Volcano Watch: Kīlauea eruption signals significant, fascinating change

“Volcano Watch” is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates.

A new Kīlauea eruption began in a remote area of Hawaiʻi Volcanoes National Park on Sept. 15.

This is the first eruption on Kīlauea’s middle East Rift Zone since 2018 and it poses no immediate threat to life or infrastructure. The USGS Hawaiian Volcano Observatory is closely monitoring the eruption.

The Hawaiian Volcano Observatory has been in close contact with Hawai‘i Volcanoes National Park and Hawai‘i County Civil Defense throughout this eruption, which has featured a series of small fissure phases that have lasted hours to days.

Each phase has increased in volume, with the most recent being the largest so far.

In total, the fissure system has stretched more than 1.1 miles and lava has covered more than 192 acres.

The first phase of the eruption began between 9 and 10 p.m. Sunday.

Infrasound sensors in the Hawaiian Volcano Observatory’s monitoring network recorded strong signals indicative of gas or steam venting. At the same time, the Hawaiian Volcano Observatory’s seismometers recorded weak but sustained low frequency tremor.

Although an eruption could not be confirmed visually Sunday night by webcams or satellite thermal data because of heavy rainfall, the geophysical data indicated an eruption could be taking place.

That night, some residents in nearby communities also reported strong sulfur or burning smells.

The next morning, Sept. 16, Hawaiian Volcano Observatory scientists on a helicopter overflight confirmed that a small eruption occurred on Kīlauea’s middle East Rift Zone between Makaopuhi Crater and Nāpau Crater.

This first fissure eruption was small and covered less than 4 acres. Lava was no longer flowing on the surface as of Monday, but magma was still moving underground as detected by seismometers, tiltmeters and GPS.

Phase two of the eruption began Monday about 6 p.m.

The onset of this eruptive activity was detected in NOAA GOES satellite thermal imagery and Hawaiian Volcano Observatory webcam imagery.

Interestingly, no changes were detected in other monitoring datasets.

Fissures from this phase produced lava fountains and flows that gradually decreased through the night. But activity would soon resume.

The third eruptive phase began between 4 and 5 a.m. Sept. 17.

This onset was detected using a combination of infrasound signals, GOES satellite thermal anomaly and webcam imagery.

After sunrise, Hawaiian Volcano Observatory scientists on a helicopter overflight observed several lava fountains about 10 yards high generating lava flows on the floor of Nāpau Crater.

That eruptive phase was more vigorous and longer lived and continued before gradually decreasing levels through Wednesday afternoon.

A fourth eruptive phase began shortly after 3 p.m. Sept. 18, as new fissures opened west of Nāpau Crater.

A monitoring camera deployed by Hawaiian Volcano Observatory field crews with permission from Hawaiʻi Volcanoes National Park recorded “lava falls” cascading down the northwest walls of Nāpau Crater.

Vigorous activity continued into Wednesday evening and lava continued to cascade into Nāpau Crater as of Thursday morning.

Hawaiian Volcano Observatory webcam views are available on the observatory’s website including a new live view of Nāpau Crater.

How long will the eruption last? Examining history, numerous middle East Rift Zone eruptions took place during the 1960s and 1970s, most of which lasted less than a day to about 2 weeks.

An eruption near Nāpau Crater in 1997 lasted 2 days. The nearby 2011 Kamoamoa eruption lasted 5 days.

Of course, there have also been much longer-lived middle East Rift Zone eruptions as well. Maunaulu lasted 5 years and Puʻuʻōʻō lasted 35 years. Time will tell!

Looking at the bigger picture, this eruption signals a significant and fascinating change in activity at Kīlauea.

One year ago this week, a Kīlauea summit eruption in Halemaʻumaʻu was just ending. That eruption, which lasted from Sept. 10-16, 2023, was the fifth in a series of eruptions within Halemaʻumaʻu since December 2020.

On June 3, the first Kīlauea eruption outside the summit caldera since 2018 occurred several miles southwest of Halemaʻumaʻu.

And now, after a series of seismic swarms and magmatic intrusions beneath the upper East Rift Zone during the past few months, we are witnessing the first middle East Rift Zone eruption since 2018.

It seems that a new era of Kīlauea eruptions has begun.

Other Volcano Activity Updates

Mauna Loa is not erupting. Its volcano alert level is at Normal.

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

• A magnitude-3.1 quake 14 miles west of Volcano at a depth of 5 miles Sept 15 at 1:15 p.m.
• A magnitude-4.3 temblor 3 miles south-southwest of Volcano Village at 0 miles deep Sept. 14 at 4:25 p.m.

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.