Kīlauea Lava Lake Continues to Rise

September 30, 2021, 3:13 PM HST
* Updated October 1, 3:41 AM
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Kīlauea’s lava lake has been rising approximately one meter (yard) an hour since the eruption began, Wednesday afternoon according to a US Geological Survey (USGS) update released Thursday.

The initial vents of the new Kīlauea summit eruption appeared on the central crater floor Wednesday, Sept. 29, at about 3:20 p.m. Just after 4:40 p.m., a new vent opened on the west wall of the Halemaʻumaʻu crater. The dominant fountain south of the lake center, reportedly reached a height of a five-story building.

Lava continues to erupt from multiple vents along the floor and western wall of Halemaʻumaʻu crater, USGS reports. As of Thursday afternoon, all lava activity is confined within Halemaʻumaʻu Crater. Seismicity and volcanic gas emission rates remain elevated.

There are some effects from vog (volcanic fog) in the surrounding areas, and some bits of volcanic ash and rock may fall downwind within the Volcanoes National Park, but the communities around the volcano are safe.



The lava lake has been rising approximately one meter (yard) an hour since the eruption began, according to the USGS update.

The lava lake has not exhibited widespread circulation overnight, with localized and discontinuous areas of crustal foundering (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).

The maximum fountain height so far, observed Wednesday, was estimated to be 82-98 feet high, though most fountains are currently only yards high.


Summit Observations: Sulfur dioxide emission rates remain high and were estimated at around 85,000 tonnes per day just after the eruption started. Seismicity is elevated but stable, with few earthquakes and ongoing volcanic tremors. Summit tiltmeters continued to record slowing deflationary tilt through this afternoon.

No unusual activity has been noted in the Kīlauea East Rift Zone. Ground deformation motion suggests that refilling of the upper East Rift Zone—between the summit and Puʻuʻōʻo — may have slowed slightly since the recent August intrusion. SO2 and hydrogen sulfide (H2S) emissions from Puʻuʻōʻō were below instrumental detection levels when last measured on January 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 the eruptions of the 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.

For more information on gas hazards at the summit of Kīlauea, click here.

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, ground cracking, and rockfalls that 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, click here.


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