Mauna Loa flow front is cut off, immediate threat to highway infrastructure diminishes

Flow front cut off
Immediate threat to DKI Highway significantly reduced

Update: 9:36 a.m., Thursday, Dec. 6, 2022

Field crews report that while the eruption continues out of Mauna Loa’s active fissure 3, the supply of lava from the fissure to the flow front has been cut off, and is no longer advancing towards the Daniel K. Inouye Highway.

“It is no longer feeding the major channel going towards the highway,” said David Phillips, Deputy Scientist-in-Charge of the USGS Hawaiian Volcano Observatory during a morning press conference today.

As of this morning, the flow front was 1.76 miles from the highway, and HVO scientists say lava is coming out at what appears to be a reduced production rate.

The USGS reports that in addition to the change at the flow front, the height of the fountaining of lava at fissure 3–estimated at several hundred feet–was significantly higher overnight.

Phillips gave possible reasoning behind the change saying the higher fountaining could be due to constriction of the vent. Another possible reason is a transitioning of the flow from ‘A’ā (a Hawaiian term for lava flows that have a rough rubbly surface composed of broken lava blocks called clinkers, according to the HVO) to Pāhoehoe (Basaltic lava that has a smooth, hummocky, or ropy surface).

At this time, the flows are covering up previously erupted lava, and there’s no major organized new lava flow at this time. Phillips said the lower output of lava is resulting in a disorganized system of flows immediately around the vent.  

As of this morning, there were no actively fed flows below the Observatory road, according to Frank Trusdell, a research geologist at the US Geological Survey’s Hawaiian Volcano Observatory.  

“People will see residual activity along the fronts as the channels drain… Because the distal parts of the flow have been cut off from magma, one of the questions that people are wondering is if we have additional flow in the channel, can that then reactivate the flow front and push the lava closer to the highway.  Because we are dealing with ‘A’ā flows, it’s very unlikely that a supply of molten material from the top push the flow front at the distal margins ahead.  Essentially we have to renew the entire flow field with supply directly from fissure 3 to go all the way back down the entire distance to become a threat.”

Right now, we don’t expect that the new lava coming out on the surface to be able to replenish the supply to the flows that are closest to the Daniel K. Inouye Highway… The flows would have to renew themselves from the vent, flow over the existing lava flow field, and get down into the same area to be a potential threat again,” said Trusdell.  

Scientists said that since the eruption is still active, they cannot dismiss future threats.  In an effort to remain vigilant, field crews and observatory staff continue to monitor lava productivity.

*This is a new development and this post will be updated as more information is gathered.

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The eruption at Mauna Loa is now in its 11th full day with continued activity at fissure 3, which is generating a lava flow that is traveling north toward the Daniel K. Inouye Highway (Saddle Road).

As of 8 a.m. on Thursday, the flow front was advancing at a rate of 20 feet per hour, and was last measured about 1.75 miles from Saddle Road, according to the USGS Hawaiian Volcano Observatory.

Eruptive activity is confined to the Northeast Rift Zone where the flows “advance more slowly, spread out, and inflate on the flat ground between Mauna Loa and Mauna Kea,” according to the HVO.

This latest eruption began the evening of Nov. 27, 2022.

HVO field crews and USGS analysts have mapped some of the most active flows, displayed in red in the map below. Lava flow expansion over the past 24 hours is shown in dark red and amounts to 0.38 square miles (179 acres), according to the USGS.

Since 1843, Mauna Loa has erupted 33 times, averaging one eruption every 5 years, according to the HVO. Scientists note that prior to the current eruption, there was a 38 year quiet period, the longest on record.