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Kilauea's Eruption Reduces in Vigor Overnight, USGS-HVO Lowers Alert Level

1:49 AM · Sep 12, 2023

The eruption within Kīlauea's summit caldera continues with lava fountains stretching approximately 0.8 miles across the Halema‘uma‘u crater floor stretching east onto the down-dropped block. Despite the ongoing activity, the Hawaii Volcano Observatory (HVO) has lowered the volcano alert level and aviation color code due to stabilized conditions. Volcano Alert Level: Lowered from WARNING to WATCH Aviation Color Code: Reduced from RED to ORANGE Lava Fountain Height: Up to 50 feet Seismic Activity: Dominated by eruptive tremor SO2 Emissions: High at 100,000t/d yesterday evening but decreasing Rift Zones: No unusual activity observed. ————————— USGS-HVO Morning Update (8:55am HST) Activity Summary: The Kīlauea summit eruption that began yesterday at 3:15 p.m., September 10th, continues this morning. Eruptive activity is confined to the downdropped block and Halemaʻumaʻu crater within Kīlauea's summit caldera. No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone. Halemaʻumaʻu Lava Lake Observations: Multiple minor fountains remain active in the eastern portion of Halema‘uma‘u crater floor and on the downdropped block within Kīlauea's summit caldera. The line of vents stretches approximately 0.8 miles (1.4 km), from the eastern part of Halema‘uma‘u crater floor extending into the east wall of the downdropped block. Effusion rates appear down from initial eruptive rate, but remain high. Lava fountain heights have decreased since the eruption onset, but remain up to about 10-15 meters (32-50 feet) high this morning. Lava erupted from fissures on the downdropped block is flowing in a westward direction towards Halema‘uma‘u crater, covering much of the surface with active lava. The laser rangefinder is aimed at a western portion of Halema‘uma‘u crater, not near the new eruptive activity, and recorded about 2.5 m (8 feet) of new lava added to that portion of the crater floor. . A live-stream video of the eruption is available at Summit Observations: Summit tilt has remained deflationary over the past 24 hours. Summit seismic activity is dominated by eruptive tremor (a signal associated with fluid movement). Volcanic gas emissions in the eruption area are elevated; between 4 and 5 p.m. yesterday, HVO staff measured preliminary sulfur dioxide (SO2) emission rates of up to 100,000 tonnes per day or more. Emission rates appear to be lower this morning, but have not been confirmed by addtional measurments at this time. Rift Zone Observations: No unusual activity has been noted along the East Rift Zone or Southwest Rift Zone; steady rates of ground deformation and seismicity continue along both. Measurements from continuous gas monitoring stations downwind of Puʻuʻōʻō in the middle East Rift Zone—the site of 1983–2018 eruptive activity—remain below detection limits for SO2, indicating that SO2 emissions from Puʻuʻōʻō are negligible. Hazard Analysis: Eruptive activity is occurring on the downdropped block and Halemaʻumaʻu crater, within Kīlauea's summit caldera and in the closed area of Hawaiʻi Volcanoes National Park. During Kīlauea summit eruptions, the high level of volcanic gases—primarily water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2)—being emitted is the primary hazard of concern, as this hazard can have far-reaching effects downwind. As SO2 is released from the summit, it reacts in the atmosphere to create the visible haze known as vog (volcanic smog) that has been observed downwind of Kīlauea. Vog creates the potential for airborne health hazards to residents and visitors, damages agricultural crops and other plants, and affects livestock. For more information on gas hazards at the summit of Kīlauea, please see: Vog information can be found at Other significant hazards also remain around Kīlauea's summit from Halemaʻumaʻu crater wall instability, ground cracking, and rockfalls that can be enhanced by earthquakes within the area closed to the public. This underscores the extremely hazardous nature of the rim surrounding Halemaʻumaʻu crater, an area that has been closed to the public since early 2008. ---- Image Sources/Usage: Public Domain. An aerial view of the eruption at the summit of Kīlauea at approximately 6:30 a.m. HST on September 11, 2023. Multiple minor fountains remain active in the eastern portion of Halema‘uma‘u crater floor and on the downdropped block within Kīlauea's summit caldera. USGS photo by M. Patrick.

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