It’s been 33 years since Mauna Loa last erupted, but an alert level remains in place at the world’s largest active volcano. Scientists at Hawaiian Volcano Observatory raised the alert level two years ago. HPR Contributing Reporter Sherry Bracken says that although scientists say no eruption is imminent, they want Hawai'i Island residents to be aware of the likelihood of a future eruption.

Hawaiian Volcano Observatory Chief Scientist Tina Neal explains why her team raised the alert level in 2015.

“Two years ago, after observing many months of slightly elevated earthquake activity and steady inflation of the summit area of the volcano, we decided the volcano had departed from what we call its background quiet state. It was entering a period of restlessness, where these two volcano monitoring parameters, deformation and seismicity, were above the baseline. We were very clear, there was no imminent eruption, it just meant the volcano was restless. “

Neal said HVO and its partners—Hawai'i Volcanoes National Park and Hawai'i County Civil Defense—are working together to prepare for a future eruption. Neal says they’re also adding additional monitors to Mauna Loa.

“We already have several dozen seismometers and GPS instruments scattered around the volcano. It is a fairly well monitored volcano. But we always have gaps. We are putting in some additional monitoring equipment, another gas sensor high on the southwest rift zone of Mauna Loa, an additional seismometer high on the east flank.”

Scientists will be able to give many weeks’ notice of a pending eruption of Mauna Loa—which makes up more than half of Hawai‘i’s land mass. But where it will erupt, Neal says that’s uncertain.

“The historical eruptions almost always start in the summit region, above 12,000 feet, about half stay there, another quarter go down the northeast rift zone, another quarter down the southeast rift zone.”

In 1984, lava came within four miles of Hilo. But previous eruptions have gone to Ka‘ū and South Kona. In 1950, lava reached the ocean within three hours. Neal says there will be public outreach meetings early in 2018.