Alaska Science Forum: White River ash made its way across the globe
By nrozell [at] gi [dot] alaska [dot] edu (Ned Rozell)
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.
Ash from the White River eruptions, possibly from 15,638-foot Mount Churchill or at least close to it, left an easy-to-see mark on eastern Alaska and northwestern Canada. Explorer Frederick Schwatka documented the ash in 1885 in his book “Along Alaska’s Great River.” People driving the Klondike Highway pass more than two feet of the whitish grit exposed in road cuts on their journey through the Yukon Territory.
“It was an enormous eruption,” said Britta Jensen of the University of Alberta in Edmonton.
Jensen studies volcanic ash layers in northwest Canada and Alaska. Recently, she and Duane Froese, also of the University of Alberta, along with colleagues in the United Kingdom, connected the dots on some far-flung findings of old volcanic ash.
Froese and Jensen traveled in the Yukon to a branch of the upper White River, which flows from glaciers in Alaska and dumps into the Yukon River. There, they cored the grey trunks of spruce trees smothered by White River ash. Using radiocarbon dating, they found the trees died in the year 843 AD, give or take about 20 years.
Recently, U.K. researchers located an ash layer familiar throughout Europe that scientists first found in Ir