Hawaii & Alaska
Map released by the USGS to show progress of Mauna Loa's eruption in the first 24 hours. The red arrow shows where lava is currently flowing. USGS/FACEBOOK

HI - Mauna Loa Eruption Map Shows Where Lava Flow Is Heading on Hawaii

The largest active volcano in the world, Mauna Loa, has now been erupting for 24 hours. Initially contained in the volcano's summit crater, the eruption has now moved into the Northeast Rift Zone, where three eruptive fissures have burst open, spilling lava down the volcano's flanks.

The eruption was announced by the USGS at 11:30 p.m. HST on November 27. No populated areas are currently under threat, but the USGS is keeping a close eye on the situation.

In a Facebook post at 1 a.m. ET, the organization shared an updated map showing how the eruption had progressed along the rift zone, with one active lava flow advancing to the north of the island.

University of Oxford volcanologist David Pyle told Newsweek that lava flows are the main threat from this sort of eruption. "The main hazards from Mauna Loa eruptions are related to lava flows," he said. "At the moment the eruptive activity is confined to the summit region, which is a part of a rift zone that runs across the volcano.

"The rift has quite steep sides, and erupted lava can be confined to this rift zone, or buffer zone, for some time, depending on how the eruption proceeds."

Rift zones are areas of weakness in a volcano that are prone to volcanic activity. As the pressure builds up underground, magma ascends from deep reservoirs and forces its way up through the rock. Rift zones easily give way to cracks in their surface as a result of this pressure, producing fissures that spit out explosive fountains of lava.

That is what happened at Mauna Loa, where three such cracks opened up in the North East Rift Zone. Now only one remains active, with a vigorous flow of lava heading out of the rift zone.

"The main risk is the risk of inundation, from flowing lava," Pyle said. "This will depend on where the vent is; and on the amount of lava that then erupts, and how quickly—and these will all be features that the USGS scientists will be tracking during the eruption."

Plane above erupting volcano with lava
Photo from the morning overflight showing fissure and lava flows on Mauna Loa's Northeast Rift Zone at approximately 9:30 a.m. HST on November 28, 2022.K. LYNN/USGS

Mauna Loa takes up over half of the land area on Hawaii's Big Island and rises to an elevation of 13,000 feet above sea level. The last time Mauna Loa erupted was in 1984, when the lava front came within four miles of Hilo, one of the biggest cities on the island.

"The USGS has used data from historical eruptions to map out the locations of vents that formed during eruptions; and to map out the pathways followed by earlier lava flows," Pyle said. "These maps define the 'inundation zones' around Mauna Loa, that have been used by civil defense teams to develop emergency plans, in the event of a new eruption."

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