HVO: Unclear if unrest at Big Island’s Kīlauea volcano will continue as activity diminishes again

Unrest continues to the south and southwest of Kīlauea volcano’s summit on the Big Island, although activity has diminished again.

That’s the latest from the Hawaiian Volcano Observatory this morning in association with an intrusive event that began in the summit area earlier this month.

The observatory’s daily Kīlauea update from just before 9 a.m. said the unrest might continue to wax and wane with changes to the input of magma into the area.

“It is unclear if unrest in Kīlauea summit region will continue and it is not possible to say with certainty if activity will lead to an eruption; activity may remain below the ground surface,” said the update. “However, an eruption remains possible, most likely in Kīlauea’s summit region inside of Hawai‘i Volcanoes National Park and away from infrastructure.”

The summit remains at a high level of inflation. While there is no sign of an imminent eruption, increased inflation and earthquake activity are expected to precede eruptive activity. During periods of heightened unrest prior to recent eruptions at Kīlauea summit, signs of imminent eruption did not appear until 1 to 2 hours before lava reached the surface.

No unusual activity has been noted along Kīlauea’s East or Southwest rift zones.

Seismic swarm activity has varied since it began in the summit area earlier this month, with the greatest number of earthquakes occurring between Oct. 3-6, 16-18 and 21-23.

During the past 24 hours, swarm activity has diminished somewhat, with approximately 95 earthquakes recorded in Kīlauea’s summit region, a decrease from 174 during the previous day. Most of the earthquakes related with this unrest have been smaller than magnitude 2 and at depths of aboout 0.6 to 2 miles below the surface.

In addition to discrete earthquakes, seismic signals indicating magma movement, such as low-frequency tremor, have also been observed at Kīlauea summit stations, most recently yesterday afternoon.

The Uēkahuna summit tiltmeter located north of the caldera began to show deflation the morning of Oct. 23, following a few days of a generally flat trend. The Sand Hill tiltmeter, located just southwest of the caldera, showed ongoing inflation during the past 24 hours, though to a lesser degree than during previous days.

Overall, inflation at the summit remains high and has surpassed the level seen just before the most recent eruption that began Sept. 10 and last less than a week. However, the current rate of inflation in the region has diminished significantly since Oct. 4-6.

Similar patterns of earthquake activity and ground deformation occurred to the south of the caldera prior to the September and June 2023 eruptions in Kīlauea’s summit caldera, in Halemaʻumaʻu crater and on the downdropped block.

It is unclear how long the current unrest will continue and it is not possible to say with certainty if it will lead to an eruption. Although it is not possible to forecast an exact outcome, here are three possible scenarios that could play out in the coming days to weeks:

• Magma continues to accumulate in the region south-southwest of Kīlauea’s summit, but eventually stops with no eruption.
• Magma continues to accumulate in the region south-southwest of the summit, with an eventual eruption inside the caldera, similar to recent eruptions at Halema‘uma‘u. In this scenario, accelerating rates of ground deformation and earthquakes beneath the caldera would be expected 1 to 2 hours before lava reaches the surface.
• Magma continues to accumulate in the region where unrest is happening, with an eventual eruption outside the caldera to the south or southwest. In this scenario, earthquake locations would be expected to migrate away from the caldera as they did prior to the December 1974 eruption, followed by accelerating rates of ground deformation and earthquakes 1 to 2 hours before lava reaches the surface.

Volcanic gas emissions currently pose the greatest hazard to areas downwind of Kīlauea’s summit. Sulfur dioxide emission rates remain low, however, and were measured Oct. 19 at a rate of about 100 tonnes per day.

For discussion about Kīlauea hazards, click here.

Hawaiʻi Volcanoes National Park visitor information can be found here.

With permission from the national park, the Hawaiian Volcano Observatory has installed two new webcams to monitor the region where the unrest is happening at Kīlauea’s summit, the S2cam and MITDcam.

All Kīlauea summit webcam views are available here.

The Hawaiian Volcano Observatory continues to closely monitor Kīlauea, watching for any signs of accelerated rates of earthquakes or ground deformation or signs of shallowing earthquake locations, which usually precede a new outbreak of lava or propagating dike.

The observatory is also closely monitoring gas emissions and webcam imagery.