Mauna Loa eruption comes after longest quiet period in recorded history

Until Sunday, Mauna Loa hadn’t erupted for 38 years.
Published: Nov. 28, 2022 at 11:49 AM HST|Updated: Nov. 29, 2022 at 4:37 PM HST
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HONOLULU (HawaiiNewsNow) - Until Sunday, Mauna Loa hadn’t erupted for 38 years.

That was the longest known quiet spell for the world’s largest active volcano.

The U.S. Geological Survey says that since 1843, Mauna Loa has erupted 34 times ― and has average of one eruption every five years. However, prior to 1950, the volcano averaged one eruption every 3 1/2 years.

Before Sunday, the most recent eruptions occurred in 1974 and then 1984.

In the eruption that started March 25, 1984, lava flows advanced 15 miles in three days, sending rivers of lava within 5 miles of the outskirts of Hilo. Fortunately, communities were spared and the eruption ended on April 15.

The Hawaiian Volcano Observatory said all recorded eruptions of Mauna Loa have started within the caldera at the summit of the volcano. About half of those eruptions remained confined to the summit area.

But the other half migrated downslope, usually going south and west from rift zones that run from the caldera to northeast and the southwest.

Scientists still don’t know what will happen in the newest eruption although it seems to be confined to the northeast rift zone, which poses less threat of rapid flows.

Mauna Loa has a history of massive eruptions that threaten communities on its slopes.

The most recent example was in January 1984, when an eruption in the same rift zone as this week eventually sent a lava flow towards Hilo. Adding to the drama was the rare simultaneous eruption with Kilauea.

Elisa Yadao was a young reporter for KGMB, sent to cover an eruption that would eventually threaten her hometown.

“Initially, it was wonderful. You know, it was exciting. The two volcanoes were erupting. And it was, I’ve never seen anything like it in my life,” Yadao said.

But within days, it became clear the flows were slowly and steadily headed towards Hilo.


Civil Defense Director Harry Kim faced a terrified community.

“I knew and still today the same,” Kim recalled. “When Mauna Loa erupts it will create—it’s like the word tsunami because we have a history of deaths so when Mauna Loa erupts it will create a different fear from Kilauea.”

Kim said he knew the public needed regular and accurate updates and committed to making two announcements a day about the progress of the flow. He said he depended on radio and meetings in the affected communities. Yadao was at one of those meetings, at a gymnasium in Kaumana outside Hilo.

“And in the gym, you could see the panic on people’s faces, because there’s nothing you can do if the lava flow is coming,” she said.

That flow stopped four and a half miles from Hilo.

And that was far from the first time the town was spared.

In 1935, Gen. George Patton sent bombers, which had little affect. The bombs either blew up in the lava or bounced off the rock nearby. The flow stopped on its own.

In 1881, as a slow-moving flow again approached the town, Princess Ruth Keelikolani left Oahu answering the call for help. University of Hawaii Geology Professor Scott Rowland said the flow was moving so slowly that the princess had plenty of time “to sail across and hike up to the flow front and beseech Pele to stop erupting.”

Roland said Mauna Loa eruptions are rarer now, which adds to the fear and uncertainty.

“If we were talking 100 years ago we would say, “Oh yeah, Mauna Loa’s erupting again. It’s no big deal it last erupted seven to eight years ago.’ It would not be such a surprise,” he said.