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Historic Maunaloa flows: What makes this one different?

Hawaii Volcano Explainer
John Swart
A gaseous cloud rises from the crater of Maunaloa, center, on the big island of Hawaii, April 4, 1984.

There's been a significant change in the eruption activity atop Maunaloa.

The supply to the lava flow headed toward the Daniel K. Inouye Highway has been cut off, meaning lava is no longer an imminent threat to the main road across the Big Island, the U.S. Geological Survey said Thursday. The development was a welcome reprieve for motorists who depend on the road.

“That’s good news for us,” Hawaiʻi County Mayor Mitch Roth said. Still, county officials said they will stay on the alert — because scientists say things could always change.

Lava from Maunaloa, which began erupting on Nov. 27 after being quiet for 38 years, was 1.76 miles from Saddle Road, also known as Route 200 or Daniel K. Inouye Highway, the USGS said.

While Fissure 3 continues to erupt, its production is reduced. Roth said the highway is still open in both directions and the eruption is not threatening any communities or structures.

The current eruption may be inspiring a new generation of volcanologists, but it was nearly four decades ago that young geology graduate Scott Rowland got his first chance to study lava flows on Hawaiʻi Island.

Rowland is now a professor at the University of Hawaiʻi at Mānoa and has studied volcanic flows across the world, under the sea and even on Mars.

But his first love will always be Hawaiʻi’s historical eruptions. The Conversation spoke with Rowland about how this latest Maunaloa eruption compares to other flows.

"The 1984 events were a little farther down rift than the current eruption vents are, but like the current eruption, it started with a summit phase up in Mokuʻāweoweo," Rowland said.

Maunaloa mauna loa lava 1984
Ken Love/AP
FILE - Molten rock flows from Maunaloa on March 28, 1984, near Hilo, Hawaiʻi. (AP Photo/Ken Love, File)

He said the 1984 eruption's volume per time coming out of the vent was higher than the current eruption is, but not by much. Instead of heading straight towards the saddle, where the current flow is stalled, the 1984 lava flows missed the saddle and curved down towards Hilo.

"And they were sort of worrisome for a little while, like almost all lava flows, they start off fast and they slow as time goes on," he said. "You see them coming down the hill towards Hilo. It's no wonder lots of folks were worried."

Rowland said more people live near Maunaloa now, which causes distress among residents who remember the 1950 eruption.

"Of course, a repeat of that type of activity is what people always worry about because think about 1950 compared to today, the number of people who live along that flank of Maunaloa has increased enormously."

To ease worries, he said that volcanoes are closely monitored, especially with the establishment of the Volcano Observatory in 1912.

"There wasn't any kind of instrumental monitoring or systematic measuring of things until 1912. Certainly, since the early 1960s, that's when the monitoring effort at Kīlauea and Maunaloa really took off," Rowland said.

This interview aired on The Conversation on Dec. 8, 2022. The Conversation airs weekdays at 11 a.m. on HPR-1.

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