Over one thousand years ago, a volcano erupted on the Yukon-Alaska border leaving behind White River Ash on a massive area of the region. However, a recent studyshows that the affected area may have been even larger.
The eruption in question took place in 850 AD at Mount Churchill in southeastern Alaska. The original theory was the ash produced by that eruption covered 1,000 kilometers, however, researchers have now found that the area is far more expansive.
Geoscientist Britta Jensen is the lead author of the study “Transatlantic distribution of the Alaska White River Ash.” She has worked in Canada and Alaska for many years and says she came upon the White River Ash topic by accident.
“Few years ago, we went to the American Geophysical Union fall meeting, and I saw a talk by someone who had been working in Europe and they had just done a project in Newfoundland on the east coast of Canada and they had found these microscopic beds of ash. And he found that they actually had records of quite a few ash beds in Newfoundland, which was a bit surprising for us because we didn’t expect that that many would travel that far. And they were having trouble identifying them because they were coming over from Europe and they didn’t really know our local records and it looked like everything that was going to Newfoundland was coming from the West.”
Jensen says the researchers began comparing samples of the White River Ash to see if the samples found in Newfoundland matched those in Alaska-- they did. The samples also matched some ash beds in Europe. She says they found White River ash particles as far as 7,000 kilometers away from the volcano.
Geologists use volcanic ash beds and geological records for two things.
“One is that every volcanic ash that erupts because the dynamics in the magna chamber in a volcano are so varied that every time it erupts the chemical composition of the ash is unique. So we can actually chemically finger print an ash bed and once we’ve chemically finger printed an ash bed we can identify it where ever we find it. And if we know how old the ash bed that means we can tell how old whatever we are looking at is, whether it’s dirt or some kind of climate record. We use these ash beds to essentially date our geological sequences and then also to correlate them to one another.”
However, Jensen says the public at large can learn more about the hazards of volcanoes from this new study. She says if a volcano erupted ash today at the same level as the one she studied, there would be massive consequences that didn’t exist in 850 AD.
“For people who are close to the volcanoes, the ash is mostly glass. So it’s very dangerous in terms of inhalation, it’s bad for your lungs obviously you don’t want to inhale glass shards, and it’s bad for any infrastructure. Once it gets into the sky, it’s a hazard to jet planes because the jet engines can suck the ash in and what happens is the jet engines are really hot and it can actually melt it again and then it refreezes in the engine and it can cut them out.”
The Icelandic ash cloud in 2010 cost the aviation industry $7.3 billion in damages and lost revenues. That eruption closed European airspace for five days was smaller than the ash spread that Jansen studied. Eruptions like the one that produced White River ash occur once every 100 years on average and could cause massive damage to global air travel.