Scientists Detect New Magma Movement Deep Within Three Sisters Volcanoes in Oregon

An aerial view from the south of South Sister, Middle Sister and North Sister in Oregon’s Cascade Range. | Courtesy of U.S. Geological Survey / John Scurlock

Scientists are seeing new signs that magma is moving deep within the Three Sisters volcanic complex in Oregon’s Cascade Range.

Equipment used by the U.S. Geological Survey to monitor volcanic activity has detected short bursts of tiny earthquakes across a 12-mile area where the ground has been lifting at a faster pace.

Jon Major, scientist in charge at the Cascades Volcano Observatory, said the activity is likely coming from pulses of magma moving about four miles underground.

“There’s no imminent threat,” he said. “Our interpretation is it’s probably related to ongoing small inputs of magma deep underground.”

If the volcano were close to erupting, Major said, the magma would be breaking more rock, generating bigger earthquakes, releasing gases and lifting the ground at a much faster pace.

“There would be a lot more signs that magma was making its way to the surface and poised for an eruption,” he said. “We’re not seeing any of that right now.”

The last time Three Sisters erupted was about 2,200 years ago. Major said it is likely to erupt again, but the latest activity is minimal compared to what scientists expect to see before an eruption.

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SOURCE: OPB, Cassandra Profita