Rate of Lava Lake Rise Decreases as Eruption Continues at Kīlauea

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At Kīlauea Volcano, lava continues to erupt within Halemaʻumaʻu Crater.

However, the number of active fountaining locations at the base and on the west wall of the crater has decreased just two days since the eruption began, and the rate of lava lake rise has slowed, the US Geological Survey reported Friday, Oct. 1.

The current volcano alert level is “warning” and the aviation color code is “red.”

Since the eruption began on Wednesday, Sept. 29, the lava lake surface has risen 79 feet. As of Friday morning, all lava activity remains confined within Halemaʻumaʻu, in Hawai’i Volcanoes National Park. Seismicity and volcanic gas emission rates remain elevated.

Over the past 24 hours, the lava lake surface has risen approximately 4.4 yards. In total, the lava lake surface has risen approximately 26 yards since the eruption started. Localized and discontinuous crustal foundering continues (a process by which cool lava crust on the surface of the lava lake is overridden by less-dense liquid from below, causing the crust to sink into the underlying lake lava).


Thursday night, field crews reported maximum fountain heights of 49 feet at the dominant vent on the west wall of Halemaʻumaʻu. Low fountaining continues at other sources, which are less vigorous.

Sulfur dioxide (SO2) emission rates remain high and were estimated at around 20,000 tonnes per day the morning of Thursday Sept. 30. This is significantly lower than the initial emission rates of 85,000 tonnes per day that were measured just after the eruption started on Wednesday afternoon. Seismicity is stable, with few earthquakes and ongoing eruptive tremors. Summit tiltmeters continued to record slowing deflationary tilt through the last 24 hours.

No unusual activity has been noted in the Kīlauea East Rift Zone. Ground deformation motion suggests that the upper East Rift Zone — between the summit and Puʻuʻōʻo — has been steadily refilling with magma over the past year. SO2 and hydrogen sulfide (H2S) emissions from Puʻuʻōʻō were below instrumental detection levels when last measured on Jan. 7, 2021.

This new eruption at Kīlauea’s summit is occurring within a closed area of Hawai’i Volcanoes National Park. Therefore, high levels of volcanic gas are the primary hazard of concern, as this hazard can have far-reaching effects downwind.


Large amounts of volcanic gas — primarily water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2) — are continuously released during eruptions of Kīlauea Volcano. 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, see:

Vog information can be found at

Additional hazards include Pele’s hair and other lightweight volcanic glass fragments from the lava fountains that will fall downwind of the fissure vents and dust the ground within a few hundred meters (yards) of the vent(s). Strong winds may waft lighter particles to greater distances. Residents should minimize exposure to these volcanic particles, which can cause skin and eye irritation.


Other significant hazards also remain around Kīlauea caldera from Halemaʻumaʻu crater wall instability, including 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 Kīlauea caldera rim surrounding Halemaʻumaʻu crater, an area that has been closed to the public since late 2007.

For discussion of Kīlauea hazards, see:

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