Volcano Watch: Pressure is on — within Kīlauea and for volcanologists to foretell what’s next

“Volcano Watch” is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates. This week’s article was issued Friday because of the national day of mourning Thursday in honor of the late former President Jimmy Carter.

The recent eruption of Kīlauea within Halemaʻumaʻu Crater, which started the early morning of Dec. 23, 2024, brought back an eruptive style not seen for many years.

The eruption has included 3 episodes of lava fountaining separated by pauses in activity.

The third pause is ongoing, and U.S. Geological Survey Hawaiian Volcano Observatory scientists are reviewing patterns of past eruptions and current monitoring data to forecast what could happen next.

Episodic eruptions have occurred before on Kīlauea: at the start of the 1983 Puʻuʻōʻō and the 1969 Maunaulu eruptions (44 and 12 episodes each) in the middle East Rift Zone, and during the 1959 Kīlauea Iki summit eruption (17 episodes).

While the recent Kīlauea summit eruption is currently paused, persistent night glow from the vent and continued strong degassing indicate molten magma is probably within 150 to 300 feet of the surface within the vent.

Sufficient pressure could push magma up to the surface to start another eruptive episode.

Fountaining is driven by rapid volume expansion of gas in fresh lava, but is commonly preceded by periods of eruption of sluggish degassed flows. Dense degassed material is pushed out of the vent like a cork from a champagne bottle, allowing gas-rich magma to rise rapidly and fountain.

Episodes are marked by the onset of lava fountains and rapid deflation of the source magma chamber. Pauses between fountain episodes are usually accompanied by reinflation of the summit.

A new episode begins when the system builds up enough pressure to force magma to the surface again.

The main feature of episodic eruptions is their repeatability, which allows patterns to be identified.

Inflation following episodes 1 and 2 of the recent eruption at the summit of Kīlauea resulted in 6 microradians of ground tilt recorded by a tiltmeter north of the caldera, near Uēkahuna bluff, indicating the pressure increase required at that time for the eruption to resume.

Following episode 3, Kīlauea has inflated and the 6 microradian level was reached about 4:30 p.m. Jan. 8 afternoon — 5 days after episode 3 paused at 8:40 p.m. Jan. 3.

That amount of inflation was the minimum amount of pressure required previously for this eruption to restart. However, the large deflation that accompanied the prolonged fountaining of episode 3 suggests the system might need more inflation to reach the pressure necessary for eruptive activity to resume.

The longer the vent sits without eruption, the more time magma within the vent has to cool and it could reach a point that the eruption can’t restart.

Assuming the vent remains open, indicated by continued glow and degassing, and inflation rate remains constant, a new episode could potentially begin sometime between Jan. 8 and Jan. 13, when ground tilt at Uēkahuna is expected to reach 12 microradians, about double prior post-fountain tilt increases.

Hawaiian Volcano Observatory scientists have been developing tools to estimate times of high probabilities of eruptions occurring on Kīlauea for the past several years.

Complex models using GPS monitoring data have been created to track when the summit approached pressurization levels similar to previous eruptions.

Models run in October 2024 indicated that Kīlauea was likely to reach pressurization levels where an eruption could happen between mid-December 2024 and mid-January 2025. This model also relies on the eruption being preceded by increasing numbers of earthquakes in the region where the eruption is most probable.

“Windows” of high probability for new eruptions or new fountaining episodes aren’t true forecasts.

A forecast requires knowing what will happen, where it will happen and, most importantly, an accurate estimate of when it will happen.

Forecasting when an eruption will happen is the most difficult part, but is very important so communities have more time to prepare if needed.

Whenever Hawaiian Volcano Observatory raises alert levels to Watch/Orange, we are issuing a more precise forecast for a pending eruption or intrusion within minutes to hours near the summit or hours to days further along Kīlauea’s rift zones.

Observatory scientists are constantly improving models of volcanic behavior — past, present and future — which allows us to forecast eruption time windows with greater accuracy and longer advance warning.

This is an essential part of Hawaiian Volcano Observatory’s mission to reduce the impacts of volcanic eruptions and communicate the results of our work to emergency managers and the public.

Volcano Activity Updates

Kīlauea is erupting. Its USGS Volcano Alert level is at Watch.

Eruptive activity at vents in the southwest portion of Kīlauea caldera paused the evening of Jan. 3.

Low inflationary tilt at the summit since then suggests the eruption could resume in the coming days to weeks, and lava was observed within the inactive vents during a monitoring overflight the morning of Jan. 10.

Recent eruptive activity has been confined to Halemaʻumaʻu Crater and the downdropped block within the caldera.

No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone.

Sulfur dioxide emission rates are elevated in the summit region during eruptive activity.

Earthquake rates in the Southwest Rift Zone and upper-to-middle East Rift Zone remained comparable to the previous week. Ground deformation rates outside of the summit region remained steady.

Mauna Loa is not erupting. Its USGS Volcano Alert Level is at Normal.

Three earthquakes were reported felt in the Hawaiian Islands during the past week:

• A magnitude-3 at 9:44 a.m. Jan. 7 located 6 miles south of Waikōloa at a depth of 14 miles.
• A magnitude-2.7 at 3:14 a.m. Jan. 4 located 6 miles south-southwest of Leilani Estates at a depth of 4 miles.
• A magnitude-3 at 4:18 p.m. Jan. 2 located 24 miles southeast of Nāʻālehu at a depth of 19 miles.

Hawaiian Volcano Observatory continues to closely monitor Kīlauea and Mauna Loa.

Visit the observatory’s website for past “Volcano Watch” articles, Kīlauea and Mauna Loa updates, volcano photos, maps, recent earthquake information and more. Email questions to askHVO@usgs.gov.