A Blast of a Find: 12 New Alaskan Volcanoes
Becky Oskin, OurAmazingPlanet Staff Writer
Date: 31 May 2013 Time: 02:32 PM ET
 |
One of the newest volcanic vents discovered in Southeast Alaska is an underwater volcanic cone in Behm Canal near New Eddystone rock.
CREDIT: James Baichtal, U.S. Forest Service
|
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.
“It’s giving us this serendipitous window on the history of climate in Southeast Alaska for the last 1 million years,” said Susan Karl, a research geologist with the USGS in Anchorage and the project’s leader. [Image Gallery: Alaska's New Volcanoes]
Volcano forensics
The project kicked off in 2009 as part of an interdisciplinary effort to better understand volcanism in Southeast Alaska, Karl said.
The team’s first result, from a volcanic pile about 40 miles (70 kilometers) south of Mount Edgecumbe, was an intriguing match in time to the panhandle’s biggest volcano. The team planned to test if the two were related, sort of a geologic genetic test. But even though the two volcanoes had erupted at about the same time in the past, their chemistry was wildly different. It was like one volcano was a freshwater fish and the other came from the salty ocean. And what really captured the geologist’s attention were signs that the little volcano squeezed out lava that oozed next to glaciers.
“That’s when we realized we had a whole new kind of volcano separate from Mount Edgecumbe,” Karl told OurAmazingPlanet.
Lava chemistry holds forensic clues that reveal what was happening in Earth’s crust and mantle when the magma formed. The unusual chemistry sent Karl and her collaborators hunting for more rocks to test. This meant days-long backpacking trips into remote wilderness or submersible dives to underwater volcanoes.
Underwater volcanoes and cinder cones pockmark Behm Canal.
CREDIT: James Baichtal, U.S. Forest Service
Not only did they find the same unique chemical signature at other sites, the team stumbled upon new volcanoes overlooked by earlier mappers.
“We’re convinced now there’s probably a whole bunch of green knobs out there covered with timber that may be vents that may have never been mapped,” said James Baichtal, a geologist with the U.S. Forest Service based in Thorne Bay, Alaska, and a project leader.
Connection to Canada
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 volcanics 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.”
Read Full Article Here
Núi lửa Shiveluch (Ảnh: NASA)
