Friday, October 14, 2016

Scientists investigate discovery of fumaroles atop Mount Meager, a dormant volcano near Pemberton

Larry Pynn
Vancouver Sun
October 7, 2016

For video:
Is a dormant volcano near Pemberton BC ready to blow?

Volcanologist Melanie Kelman with Natural Resources Canada is taking a closer look at Mount Meager, north of Pemberton, after a discovery this summer showed the long-dormant volcano is a little more active than originally thought.
Scientists are investigating the “new and interesting” discovery of a fumarole field atop Mount Meager, a dormant volcano near Pemberton that is expected to blow its top one day and pose a threat to people and property in the region.

Melanie Kelman, a volcanologist with Natural Resources Canada, said in an interview that a helicopter pilot with a geological background reported seeing fumarole activity this summer at Mount Meager.

Based on the report, volcanologists Kelly Russell of the University of B.C. and Glyn Williams-Jones of Simon Fraser University visited the site twice and took measurements. They discovered steam, carbon dioxide and hydrogen sulphide, but not sulphur dioxide, which could have indicated the presence of magma and a potential eruption. There’s been nothing to suggest unusual earthquake activity in the area.

“It would take a lot of work to bring magma to the surface,” Kelman said. “We’d expect to see hundreds or thousands of small earthquakes and we’re not seeing that. We don’t think an eruption is imminent. We think this is a new and interesting discovery of a fumarole field.”

She noted that hydrogen sulphide can be toxic at close range — a warning against anyone thinking of visiting the fumaroles. “Anyone who attempts to approach or enter the fumaroles could die. The ice is also very unstable around them.”

Fumaroles are gas vents in the earth’s surface, and these ones measure up to 20 metres deep and 30 metres in diameter. There have been reports of sulphur smells downwind of that area for some 40 years, which suggests the fumaroles are long-lived features.

Kelman said the most likely scenario is that thinning of ice atop Mount Meager exposed the fumaroles, potentially as a result of climate change. Another scenario is that the fumaroles became hotter over time and chewed their way through the ice. Others may exist just below the ice surface.

A new seismic station has been installed at Mount Meager to better monitor for small earthquakes. And special satellite-based technology — interferometric synthetic aperture radar — will also be used to detect any movement in the surface that could indicate activity.

Canada’s last major explosive eruption occurred at Mount Meager northwest of Pemberton about 2,360 years ago, a blast on par with the explosion of Mount St. Helens in Washington state in 1980. Mount Baker, just south of the Canada-U. S. border, also has fumaroles.

It’s unknown when Mount Meager might erupt again, posing a potential threat within a radius of tens of kilometres. “The big thing is it’s been a long time since the last eruption and we don’t know when the next one will be,” Kelman said. “It could be in 50 years or 3,000. I still consider the volcano dormant.”

In 1975 four members of a geophysical survey crew were buried by a debris torrent that swept down Devastation Creek, evidence of the area’s unstable volcanic rock. In 1990 a similar event stranded visitors to Meager Creek hotsprings.

Individual volcanoes can be considered extinct when they have exhibited no activity for 10,000 or more years, even as their larger volcanic belts remain active. Mount Meager is part of the Garibaldi belt.

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