Graham Hill of GNS Science, an earth and nuclear science institute in Wellington, New Zealand, led a team that set up magnetotelluric sensors around Mount St Helens in Washington state, which erupted with force in 1980. The measurements revealed a column of conductive material that extends downward from the volcano. About 15 kilometres below the surface, the relatively narrow column appears to connect to a much bigger zone of conductive material.Before you start freaking out over a molten apocalypse devouring the west coast, and go do something foolish like canceling your summer vacation, consider the requisite skeptic:
This larger zone was first identified in the 1980s by another magnetotelluric survey, and was found to extend all the way to beneath Mount Rainier 70 kilometres to the north-east, and Mount Adams 50 kilometres to the east. It was thought to be a zone of wet sediment, water being a good electrical conductor.
However, since the new measurements show an apparent conduit connecting this conductive zone to Mount St Helens - which was undergoing a minor eruption of semi-molten material at the time the measurements were made - Hill and his colleagues now think the conductive material is more likely to be a semi-molten mixture. Its conductivity is not high enough for it to be pure magma, Hill says, so it is more likely to be a mixture of solid and molten rock.
Gary Egbert of Oregon State University in Corvallis, who is a magnetotellurics specialist but not a member of Hill's team, is cautious about the idea of a nascent supervolcano where Mount St Helens sits. "It seems likely that there's some partial melt down there," given that it is a volcanic area, he says. "But part of the conductivity is probably just water."Let's hope so. It's bad enough having one supervolcano within world-ending distance of the Pacific Northwest. No need for two.