The eruption of Kīlauea volcano, which began on September 15, 2024, presented unique challenges for scientists at the Hawaiian Volcano Observatory (HVO). Initial poor weather conditions hampered traditional monitoring methods, leading to an unexpected reliance on local residents to detect the first signs of eruptive degassing. The eruption, located west of Puʻuʻōʻō, experienced fluctuating sulfur dioxide (SO₂) emissions before abruptly ceasing on September 20, 2024. This event underscores the importance of community involvement in volcanic monitoring.

The onset of the eruption was obscured by a “dark and stormy night,” rendering HVO’s webcams ineffective due to poor visibility. Compounding the issue, the southerly wind direction prevented HVO’s gas monitoring stations from detecting any initial eruptive degassing. This combination of factors meant that traditional scientific instruments were initially unable to provide timely details about the eruption.

In a surprising turn of events, the first indication of the eruption came from the residents of Volcano, Hawai’i. Community members reported detecting “sulfurous odors and burning smells” via social media. This grassroots detection proved crucial in alerting HVO to the potential eruption, highlighting the value of community observations in volcanic monitoring. The residents’ reports served as an early warning system, demonstrating the importance of local knowledge in such situations.

Despite these community reports, some HVO staff members living in the area only smelled burning, without detecting sulfur. Their gas badges “didn’t register SO₂ (sulfur dioxide) above background.” The presence of residual hydrogen sulfide (H₂S) from the inactive Puʻuʻōʻō area, exacerbated by the rainy conditions, further complex the situation. As the report stated, “even amidst community reports of sulfur smells, we couldn’t be fully sure if there was an eruption.” This highlights the challenges in differentiating between background volcanic gases and new eruptive activity.

The weather cleared on September 16, allowing HVO to visually confirm the eruption. The initial SO₂ emission rate was measured at approximately 300 tonnes per day (t/d), suggesting a relatively small eruption.However, this was short-lived. By September 17, the eruption had intensified, with SO₂ emissions soaring to nearly 12,000 t/d. The winds shifted, allowing one of HVO’s East Rift Zone gas monitoring stations to “detect a whiff of the SO₂ as well.” By that afternoon, emissions decreased to about 3,500 t/d as the lava fountaining weakened. Emissions were similar, around 2,000 t/d, the next morning, September 18.

The eruption’s intensity continued to fluctuate. Later on September 18, activity escalated again, reflected in increasing SO₂ emissions. HVO scientists, using an ultraviolet (UV) camera, observed a more intense plume. gas scientists then “switched back to more reliable UV spectrometer measurements,” revealing a progressive increase in SO₂ emission rate over the course of the afternoon. In conjunction with the opening of new fissures and the progress of ‘lava falls’ cascading over Nāpau Crater rim, emissions increased from 5,000 t/d at about 3:30 p.m. to roughly 12,000 t/d at 5:00 p.m.

The peak of the eruption occurred on September 19, with SO₂ emissions reaching approximately 30,000 t/d. Though, the eruption was short-lived. By September 20, it was over, with SO₂ emissions plummeting to only 800 t/d. HVO gas scientists were able to measure gases from the last gasp of lava earlier that morning using an infrared spectrometer. The gases were low in carbon dioxide (CO₂), and thus derived from magma that previously lost CO₂ while in the shallow magma plumbing system before eruption, similar to other Kīlauea East Rift Zone eruptions and recent Kīlauea summit eruptions.

A final SO₂ emission rate measured on September 21 showed that just under 100 t/d of SO₂ were being emitted from the inactive fissures.By September 23, SO₂ emissions from the Nāpau fissures were undetectable on Chain of Craters Road.

The HVO utilized a range of instruments to track the variable gas emissions, including a UV spectrometer, a UV camera, permanent stations, and an infrared spectrometer. Despite this technological arsenal, the initial detection of the eruption was credited to the residents of Volcano. As the report concludes, “even though HVO was ultimately able to track the variable gas emissions throughout the Nāpau eruption with our UV spectrometer, a UV camera, permanent stations, and an infrared spectrometer, we certainly know we weren’t the first to sniff the gases from the Nāpau eruption – that honor still goes to the residents of Volcano!” This highlights the importance of integrating community observations with scientific monitoring for effective volcanic hazard assessment.

Volcano Activity Updates

Kīlauea has been erupting intermittently within the summit caldera as of December 23, 2024. Its USGS Volcano Alert level is WATCH.

The summit eruption at Kīlauea volcano that began in Halemaʻumaʻu crater on December 23 continued over the past week, with one eruptive episode. Episode 11 was active from the night of February 25 until the morning of February 26. Kīlauea summit has been inflating as episode 11 ended,suggesting that another eruptive episode is absolutely possible. Sulfur dioxide emission rates are elevated in the summit region during active eruption episodes. No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone.

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 M3.4 earthquake 14 km (8 mi) S of Volcano at 0 km (0 mi) depth on Feb.27 at 3:33 a.m.HST, a M3.3 earthquake 16 km (9 mi) W of Kailua-Kona at 14 km (8 mi) depth on Feb.23 at 9:31 p.m. HST, and a M2.7 earthquake 13 km (8 mi) NNE of Hawaiian Ocean View at 9 km (5 mi) depth on Feb. 20 at 7:36 a.m. HST.

HVO continues to closely monitor Kīlauea and Mauna Loa.