All juiced up

The cone’s profile was obtained with an 18 kHz depth sounder aboard CCGS John P Tully. The blue stem shows the 700-metre-long volcanic plume. Image courtesy Canadian Geological Survey
The cone’s profile was obtained with an 18 kHz depth sounder aboard CCGS John P Tully. The blue stem shows the 700-metre-long volcanic plume. Image courtesy Canadian Geological Survey

An active volcanic cone is venting large amounts of gas one kilometre beneath the swelling ocean of Duu Guusd the west coast of Haida Gwaii.

On September 28 scientists announced their discovery of the calcium carbonate encrusted mound, located 123 kilometres northeast of SGaan Kinghlas. They came across it during an expedition to explore the Queen Charlotte-Fairweather fault system that runs from Vancouver Island to Southeast Alaska.

The cone stands in a volcanic field with gas plumes bursting 700 metres high from multiple vents. The absence of fresh lava suggests it’s a mud-volcano.

“We think its methane,” speculated team-member and marine geologist. Dr H Gary Greene. “The reason for that is because of the chemosynthetic communities living around it. Clams and worms live off of bacteria that convert sulphides into energy. This is associated with methane seep.” The jets of methane would also explain the calcium-carbonate deposits that carpet the area. The seeping gas could be from buried and deteriorating organic matter or from a mantel source.

Scientists describe the surrounding marine-life as exotic and unusual. Because the community lives in complete darkness, it depends on ‘chemosynthesis’, meaning it derives energy from chemical sources, whereas terrestrial communities are based on ‘photosynthesis’, meaning they make energy from sunlight. The community includes thin-shelled mussels, 18-inch-long tubeworms, and clusters of iron-rich clams called Calyptogena elongota. Other clams that have been collected are harder to identify, and the teams will need to consult experts to confirm they haven’t come across undiscovered species.

The volcanic field is full of deep sea geological features, including tall calcium-carbonate chimneys and vast landslides reaching along the muddy bottom. Seismic readings suggest there may also be many other volcanic cones in the area. In fact, it now appears that the entire fault-system is scattered with volcanic centres. The expedition found that the region separating the North American Plate from the Pacific Plate is actively leaking gas and fluids.

“The whole fault-zone is juiced up,” Dr Greene explained. “Perhaps it’s from a heat force deep in the earth, we don’t know. This is all kind of new. There is a lot of speculation going on right now because there is so much fluid flow along this fault.”

The international team that made the discovery originally set forth aboard CCGS John P Tully to determine the slip-rate of the Pacific Plate. That calculation will help seismologists predict the size, likelihood and hazards of seismic activity.

When they found the volcano, a robotic submersible took photos and samples of the area. After analysis of this material marine geologists will be able to gauge the volcano’s activity and understand its origin. Scientists plan to return to the region to create high-resolution images of the area and to take further samples.

The volcano is located at 54°08’34.8”N 134°28’30.7”W, 123 km north-east of SGaan Kinghlas Bowie Seamount and 91 km west of K’iis Gwaay Langara Island.

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