Volcanoes and climate change
While the volcanoes in Canada and Alaska have erupted for more than 10 million years, emerging data suggests that the last 3 million years of glaciers growing and retreating in Alaska and British Columbia also prompted many small volcanoes to erupt, because the changing ice mass flexed the Earth. This activated the fractures and made room for more magma to rise.
In Tolay Regional Park, north of Mount Edziza, Edwards is assembling evidence of periodic eruption pulses in the last 2.5 million years.
"We don't have a lot of the information yet, but it's consistent with some sort of link between glaciations and volcanism. If you put 2 to 3 km [1.2 to 1.8 miles] of ice on that part of the cordillera and then remove it pretty quickly, it may facilitate extension," he said.
The molten rock also has preserved impressions of bygone glaciers. Many of the lava flows touched ice, leaving a distinctive cooling pattern in the chilled rock. By dating the glacially cooled lava flows, researchers such as Karl, Baichtal and Edwards hope to better understand how much land mountain glaciers covered during past glaciations. About one-third of global sea level rise could come from melting mountain glaciers, but estimating their past size is difficult because growing glaciers plow through evidence of their predecessors.
Risk of eruptions
Despite its great size, the overall risk from eruptions in the Alaska portion of the volcanic province is low, Karl said.
In Canada, the volume of erupted lava is less than 240 cubic miles (100 cubic km) every million years in the last 2 million years. By comparison, Hawaii's Kilauea volcano spewed 4,650 cubic miles (19,400 cubic km) in the past 300,000 to 600,000 years. (Big Blasts: History's 10 Most Destructive Volcanoes)
The most recent eruption in both countries was at the Blue River lava flow in Lava Fork, which crossed the Alaska-Canada border 120 years ago, according to new dating work by Karl and her colleagues.
"Even though, theoretically, a volcano that erupted 120 years ago is an active volcano, but because it's so remote there isn't any real concern about it," Karl said.
However, an eruption in 1775 killed a village of First Nations people in Canada, though scientists aren't sure why. Lava didn't reach the town, and some researchers suspect gas from the volcano may have suffocated residents.
Karl notes that an earthquake on the Fairweather Fault, a major offshore strike-slip fault, presents a greater risk than a volcanic eruption. "If something is rumbling and bubbling we have so much more technology to become aware of it before it's a hazard, We can't predict exactly when the Fairweather Fault is going to go, and that's a much larger hazard," she said.
With 15,000 miles of shoreline and hundreds and hundreds of islands to explore, Karl and Baichtal think there are more volcanoes to discover in Southeast Alaska.
"It's a tough place to get around, but Sue and I just laugh at it. We will never finish," Baichtal said.
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