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Dual volcano eruptions on Hawaii Island wind down

Madame Pele, Hawaiian goddess of volcanoes, is no longer in residence on either of the Big Island’s active volcanoes as experts document a significant coinciding decrease in eruption activity.

HONOLULU (CN) — For about two weeks, Hawaii’s Big Island hosted the rare phenomenon of two simultaneous volcano eruptions. But for now, both Mauna Loa and Kilauea have fallen suddenly silent.

The U.S. Geological Survey on Tuesday downgraded alert levels for both volcanoes to yellow ‘advisory’ from the orange ‘watch’ levels they had been assigned while they were actively erupting. Mauna Loa had been given a ‘warning’ red alert level during the first week of its eruption in November.

“On Dec. 10, all the lava that was in the channels was draining out, there was no new lava entering the channels, it was all contained in the cone sitting at the vent and that’s continued to be the case,” Ken Hon, the scientist in charge at Hawaii Volcano Observatory.

“There’s almost no SO2 coming out of the vent at this point, and we’re also seismically seeing very few earthquakes around the summit showing that the mountain is depressurized, and also volcanic tremors caused by gas being released has gone to almost nothing. All of those aspects show that the volcano is no longer erupting.”

Mauna Loa first erupted Nov. 27 after 38 years of silence, the longest period of repose documented for the volcano. It erupted for around two weeks, with lava production slowing down by weekend of the second week. The volcano observatory reported that Mauna Loa produced 200 to 250 million cubic meters of lava over 12 days, around 100 million more cubic meters than the usual for Mauna Loa.  

Kilauea, the island’s youngest and most active volcano, has been erupting nearly constantly for the last several decades. The most recent eruption began in late 2021 and had been primarily contained to the volcano’s summit. The observatory reported that Kilauea had been showing signs of winding down since even before Mauna Loa erupted, although they estimate that it only stopped erupting in the last week.

Geologists conducted a monitoring overflight of Kīlauea summit on the morning of December 10, 2022. They noted that the lava lake within Halemaʻumaʻu crater was mostly solidified, though incandescence was visible. (J. Bard/USGS)

Hon said it's a toss-up whether the simultaneous conclusions are related or merely a coincidence.

“Kilauea may have been diminishing already and the Mauna Loa eruption may have caused enough physical changes to stop it or it may have stopped on its own. We don’t really have a good answer right now; there’s a lot of data we’re going to be combing through in the next year to learn more about the relationship between the two volcanoes,” he said.

Although neither of these most recent eruptions were predicted to pose any threat to the general Big Island community, there were concerns that the flow of lava from Mauna Loa would block Daniel K. Inouye Highway, the main route between Hilo and Kona. The Mauna Loa lava flow stalled a little less than two miles south of the highway about a week ago.

The observatory expects some residual movement as the lava settles and inflates over the next several weeks, despite the lack of eruption activity. Big Island authorities caution against exploring Mauna Loa as hazardous conditions remain in place, warning that the lava could still be hot enough to boil water.

Based on historical trends, geologists do not expect Mauna Loa to resume eruption activity, although they will continue to monitor the situation with both volcanoes during the next several months as they go through a cooling-off period.

In contrast to the comparatively restful Mauna Loa, Kilauea had continuously erupting since 1983, ending with an explosive 2018 eruption. Activity then resumed from 2020 until May 2021, after which the recently ended eruption began in September 2021.

Kilauea’s 2018 eruption devastated the town of Puna in southeast Big Island in one of the world’s most disruptive volcano eruptions since Mount St. Helens. Thousands were evacuated and 13 square miles of residential property was overtaken by the flow. Unlike the Mauna Loa eruption, this eruption managed to reach the ocean, create 875 acres of new land on Big Island.

Mauna Loa, the world’s largest active volcano, also had experienced periods of recurring activity during the last several centuries. Hon said it's too early to predict if the volcano could return to the eruption frequency of the late 19th and early 20th centuries.

Hawaii County Civil Defense reported that Thursday would be the last day for the traffic mitigation route it had opened for volcano observers. Viewers will still be able to get their glimpse of the volcano from nearby parks and the Daniel K. Inouye Highway.

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