The USGS Hawaiian Volcano Observatory conducted the monitoring overflight of Halema‘uma‘u crater the morning of December 2, 2025. With permission from Hawai‘i Volcanoes National Park, scientists visited the crater floor to collect a sample of episode 37 lava and to take visual/thermal imagery that will allow us to map the distribution of material erupted during episode 37 (lava flows and tephra). Lava fountained only from the north vent during episode 37, for about 9 hours on November 25. The summit region of Kīlauea volcano has shown inflationary deformation since the end of episode 37, suggesting that another eruptive episode is possible. USGS video by K. Mulliken. 

During a USGS Hawaiian Volcano Observatory monitoring overflight the morning of December 2, 2025, geologists were able to see a spattering lava surface deep within the north vent. The yellow material around the vents is native sulfur. Continued degassing from the vents at the summit of Kīlauea volcano produces native sulfur when sulfur dioxide and hydrogen sulfide gases react and cool upon reaching the surface.  USGS video by K. Mulliken. 

An aerial view of the north (right) and south (left) vents in Halema'uma'u, taken during a USGS Hawaiian Volcano Observatory monitoring overflight the morning of December 2, 2025. Both vents were actively degassing, and a spattering lava surface was visible deep within their conduits.  USGS photo by D. Downs

This black solidified lava channel is a stark contrast to the weathered brown walls of Halemaʻumaʻu crater nearby. The lava channel transported lava from the north vent, along the north rim of the crater, allowing lava flows to reach the farthest regions of the crater to the east during the 9 hours of lava fountaining of episode 37 on November 25, 2025. USGS photo by K. Mulliken.

The north and south vents were degassing during a USGS Hawaiian Volcano Observatory monitoring overflight of Kīlauea summit on December 2, 2025. Eruptive activity at these vents was paused on December 2, following 9 hours of lava fountaining during episode 37 on November 25, but a spattering lava surface was visible deep within both vents. USGS photo by K. Mulliken. 

This aerial photograph, taken during a USGS Hawaiian Volcano Observatory monitoring overflight the morning of December 2, 2025, shows volcanic gas wafting over the tephra-blanketed rim of Halemaʻumaʻu crater. The ripple-like deposits on the right side of the image, on the crater rim, are spatter-fed lava flows that formed during episode 34 on October 1. Enough lava from the fountaining landed on the crater rim during episode 34, to accumulate and flow a short distance. This was the only lava flow on the crater rim so far in this eruption. USGS photo by K. Mulliken. 

The USGS Hawaiian Volcano Observatory often gets asked how long it will take the lava flows to fill in Halemaʻumaʻu crater and spill onto the upper caldera floor of Kīlauea. This photo, taken from the floor of the crater, shows the lava flows from episode 37 (November 25) where they contact the north wall of the crater, which rises several hundred feet above.  On average, lava flows at the base of Halemaʻumaʻu have an elevation of 3219 feet (981 meters) above sea level (as of November 25, after episode 37), while the northeastern part of Kaluapele (Kīlauea summit caldera) above it is at an elevation of about 3500 feet (1067 meters) above sea level. This means that an addition 300 feet (91 meters) of lava will need to fill the crater before lava flows spill onto the upper caldera floor. USGS photo by K. Mulliken. 

The steaming north wall of Halemaʻumaʻu crater wall rises several hundred feet above the lava flows that cover the floor of the crater.  On average, lava flows at the base of Halemaʻumaʻu have an elevation of 3219 feet (981 meters) above sea level (as of November 25, after episode 37), while the northeastern part of Kaluapele (Kīlauea summit caldera) above it is at an elevation of about 3500 feet (1067 meters) above sea level. USGS photo by K. Mulliken.