Scientists provide more details about the recent infiltration of Kilauea magma
(Bevin) – Shortly after the recent magma intrusion at Kīlauea volcano was the subject of a Volcano monitoring article, and before the 5.7 magnitude earthquake required attention, the USGS Hawaiian Volcano Observatory provided a detailed informational statement about the event to the southwest of the summit.
From the February 9 statement issued by the USGS HVO:
Kīlauea volcano does not erupt. Magma intrusion occurred southwest of Kīlauea Peak between 27 January and 3 February 2024. Seismicity rates and ground deformation extending southwest of Kīlauea Peak toward the Koa’e fault system increased significantly and peaked on 31 January. More than 700 earthquakes have been detected today, and deformation patterns and ground fissures indicate the placement of a dike (a vertical sheet of magma). Seismicity and deformation rates gradually decreased from February 1 to February 2, and then decreased significantly on February 3. Seismicity and deformation rates stabilized as of February 9. The overall decrease in seismic activity and deformation indicates that this event is declining. However, there are still possibilities for renewed activity, and an eruption may occur without warning. No unusual activity has been observed along the Kīlauea East Rift Zone.
HVO raised the volcano alert level for Kīlauea from ADVISORY to WATCH, the aviation color code from yellow to orange, at 4:41 a.m. GMT on January 31, when there was escalating unrest with an increased likelihood of an eruption. HVO lowered its volcano alert level from WATCH to ADVISORY, and its aviation color code from ORANGE to YELLOW, at 8:10 a.m. on February 3, as volcanic activity decreased significantly but continued to be closely monitored for a possible renewed increase. Kīlauea remains in ADVISORY/YELLOW at the time of this information release.
The last eruption at Kīlauea Peak ended on September 16, 2023. After this eruption, seismicity and ground deformation remained at background levels until October 4-6, 2023, when more than 600 earthquakes and increased ground deformation rates were recorded southwest of Kīlauea Peak. Earthquakes and inflationary ground deformation have continued throughout the Kilauea Summit region intermittently, waxing and waning with long periods of increased activity alternating with long periods of little or no activity. Periods of increased activity included more than 200 earthquakes per day on October 22, October 26, November 21, December 7, and December 29-30, 2023. Relatively less active periods between these peaks still include 30-50 earthquakes per day.
On January 27, 2024, activity began to increase and more than 250 earthquakes occurred throughout the day. Then on January 31, seismic rates and ground deformation increased significantly. HVO raised the volcano alert level for Kīlauea from ADVISORY to WATCH, the aviation color code from yellow to orange, at 4:41 a.m. GMT on January 31, in response to escalating unrest with an increased likelihood of an eruption. More than 700 earthquakes were recorded on January 31. The depths of the earthquakes remained constant, 1-4 km (less than 1-2.5 miles) below the surface, and their magnitude ranged from a maximum of just over M3 to less than M1. HVO field crews on the caldera rim felt several earthquakes and reported rockfall at Halema’umau throughout the morning. GPS instruments located southwest of the caldera recorded movement of up to 20 cm (8 inches). Clinometers located near the summit of Oikahuna and Sand Hill (southwest of the caldera) showed more than 60 microradians of change. Satellite data acquired between 6pm GMT on January 31 and 6pm GMT on February 1 showed complex patterns of ground deformation; General contraction was observed at the summit, while areas southwest of the summit showed upwelling of about 50 cm (20 in) as well as spreading (along with subsidence). The magma did not reach the surface, although HVO field teams later observed ground fissures associated with ground deformation southwest of the caldera.
On February 1, activity began to gradually decline after a peak on January 31, when approximately 650 earthquakes were recorded that day. On February 2, approximately 550 earthquakes were recorded. Inclinometers similarly recorded lower ground displacement rates. On February 3, activity decreased significantly, with fewer than 200 earthquakes occurring over the course of the day, and the surface tilt stabilized. HVO lowered its volcano alert level from WATCH to ADVISORY, and its aviation color code from ORANGE to YELLOW, at 8:10 a.m. GMT on February 3, as volcanic activity decreased significantly but continued to be closely monitored for a possible renewed increase.
As of February 9, earthquakes and ground deformation have stabilized beneath the summit and the area extending 8–11 kilometers (5–7 miles) southwest of the caldera under the Kwai Fault System. Earthquake numbers are less than 10 events per hour, widely distributed from the summit to the southwest. Earthquake depths remain constant at 1-4 km (less than 1-2.5 miles) below the surface and their magnitude ranges from just over M2 to less than M1. Inclinometers near Sand Hill and Uēkahuna continue to show low rates of ground deformation.
Sulfur dioxide (SO2) emission rates remained low throughout this invasion. Field measurements indicated a sulfur dioxide emission rate of about 70 tons per day on January 17, 2024, which was similar to measurements in October, November, and early December 2023.
Seismicity and deformation rates in the upper part of the Kīlauea East Rift Zone were low to moderate during this event. No significant activity was observed in the middle to low-lying areas of the eastern rift zone.
Interpretation and context
Seismic patterns and ground deformation indicate that magma seeped under the southern end of the caldera starting on the morning of January 27. This activity waxed and waned until January 31 when a significant increase in seismicity and the tilt of the ground indicated that a dyke (a vertical sheet of magma) had been erected, triggering occasional earthquakes and rockslides within Halema’umau. By 5 pm GMT on January 31, the seismicity had moved southwest of the caldera toward the Kwai Fault System and inclinometers at the summit and south of the caldera began recording strong contraction. Clinometer modeling, GPS, and satellite radar interferometry (InSAR) data indicate that magma within the primary dike migrated to the southwest below the Koa’e fault system.
Intrusive activity began in the southern caldera area and extended southwestward toward the Koa’e fault system where it intersects the southwest fault zone near Muniki. Floor cracks, extending tens of meters (yards) in length and centimeters (inches) in width, were observed near Pu’ukoa’e and Twin Craters on the eastern edge of the Southwest Rift Zone, indicating a dike head breach beneath this zone. Fissures primarily cut off the bulk Keanakāko’i tephra that covered this area from the Kaʻū Desert region in 1790 AD. The relationship between the southern caldera, the Kwai Fault System and the Southwest Rift Zone is not well understood, but recent intrusive activity suggests that the region is dynamic and new paths can be created between these zones.
Several intrusions have been recorded in this area in the past, most recently in October and December 2023, in August 2021, and in May 2015. The August 2021 intrusion occurred here over the course of about a week and was followed by an eruption within Halemauma. Sh about a month later (the eruption that began on September 29, 2021). The May 2015 intrusion here lasted less than a week and occurred during ongoing eruptions within Halema’uma’u and at Pu’u’ō’ō. Intrusions also occurred here in the 1960s, 1970s, early 1980s, and in 2006. Only one of these events led directly to a brief eruption in that area; In December 1974, infiltration began following this path southward, but then erupted for less than 24 hours as a series of short fissure segments with a total length of 5 km (3 mi) as it turned southwest.
What do we do?
HVO raised the volcano alert level for Kīlauea from ADVISORY to WATCH, and the aviation color code from yellow to orange, at 4:41 a.m. GMT on January 31 due to significant escalating unrest with an increased potential for an eruption. HVO subsequently lowered the volcano’s alert level from WATCH to ADVISORY, and its aviation color code from ORANGE to YELLOW, at 8:10 a.m. on February 3, as the probability of an eruption decreased. HVO will re-evaluate alert levels and notifications as safeguards for activity.
HVO continues to monitor Kīlauea Volcano closely, watching for any signs of accelerating seismic rates, ground deformation, or signs of shallow seismic sites, which usually precede a new lava eruption or spreading dyke. The overall decline in seismic activity and deformation indicates that this event is waning. However, there are still possibilities for renewed activity, and an eruption may occur without warning.
HVO will continue to post daily updates on our website, along with photos, videos and maps as they become available (here).
HVO is in frequent contact with Hawaii Volcanoes National Park and Hawaii County Civil Defense. Courtesy of Hawaii Volcanoes National Park, HVO installed two semi-continuous GPS stations on February 2 in order to more comprehensively monitor ground deformation southwest of Kīlauea Peak.
What can we expect?
The overall decline in seismic activity and deformation indicates that this event is waning. However, unrest to the south and southwest of Kilauea’s summit continues, potential for renewed and increased unrest remains, and an eruption could occur without warning. It is unclear how long the unrest will continue. It is not possible to say with certainty whether the current unrest will lead to an eruption. Although it is not possible to predict a specific outcome, here are three possible scenarios that could occur in the coming days or weeks:
1. Magma continues to accumulate in the area southwest of Kilauea Peak, but eventually stops without an eruption.
2. Magma continues to accumulate in the Kilauea summit area, with volcanic eruptions within the caldera, similar to recent eruptions at Halema’umau. In this scenario, we would expect to see signs of recompression of the magma reservoir beneath Halema’uma’u before rates of ground deformation and seismicity under the caldera accelerate an hour or two before the lava reaches the surface.
3. Magma continues to accumulate in the area southwest of Kīlauea Peak, with eventual eruption outside the caldera, to the south or southwest. In this scenario, we would expect to see earthquake sites migrating away from the caldera as observed in December 1974, followed by accelerated rates of ground deformation and seismicity an hour or two before the lava reaches the surface.