Long-dormant volcano Mauna Kea has been quietly grumbling for decades
Hawaii’s long-dormant Mauna Kea volcano has been quietly and regularly rumbling for decades — but there’s no need for alarm. The tiny earthquakes aren’t signs of the volcano’s unrest, and are more likely linked to gases bubbling from a pool of slowly cooling magma deep underground, researchers report in the May 15 Science. Since at least 1999, the team reports, the ground deep beneath Mauna Kea has been shaking periodically, on timescales ranging from roughly every seven to 12 minutes. The source of the tiny quakes, each no more than about magnitude 1.5, is about 25 kilometers deep at the very base of Earth’s crust. It’s “one of the strangest seismic signals we’ve ever seen,” says Aaron Wech, a volcanologist at the U.S. Geological Survey’s Alaska Volcano Observatory in Anchorage. The long-lasting, highly periodic rhythm of Mauna Kea’s quakes is unusual. But small, deep, slow quakes are a familiar type of seismicity associated with volcanoes, says John Vidale, a seismologist at the University...