Saturday 19 January 2013

Don't Blame Canada! Events In Northwestern North America Cast A Long Shadow In Mid-Ninth Century C.E. Europe

This just in. Well, that is, it was 'just in' about 1,250 years ago. And not here. Europe. Well, here and there. By 'here' I mean... maybe a pitcher or two'll tell the story better. First, there was this on Facebook, from our friend Breck Parkman.

That led me to the 'official' announcement, from the University of Alaska Fairbanks Geophysical Institute: "White River ash made its way across the globe." Ash dated to about 860 C.E. has been recovered in places across northern Europe. However, its origin was an enigma until now. Britta Jensen and Duane Froese (University of Alberta) have apparently solved a long-standing mystery of European geology.
The White River Ash blasted from giant eruptions somewhere in today’s Wrangell-St. Elias Mountains, drifted as far away as Ireland and Germany, said experts who attended the December 2012 Fall Meeting of the American Geophysical Union, held in San Francisco.
Near the source, the ash-fall was impressive, as the photo below illustrates.

PHOTO CAPTION/CREDIT: Duane Froese of the University of Alberta in a forest of stumps smothered by the White River Ash around the year 843 AD. Froese is pictured in the Yukon Territory, close to the Alaska border and Natazhat Glacier in an area downwind of the great White River eruptions, which spewed from somewhere near Alaska’s Mount Churchill. Photo courtesy of D. Froese. 

The Wrangell--St. Elias Mountains lie in southern Alaska. As you can see from the Google earth graphic below, they're almost half a world away from Ireland and Germany.

As for the topographic character of the present-day place of origin, the image below gives some idea of the 'bowl' presumed to be the remnant of the enormous explosions of ash. Mounts Churchill and Bona are indicated. It's possible to see the huge snow-free scarp immediately downslope, and another, nearer the bottom of the photo, evincing another large, arcuate head scarp.

For scale, the two peaks are 4.14 km apart. Vertical scale exaggerated 1:2. (Source: Google earth.)
One can imagine that, in places where it occurs archaeologically, the White River ash may be a useful time-marker. Especially when you remember that at this time in its history, in places across Europe, there was at best a sparse written record, and ceramic and other relative dating techniques might not yield precise temporal information.

Catch you next time!

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