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Officials hope Mauna Loa eruption mirrors 1984 event

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An eruption began late Sunday night in the summit caldera of Mauna Loa, the first since 1984 for the world's largest volcano.

Although it’s been nearly four decades since Mauna Loa came to life, the current eruption so far has a familiar 1984 feel to it.

As in 1984, the initial late-night curtain of fire occupied the summit caldera before migrating toward the upper southwest rift zone. But within a few hours the activity shifted to the remote northeast rift zone, where the area’s vents became the focus of eruptive activity.

Officials with the Hawaiian Volcano Observatory said they hope the 1984 parallels continue, since the lava flows four decades ago grew more viscous and slowed as they hit the flatter terrain of the Big Island’s Saddle region.

The eruption stopped in 22 days, more than 4 miles from Hilo.

But you never know what will happen with the world’s largest active volcano.

The geological record indicates that Mauna Loa has erupted 33 times since 1843, with intervals between eruptions ranging from months to decades. Before 1950, the record shows, it erupted every five to six years. This eruption would be only the third since 1950.

Kilauea, meanwhile, has been very active, spewing lava more years than not since 1950 — and it continues to this day.

Scientists say that when Mauna Loa does erupt, it varies from Kilauea in that it tends to generate voluminous amounts of fast-moving lava capable of flowing into communities on both sides of the island.

Hilo has been threatened by seven Mauna Loa lava flows over the past century and a half — although only two actually made it into the outskirts of town, according to HVO.

On the other side of the island, flows reached the south and west coasts of the island eight times, including in 1950 when it took only three hours for the lava to reach the Kona Coast.

Ken Hon, scientist-in- charge at the Hawaiian Volcano Observatory, said there is no history of Mauna Loa erupting from two different rift zones at the same time, so it appears the residents on the west side of the island are safe for now.

As for Hilo, that’s another question.

“In the long term, eventually this kind of lava flow may be very similar to what happened in 1984,” Hon told reporters Monday. “It could potentially threaten populated areas around Hilo, but we’re looking at somewhere around a week before we expect lava to get anywhere near in that direction.”

“We’re hoping that it will parallel the 1984 eruption,” he said — and that includes lava growing in thickness over time and slowing down in the uninhabited backcountry well clear of Hawaii island’s most populous city.

He said he wouldn’t be surprised if the eruption was over in a week or two, based on the historical average.

“There’s no guaranteeing that that is what we’re going to get,” he said. “We’ve had eruptions that are much shorter and much longer. We’ve had eruptions as long as a year come from the rift zones and as short as just a few days. We won’t really know until the eruption’s over how long it’s going to be.”

Hon said it’s unlikely there will be a three-month-long event like the 2018 Kilauea eruption that destroyed more than 700 homes, changed the Puna landscape and caused damage estimated at more than $800 million.

University of Hawaii earth sciences professor Ken Rubin called the initial stages of the Mauna Loa eruption “reassuring.”

“But time will tell how all this progresses,” he said in a tweet.

Rubin said the eruption comes after by far the long­est quiet period for the mountain in nearly two centuries. The previous record repose was 25 years, between 1950 and 1975.

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