‘Unrest’ on Mauna Loa, no signs of imminent eruption

This USGS graphics shows the spike in earthquakes on Mauna Loa through Oct. 3.

On Sept. 8 Hawaiian Volcano Observatory staff replaced the gas measurement station at Sulphur Cone on the Southwest Rift Zone of Mauna Loa. Field staff (in orange) and the gas monitoring station are visible right of center in this aerial view, which also shows the 1950 fissure and Sulfur Cone. The Sulfur Cone is at an elevation of 11,240 feet above sea level. (T. Elias. / USGS)

HONOLULU — Mauna Loa, the largest active volcano on the planet, is in a “state of heightened unrest,” but is not erupting and there are no signs of an imminent eruption, the Hawaiian Volcano Observatory said in an update Friday.

Earlier this week, Hawaii Volcanoes National Park closed the Mauna Loa summit backcountry until further notice, calling it a “precautionary measure” amid “elevated seismic activity.”


The observatory said the heightened unrest began in mid-September, “as recorded by an increase in earthquakes below Mauna Loa summit.”

The volcano, which stands about 13,680 feet above sea level on the island of Hawaii, last erupted in 1984, the observatory said. Since 1843, it has erupted 33 times, with the time between eruptions ranging from months to decades, according to the observatory.

The park’s online portal says this is the volcano’s “longest quiet period since written records have been kept.”

“Mauna Loa will erupt again,” Ken Hon, scientist-in-charge at the Hawaiian Volcano Observatory, told the Honolulu Star-Advertiser. “As long as there is heightened unrest, it is more likely to erupt. But it could be weeks or months — or it could eventually die off.”

The latter happened the last time there was elevated seismic activity and summit expansion on Mauna Loa, in early 2021.

Hon said scientists don’t have much information to determine what normal behavior for the volcano is. There have been just two eruptions since 1950.

The observatory in recent years has urged residents living on Mauna Loa’s slopes to have a “go bag” with essentials and important documents in the event of any potential evacuation order. It is a readiness step local emergency managers also recommend.

Last year, state lawmakers directed the Hawaii Emergency Management Agency to develop an evacuation plan for Hawaii County in case of an eruption.

Hawaii County Civil Defense Administrator Talmadge Magno said his office has been assisting with the plan. A first draft is due in January.

If the need were to arise before that, Magno said: “We’re ready to respond.”

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