Volcano Hazards Program Office

Shaded relief map of Henrys Fork Caldera and vicinity. The margin of Henrys Fork Caldera is shown in blue. Note the smooth, low-relief topography within the caldera compared to the steep and dynamic topography associated with Yellowstone Caldera (at the right side of the image).

Lava continues to erupt from the west vent in Halema‘uma‘u, at the summit of Kīlauea. Low lava fountains of only a few meters (yards) tall were common on October 25, with higher bursts sometimes reaching up to 12 meters (39 ft). The cone was measured at 25 meters (82 ft) above the active lava lake surface. Lava ponded inside the cone flows down the spillway—which is about

Eruptive activity continues in Halema‘uma‘u crater, at the summit of Kīlauea. The west vent remains active with low fountaining in a slightly perched pond set within the cone. Lava pours through a short spillway into the lava lake.

This photo from the northwest rim of the caldera shows the western vent supplying lava into the lake in Halema‘uma‘u crater, at the summit of Kīlauea. A portion of the lake margin (bottom left in photo) is formed by a perched levee. USGS photo by M. Patrick.

A wider view of the lava lake in Halema‘uma‘u crater, at the summit of Kīlauea. Active surface lava remains mostly limited to the western side of the lake (right side in this photo). The western vent continues to have low fountaining set within the cone. USGS photo by M. Patrick.

Eruptive activity continues in Halema‘uma‘u crater, at the summit of Kīlauea. The west vent remains active with low fountaining in a slightly perched pond set within the cone. Lava pours through a short spillway into the lava lake. USGS image by M. Patrick.

Morning views of the eruption within Halema‘uma‘u crater, at Kīlauea summit, on October 23, 2021. This view is from the south rim of the crater. Variable west vent fountain heights are visible in this video, which is shown at 5 times speed. Sporadic foundering, when cooler lava crust on the surface sinks back into the liquid portion of the lava lake below, is also visible

Morning views of the eruption within Halema‘uma‘u crater, at Kīlauea summit, on October 23, 2021. This view is from the south rim of the crater. Lava continues to erupt from a single vent on the western wall of the crater. Lava fountains within the cone and spills out of the cone opening, flowing east into the lake. 

A view of Halema‘uma‘u crater, at the summit of Kīlauea volcano, just after 6 a.m. HST on Saturday, October 23. Lava continues to erupt from the west vent into the lava lake at the base of the crater. Surface activity is limited to the west portion of the lake. USGS photo by K. Mulliken.

Lava exits the west vent in Halema‘uma‘u crater the morning of October 23, 2021. Simultaneously, lava fountaining at the vent is vigorous enough to send spatter up, over, and onto the outer margin of the cone. This process, spatter accumulation, is how the cone around the west vent formed and continues to grow. USGS photo by K. Mulliken.

Morning views of the eruption within Halema‘uma‘u crater, at Kīlauea summit, on October 23, 2021. Variable west vent fountain heights are visible in this video, which is shown at 5 times speed. Sporadic foundering, when cooler lava crust on the surface sinks back into the liquid portion of the lava lake below, is also visible across the active west portion of the lava lake