Geophysicists are using a network of electrical sensors that act like giant metal detectors to study molten rocks beneath the active volcanoes. The sensors have helped them understand how magma, which is formed 50 miles below our feet, reaches the fiery rims of active volcanoes. According to a study published in the journal Nature, scientists have painted a detailed picture of the plumbing below the active volcano Mount Rainer in Washington.

Active Volcanoes

Mount Rainer is among the most dangerous volcanoes

Researchers found that most of the magma is formed deep in the mantle. Water trapped in the oceanic crust escapes into the mantle, changing the melting temperature of surrounding rocks. The magma then rises up in a huge vertical column, pooling in a reservoir just below the volcano’s peak. Mount Rainer and Mount St. Helens are among the most dangerous volcanoes in North America. In May 1980, lava erupting from the Mount St. Helens killed about 50 people.

It has helped scientists answer the question whether magma goes up through a network of cracks, or is dragged up in little bits or moves upward in diapirs. R. Shane McGary of the Woods Hole Oceanographic Institute and lead author of the study said diapirs are something that you’d see in a lava lamp. It’s “a blob that gets heated up and rises,” said McGary.

Why volcanoes are where they are

Findings of the study suggest that Mount Rainer lies on top of a giant “chimney” of melt. However, preliminary evidence indicates that the nearby volcanoes in Oregon don’t have this configuration. It reveals that even neighboring volcanoes could have different eruption dynamics. Though no eruptions are imminent, McGary believes that Mount Rainer is a much bigger short-term threat than Mount Jefferson in Oregon.

Mount Rainer has the tallest peak among volcanoes in the Cascade Range. It is located 54 miles southeast of Seattle, Washington. The University of Alberta geophysicist Martyn Unsworth said that this study can’t tell us when Mount Rainer is going to erupt next time. But it reveals why volcanoes are where they are.