Mount St. Helens, diamtoms, and North American volcano eruptions of the past 11,000 years. With images fromTodd Kristensen, Dr. Alex Wolfe and Dr. Will Hobbs, Austin Post (USGS).
Researchers have recently found evidence that North America's ancient volcanic eruptions not only dwarf those from modern times, but happened more often than you’d think. Should paleohistory repeat itself, will Canada be ready?
Without a single active volcano in the province, perhaps Albertans can be forgiven for not having an eruption response plan. It may be hard for residents to believe that the province's largest environmental catastrophe in the human era was a volcanic ash fall. Approximately 7,600 years ago, the skies were blackened for weeks in southern Alberta as more than 10 centimetres of ash descended on the prairies. The airborne debris came from what is now Oregon, when 100 cubic kilometres of ash spewed from Mount Mazama. Crater Lake now occupies the site of the eruption, which makes modern disasters look like a sneeze: The 1980 eruption of Mt. St. Helens in next-door Washington State ejected just two km3 of ash, and the Icelandic eruption of Eyjafjallajökull in 2010 (which cost the airline industry more than 900 million euros in six days) ejected barely 0.25 km3.
Massive explosive force propelled Mazama ash high into the atmosphere, where winds spread it over a vast area east and northeast. It took an estimated 12 hours for the wall of ash to reach Alberta; then the “dry snow” fell for days. The ash fouled drinking water, killed food plants and left smothered forests susceptible to wildfires and mudslides. Archaeologist Gerald Oetelaar of the University of Calgary has found evidence that many human-occupied landscapes across the province were abandoned at this time.
Today, few Canadians are aware of the magnitude of this event or the frequency of past volcanic eruptions. Yet research into our paleo past suggests we may wish to consider its lessons for the present, as climate disruption threatens the habitability of some heavily populated areas. While governments might be unable to deal with a one-in-10,000-year ash blanket across the continent, could better briefings from paleoscientists prepare us for smaller but more frequent disasters such as megafloods, droughts and lesser eruptions? With 67 smaller volcanic eruptions in North America in the past 100 years, it’s worth girding for higher-probability, geologically modest but still serious events.
It often takes direct experience of a large-scale catastrophe to make us prepare for the next one. Volcanologist Catherine Hickson finds there is a window of just nine months to a year following a major disaster to enact change before public interest and political motivation fade. The current fabric of urban society, with large fixed populations and vulnerable infrastructure, combined with the short-term perspectives of modern politics, may in fact be weakening our resilience to large-scale disasters.
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