a science blogger, SF writer, and geology addict whose home away from SciAm is En Tequila Es Verdad. Follow her on Twitter: @dhunterauthor. Follow on Twitter @dhunterauthor.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. bucketofsquid 11:04 am 10/4/2013

    Wouldn’t it be cool if we had satellites in place for the last million years and could watch plate tectonics in high speed motion where 1 century took 1 second?

    Link to this

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