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USGS HVO Volcanic Activity Notice — Kīlauea RED/WARNING status change to ORANGE/WATCH

October 4, 2021

The USGS Hawaiian Volcano Observatory (HVO) is lowering Kīlauea’s volcano alert level to WATCH and its aviation color code to ORANGE, reflecting the less-hazardous nature of the ongoing eruption within Halemaʻumaʻu crater, in Kīlauea’s summit caldera and Hawai‘i Volcanoes National Park.

HVO/USGS Volcanic Activity Notice

Volcano: Kilauea (VNUM #332010)

Current Volcano Alert Level: WATCH
Previous Volcano Alert Level: WARNING

Current Aviation Color Code: ORANGE
Previous Aviation Color Code: RED

Issued: Monday, October 4, 2021, 4:52 PM HST
Source: Hawaiian Volcano Observatory
Notice Number: 2021/H273
Location: N 19 deg 25 min W 155 deg 17 min
Elevation: 4091 ft (1247 m)
Area: Hawaii

Volcanic Activity Summary: Kīlauea volcano is erupting. At approximately 3:21 p.m. HST on September 29, 2021, an eruption began within Halemaʻumaʻu crater, within Kīlauea’s summit caldera in Hawai‘i Volcanoes National Park. The USGS Hawaiian Volcano Observatory (HVO) elevated Kīlauea’s volcano alert level to WARNING and its aviation color code to RED to assess the intensity of eruptive activity and identify associated hazards.  

Vigorous fountaining—with bursts up to 50–60 meters (164–197 ft)—produced significant amounts of pumice, Peleʻs hair, and fragments of volcanic glass that were deposited in areas downwind along the rim and beyond Halemaʻumaʻu crater. Over the past several days, a thick layer (approximately 27 meters or 89 ft) of molten lava has accumulated as a lava lake at the base of the crater, partially drowning the vents resulting in subdued fountaining. During the same time, the amount of sulfur dioxide (SO2) emitted has dropped from 85,000 tons per day (one metric ton equals 2,200 pounds) to 12,000 tons a day. Although the amount of gas and volcanic particle production has decreased since the eruption onset, they both remain significant local hazards within the plume. Concentrations of SO2 at the vents remain high (likely over 100 parts per million or ppm) and significantly elevated (5-10 ppm) at stations a few kilometers (a couple of miles) southwest of Halemaʻumaʻu.

The eruption is currently confined to Halemaʻumaʻu crater, within Hawai‘i Volcanoes National Park.  HVO does not see any indication of activity migrating elsewhere on Kīlauea volcano  and expects the eruption to remain confined to the summit region.

HVO is lowering Kīlauea’s volcano alert level to WATCH and its aviation color code to ORANGE, reflecting the less-hazardous nature of the ongoing eruption. 

For more information on gas hazards at the summit of Kīlauea, please see:

For more information about volcanic ash hazards and precautions at Kīlauea, please see:

Recent Observations:
[Volcanic cloud height] 1000–2000 meters (3280–6562 ft)
[Other volcanic cloud information] Plume composed of SO2 and H2O with minor volcanic particles
[Lava flow/dome] None.
[Ballistics] None.
[Lava flow] Active fissures feeding lava lake at bottom of Halemaʻumaʻu crater, Kīlauea summit

Remarks: Prognosis: 

It is unclear how long the current eruption will continue. Kīlauea summit eruptions over the past 200 years have lasted from less than a day to more than a decade. This ongoing eruption is similar to the most recent Kīlauea eruption, which was also confined to Halemaʻumaʻu crater and generated a lava lake; the most recent eruption lasted approximately five months, from December 2020 to May 2021. 

HVO is in constant communication with the National Park Service and Hawai‘i County Civil Defense and other agencies responsible for public safety. 

HVO scientists will continue to monitor Kīlauea volcano closely and will issue additional messages as warranted by changing activity. Stay informed about Kīlauea by following volcano updates and tracking current monitoring data on the HVO web page at

More Information:
Kīlauea activity summary also available by phone: (808) 967-8862
Kīlauea webcam images:
Kīlauea photos/video:
Kīlauea lava-flow maps:
Kīlauea FAQs:

Hazard Analysis: 

This new eruption at Kīlauea’s summit is occurring within a closed area of Hawaiʻi Volcanoes National Park. Therefore, high levels of volcanic gas and fine volcanic particles are the primary hazards of concern, as these hazards can have far-reaching effects downwind.

Large amounts of volcanic gas—including carbon dioxide (CO2) and sulfur dioxide (SO2)—are continuously released during eruptions of Kīlauea volcano. Concentrations of SO2 can be much greater than recommended exposure levels on Halemaʻumaʻu rim and extending several kilometers downwind; exposure to these elevated SO2 levels is considered hazardous and may cause breathing difficulties. Additional hazards include Pele's hair and other lightweight volcanic glass fragments from the lava fountains that can be entrained in the plume and fall several kilometers (miles) downwind of the fissure vents.

Strong winds may waft lighter particles to greater distances and impact surrounding communities. Residents should minimize exposure to fine volcanic particles, which can cause skin and eye irritation.  As the SO2 plume moves away from the vent, it reacts in the atmosphere to create the visible haze known as vog (volcanic air pollution) 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 caldera from Halemaʻumaʻu crater wall; ground instability, ground cracking, and rockfalls can be enhanced by earthquakes within the area closed to the public. This underscores the extremely hazardous nature of Kīlauea caldera rim surrounding Halemaʻumaʻu crater, an area that has been closed to the public since late 2007.  

For discussion of Kīlauea hazards, please see:

Please see the Hawaiʻi Volcanoes National Park website for visitor information: Visitors to Hawaiʻi Volcanoes National Park should note that under southerly (non-trade) wind conditions, there is potential for ashfall—a dusting of powdery to gritty ash composed of volcanic glass and rock fragments. These ashfalls represent a minor hazard, but visitors should be aware that dustings of ash at areas around the Kīlauea summit are possible.  


Next Notice: The Hawaiian Volcano Observatory (HVO) continues to closely monitor Kīlauea's seismicity, deformation, and gas emissions for any changes in activity. Kīlauea updates will be issued daily. Should volcanic activity change significantly a new VAN will be issued. Regularly scheduled updates are posted at

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Recent earthquakes in Hawaiʻi (map and list):

Explanation of Volcano Alert Levels and Aviation Color Codes:

The Hawaiian Volcano Observatory is one of five volcano observatories within the U.S. Geological Survey and is responsible for monitoring volcanoes and earthquakes in Hawaiʻi.

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