HVO raises Mauna Loa alert level to “advisory”

UPDATED: It remains unclear whether the uptick of Mauna Loa activity is connected with the Kilauea eruption, said HVO scientist-in-chief Tina Neal.

Today’s increase in the Mauna Loa alert level — from “normal” to “advisory” — came just over one year after it was downgraded from advisory to normal in June 2018.

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While Neal said it is understandable to link the 2018 alert downgrade to the beginning of the Kilauea eruption, which began the previous month, she added that the link between the two volcanic systems is not yet clear.

Historically, Neal said there is evidence that when activity at one volcano increases, activity at the other decreases. However, there is “not a perfect correlation” between the two, she said.

Volcanic activity at Mauna Loa has been increasing for some time, Neal said, but there was no particular inciting incident that led to the increase in alert level.

“There’s no crystal bright line a volcano has to pass,” Neal said. “We’re mostly looking for a sustained rate of change.”

Neal confirmed that a magnitude 3.7 earthquake that occured Monday evening on Kilauea’s south flank was unrelated to the alert level increase.

The increased activity at Mauna Loa may cast light onto how the Kilauea eruption affected Mauna Loa, Neal said, although there is a hypothesis that the deformation caused by the eruption may have relieved some of the pressure on Mauna Loa. If that is true, Neal said, then it may take longer for Mauna Loa to erupt again.

“It will erupt someday,” Neal said. “So people should be prepared.”

To that end, Neal said HVO will return to putting out weekly updates on the volcano’s activity.

PREVIOUSLY: The Hawaiian Volcano Observatory has raised the alert level for Mauna Loa from “normal” to “advisory” following increased seismic activity.

The volcano has demonstrated higher rates of earthquakes and ground deformation than considered normal since October 2018, with HVO stations recording an average of at least 50 minor quakes per week and ground deformation similar to the volcano’s previous period of higher activity, which ended in 2018.

HVO also raised the aviation color code — which warns about ash-based hazards for aircraft — from green to yellow, indicating that the volcano displays signs of unrest, but without any detected emission of ash.

A statement from observatory emphasized that the higher alert level does not mean that an eruption is imminent and that the increased activity is not a cause for alarm. The previous period of higher activity lasted for four years at an “advisory”-level alert status without an eruption.

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However, the statement also advised communities on Mauna Loa’s flanks to remain prepared. While the volcano would be expected to reveal more signs of activity for days or weeks preceding an eruption, it is possible for that timeframe to last only days or hours.

HVO geologists have discussed raising the alert level for several months since the increased seismicity began last year.

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