New Volcanoes Discovered in Alaska|Volcanoes

Behm Canal underwater volcano, Alaska — One of the newest volcanic vents discovered in Southeast Alaska is an underwater volcanic cone in Behm Canal near New Eddystone rock.

(Image 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.

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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.

"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."

As in Canada's volcanic province, Southeast Alaska's volcanoes and hot springs line up as amazingly linear features. Here's why: 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.

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.

Becky Oskin covers Earth science, climate change and space, as well as general science topics. Becky was a science reporter at Live Science and The Pasadena Star-News; she has freelanced for New Scientist and the American Institute of Physics. She earned a master's degree in geology from Caltech, a bachelor's degree from Washington State University, and a graduate certificate in science writing from the University of California, Santa Cruz.