12 new volcanoes discovered in Southeast Alaska

June 1, 2013 – ALASKA – In Alaska, scores of volcanoes and strange lava flows have escaped scrutiny for decades, shrouded by lush forests and hidden under bobbing coastlines. In the past three years, 12 new volcanoes have been discovered in Southeast Alaska, and 25 known volcanic vents and lava flows re-evaluated, thanks to dogged work by geologists with the U.S. Geological Survey (USGS) and the U.S. Forest Service. Sprinkled across hundreds of islands and fjords, most of the volcanic piles are tiny cones compared to the super-duper stratovolcanoes that parade off to the west, in the Aleutian Range. But the Southeast’s volcanoes are in a class by themselves, the researchers found. A chemical signature in the lava flows links them to a massive volcanic field in Canada. Unusual patterns in the lava also point to eruptions under, over and alongside glaciers, which could help scientists pinpoint the size of Alaska’s mountain glaciers during past climate swings. Now comes the CSI twist. All of these newly tested lavas in Alaska are kissing cousins to volcanoes in Canada, such as Mount Edziza, which last erupted about 10,000 years ago. The connection makes perfect sense, Karl said. “I’m actually surprised no one has hypothesized it before,” she said. “It made total sense that this volcanic province would extend across Southeast Alaska, and now I have the data to show that’s the case.” Little known outside of Canada, Mount Edziza is part of the Northern Cordilleran Volcanic Province, a broad swath of volcanoes and hot springs some 1,250 miles (2,000 km) long and about 375 miles (600 km) wide. Karl’s big picture meets approval with scientists studying Canada’s volcanoes. “I knew there were volcanic structures to the west in Alaska, but I didn’t know they were nearly [this] extensive,” said Ben Edwards, a volcanologist at Dickinson College in Pennsylvania, who is not involved in the project but has visited the new volcanoes with Karl and Baichtal. “They have really found a lot more places than we realized, but there’s certainly no reason for them not to be there. It makes a lot of sense.” The tortured history of this corner of North America, a legacy of collision between the North America and Pacific tectonic plates, created a meshwork of leaky faults and fractures. Magma escapes from Earth’s mantle through this patchwork when forces pull on the crust, opening space. The matching chemistry also hints that magma in both regions comes from a similar mantle source. 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. 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. –Live Science

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