Mount St. Helens is a cold-hearted volcano | Science News

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How Bizarre

Mount St. Helens is a cold-hearted volcano

Scientists are still searching for the source of volcano’s heat

By
12:00pm, November 1, 2016
Mt. St. Helens

NOT HOT SEAT  While a volcano called Mt. Adams (background) is fed by an obvious heat source, Mount St. Helens (foreground) sits above a wedge of rock formed at the edge (or “cold nose”) of the North American tectonic plate.

Below most volcanoes, Earth packs some serious deep heat. Mount St. Helens is a standout exception, suggests a new study. Cold rock lurks under this active Washington volcano.

Using data from a seismic survey (that included setting off 23 explosions around the volcano), Steven Hansen, a geophysicist at the University of New Mexico, peeked 40 kilometers under Mount St. Helens. That’s where the Juan de Fuca tectonic plate releases fluids due to intense heat and pressure as it descends beneath the North American plate. Those fluids rise and trigger melting in the rock above, fueling an arc of volcanoes that line up like lights on a runway. All except for Mount St. Helens, which stands apart about 50 kilometers to the west. Still, Hansen and colleagues expected to see a heat source under Mount St. Helens, as seen at other volcanoes.

Instead, thermal modeling revealed a wedge of a rock called serpentinite that’s

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