As we speak, an eruption has started within Kilaueau. HVO reported:
“Shortly after approximately 9:30 p.m. HST (7:30 am GMT, 2 hours ago) , the USGS Hawaiian Volcano Observatory (HVO) detected glow within Halemaʻumaʻu crater at the summit of Kīlauea Volcano. An eruption has commenced within Kīlauea’s summit caldera. The situation is rapidly evolving and HVO will issue another statement when more information is available.”
Shortly after, Honolulu reported
“web cams and radar data indicate a strong eruption has occurred at Halemaumau Crater. Low level trade winds will push any embedded ash toward the southwest, and any fallout will likely occur over the Kau District and Highway 11 southwest of the town of Volcano. This includes the communities of Pahala, Wood Valley, Naalehu and Ocean View.”
It followed an intrusion in Dec 2, and a second one over the past few days. GPS has shown strong inflation since September. It still came as a surprise to everyone. I for one had not expected the eruption to be inside the crater.
The lake, I am sad to report, is gone.
We will update this post as information becomes available. The chances are that this will be short-lived, but who knows.
This is the first image that shows the eruption. It was taken with the thermal camera on the west side. The eruption began just below the camera. This is not the same location as the later eruption, which was on the left side of the pit as seen from this angle. The eruption started no earlier than 1-2 minutes before this was taken
The map below shows the recent layout of the caldera. The 2018 eruption ended the lava lake here and caused a deep collapse. The deepest point was later taken up by the lake (which ended its existence today). Today’s eruption happened near the lake, perhaps on the steep slope, and the lava flowed into the pit. There were no phreatic explosions reported (although there were some minor bangs), and perhaps the lake had already drained before the lava got there.
The eruption is coming from a fissure along the wall of the pit, as shown in the HVO map below. Interestingly, this is near the centre of the original Halemauau crater – which of course may be purely a coincidence. Magma always goes for the easiest pathway, and a steep slope can provide this. It was along a pre-existing fault, and the slope provided an access point. The eruption started at the large dot on the left (the camera is just above this), at 21:30 HST. The next spot started two minutes later, and died again at 21:48. At this time the eruption almost stopped. It resumed strongly at 22:12 when the rift opened up. At 22:24 the final spot erupted, and this quickly became a focal point. The lake filled with lava at 23:20, 2 hours after the lava began to flow. Around 1 am the first eruption point began to decline.
The eruption rate is hard to calculate, but based on the fact that it has filled the lake (perhaps aided by some slides and some inflation below), I estimate it around 50 m3/s.
We provide the text of the HVO announcement this morning verbatim. It is highly informative.
For the past several weeks, the USGS Hawaiian Volcano Observatory (HVO) has recorded ground deformation and earthquake rates at Kīlauea Volcano’s summit and upper East Rift Zone that have exceeded background levels observed since the conclusion of the 2018 lower East Rift Zone eruption and summit collapse.
Beginning in September 2020, increased rates of uplift were observed by GPS stations in Kīlauea’s upper East Rift Zone. In the past month, increased uplift has also been measured at GPS stations in Kīlauea’s summit region. While uplift related to post-collapse inflation of the summit reservoir has been occurring since March of 2019, rates have been steadily increasing in recent months and are currently higher than they have been since the end of the 2018 eruption.
In late November 2020, increased earthquake rates began when seismic stations recorded an average of at least 480 shallow, small-magnitude earthquakes (97% of which were less than or equal to magnitude-2) per week occurring at depths of less than 4 km (2.5 miles) beneath Kīlauea’s summit and upper East Rift Zone. This compares to a rate of fewer than 180 per week following the end of Kīlauea’s 2018 eruption and through early November 2020.
On December 2, 2020, GPS stations and tiltmeters recorded a ground deformation event at Kīlauea’s summit. Accompanied by earthquake swarms, the patterns of ground deformation observed were consistent with a small dike intrusion of magma under the southern part of Kīlauea caldera. The injection resulted in about 8 cm (3 inches) of uplift of the caldera floor, and modeling suggests that it represented 0.4–0.7 million cubic meters (yards) of magma accumulated approximately 1.5 km (1 mile) beneath the surface. Though the intrusion did not reach the surface and erupt, it represented a notable excursion from trends observed in Kīlauea summit monitoring data streams following the end of the 2018 eruption.
On December 17, 2020, seismometers detected a notable increase in occurrence and duration of long-period seismic signals beneath Kīlauea’s summit, which are attributed to magmatic activity. Whereas this type of seismicity was observed on average once every few weeks following the 2018 eruption, rates have increased to over a dozen in the past several days.
Other monitoring data streams including volcanic gas and webcam imagery were stable until this eruption.
An earthquake swarm began on the evening of December 20, accompanied by ground deformation detected by tiltmeters. An orange glow was subsequently observed on IR monitoring cameras and visually beginning approximately 21:36 HST.
Since the early 1800s, when written records of Hawaiian volcanoes began, Kīlauea has had infrequent periods during which no lava erupted.
The longest known eruptive pause was in 1935-1952, ending with eruption in the caldera. Neither that 17-year pause, nor any other shorter pause, followed partial collapse of the caldera such as the collapse that occurred in the summer of 2018.
Following partial caldera collapses, the first eruption outside the caldera took place on the East Rift Zone 17 years after the 1823 collapse, on the Southwest Rift Zone 28 years after the 1840 collapse, and on the Southwest Rift Zone 52 years after the 1868 collapse.
After partial caldera collapses in 1840 and 1868, lava returned to the caldera within days to a few weeks. The length of the current pause exceeds those earlier post-collapse pauses.
Kīlauea Volcano has maintained a low level of non-eruptive unrest since the end of the 2018 lower East Rift Zone eruption and summit collapse, which deepened Halemaʻumaʻu crater by over 500 meters (1640 feet). Following the 2018 eruption, ground deformation rates have indicated steady inflation of Kīlauea’s summit and at the end of 2018, the HVO monitoring network detected Deflation-Inflation events (DI-events) indicative that the shallow Halemaʻumaʻu magma reservoir, located approximately 1.6 km (1 mile) under Kīlauea caldera, still contained significant amounts of magma.
In late July 2019, ponded water appeared at the base of the deepest collapsed area of Kīlauea’s summit, within the Halemaʻumaʻu crater. Since then, the body of water has grown into a lake, which continues to rise as it seeks equilibrium with the surrounding groundwater.
All communities on or near Kīlauea’s summit and rift zones should be prepared.
HVO continues to monitor the volcano closely and will report any significant changes. HVO is in close touch with National Park Service and Hawaii County Civil Defense and other agencies responsible for public safety.
Stay informed about Kīlauea by following volcano updates and tracking current monitoring data on the HVO web page (https://www.usgs.gov/volcanoes/kilauea/volcano-updates) or by signing up to receive updates by email at this site: https://volcanoes.usgs.gov/vns2/.
The County of Hawai‘i Civil Defense Agency is in constant communications with HVO. If anything develops that may affect your safety, you will be informed. Please sign up for Civil Defense notifications by visiting the County of Hawai‘i Civil Defense Agency webpage at http://www.hawaiicounty.gov/civil-defense/.