What to expect from this Kīlauea eruption? Scientist-in-Charge explains

Pele, the Goddess of volcanoes and fire, has returned home to Kīlauea.

The volcano that ranks among the world’s most active — and could even top that list — awakened shortly after 4:30 p.m. Thursday with a new eruption beginning in the central east portion of Halema‘uma‘u crater in Kīlaueaʻs summit region.

Several minor fountains were still active Friday, and lava flows have already inundated much of the 300-acre crater floor, which has a perimeter of about 2.75 miles.

Dubbed the January 2023 eruption, the lava is confined to Halema‘uma‘u crater and within Hawai‘i Volcanoes National Park. The Hawaiian Volcano Observatory does not see any indication of activity migrating elsewhere or threatening communities.

The new eruption follows a couple of weeks of elevated earthquake activity and gradual inflationary ground tilt at the summit.

“We could tell that the magma system wasn’t really taking a nap,” said Hawaiian Volcano Observatory Scientist-in-Charge Ken Hon. “There was still signs that things were moving around underneath, and the intensity of that is starting to pick up again.”

It is the volcano’s third eruption in a little more than two years. All of them have been confined to Halema‘uma‘u crater and the summit region. The most recent previous eruption began in September 2021 and stopped nearly a month ago.

That pause in activity allowed more magma to accumulate in the shallow chamber underneath Halema‘uma‘u, causing continuous inflation (ground surface swelling) as magma was stored up, pressurizing the system. That pressure and the release of volcanic gases led to multiple minor fountains, with several bursts of lava up to 164 feet high during the initial part of the eruption.

“The start of this eruption was a lot more spectacular because there was extra magma involved in the beginning of this one so it was much larger than it will be on the longterm,” Hon said.

While fountain heights were initially hundreds of feet high, they have since decreased in vigor and were consistently about 16 feet high Friday morning.

Before September 2021, the volcano erupted at the summit from December 2020 to May 2021.

Kīlauea’s alert level remains at watch, as high effusion rates are declining and no infrastructure is threatened. The aviation color code is at orange because there currently is no threat of significant volcanic ash emission outside the hazardous closed area in the park.

The higher-elevation island within Halema‘uma‘u crater that formed during the initial phase of the December 2020 eruption remains exposed, as well as a ring of older lava around the lava lake that was active prior to December of last year. The older lake has refilled from below with new lava.

Hawaiian Volcano Observatory geologists are working on quantifying how much lava has flowed since the new eruption began. According to geologist Katie Mulliken, there has been nearly 32 feet of new lava added to the base of Halema‘uma‘u so far.

Hon said a flyover is planned on Sunday to gauge how much of the crater floor has been covered by lava from the new eruption. He estimated just from looking at pictures that about 70% to 80% had been covered already by early Friday afternoon. The September 2021 eruption spilled out about 29 billion gallons of lava at an average rate of about 3 cubic meters per second, while the December 2020 eruption added about 11 billion gallons at an average of about 1 to 2 cubic meters per second.

The question right now is the composition of the lava flowing into the crater from the new eruption. Hon said none of the fountains have been big enough to eject lava outside Halema‘uma‘u, and scientists haven’t been able to get any samples yet. He added that the eruption is being fed by the same shallow magma chamber as the previous two eruptions, and there wasn’t much change in lava composition between the December 2020 and September 2021 eruptions.

The composition of lava gives scientists important clues about the magma under the summit and caldera, including how it is stored, how it is generated, and even how long it’s been in residence in the chamber.

Summit tilt (measure of the slope angle of the flank of a volcano) switched from inflation to deflation (ground above the reservoir subsiding) about 5 p.m. Thursday, and that trend continued Friday.

“Think of down underground there being a balloon, and that’s the magma chamber,” Hon said. “Basically, if you look at the top of a balloon when it’s not inflated very much, you put something on there like a bubble level and what you’ll see as you blow it up, that bubble level, if it’s not right in the very center at the top and slightly off to the side, will go from nearly horizontal to start tilting more and more as the balloon blows up and it becomes on the side of the balloon. When you let air out of it, it will go back down and it will become flatter and flatter.”

So as magma is stored and pressure builds in the chamber beneath the crater, that tilt goes up. When it starts to erupt, the tilt goes down.

“It’s doing exactly what it should,” Hon said.

Taking some of the pressure off is like letting air out of the balloon.

“You may say, ‘Well, it’s going right back into Halema‘uma‘u, but if you think about it, Halema‘uma‘u is kind of like a big cup right now, a bucket,” Hon said. “It’s just holding lava in it. It’s not exerting any pressure on the surrounding rocks, so it’s not tilting the rocks of the summit anywhere.”

Following the new eruption’s onset, summit earthquake activity greatly diminished and eruptive tremor, a signal associated with fluid movement and continued activity, resumed. Volcanic gas emissions in the eruption area also are elevated.

It seems Kīlauea is in a pattern of re-establishing its summit plumbing, Hon said. Shallow eruptions into Halema‘uma‘u have been the norm since the December 2020 eruption.

“Whether or not we can project how long this will continue, I can’t say,” Hon said, adding for right now, the pattern is continuing. “The shallow magma chamber just seems to be the place, and we’re directing the stuff up into Halema‘uma‘u and continuing this pattern of shallow eruptions into Halema‘uma‘u crater.”

This eruption has had no effect on nearby Mauna Loa volcano, which began erupting for the first time in 38 years on Nov. 27 and lasted a little more than two weeks before pausing.

How long this Kīlauea eruption will continue, however, is not as straightforward as the signs that signaled its beginning. Hon said a lot of times, eruptions just taper off and there’s no real signature marking their end. He added that future scientists might look back at this and Kīlauea’s previous two summit eruptions as just the the first three phases of 80 years of summit activity.

Unlike the 2018 Kīlauea lava flow — which inundated 14 miles of land, destroying 1,839 structures and damaging another 90 in Lower Puna — Hon said the shallow eruption pattern Kīlauea is now experiencing is a good one in which to be: “The lava is safely contained and people can go and take a look at it.”