Photo & Video Chronology – September 17, 2025 – Kīlauea Summit Observations
Gas pistoning continued in the north vent and intermittently in the south vent. Small north vent overflows occurred at 8:38 AM and 8:59 AM HST during gas pistoning cycles. The new window for the start of episode 33 is Sept 17-20.
Cyclic rising and falling of the lava pond at the Halema‘uma‘u north vent was indicative of ongoing gas pistoning during the morning of September 17. Seismometers have tracked this gas pistoning since shortly after the end of Kīlauea summit eruptive episode 32 on September 2, but only in the past couple days has lava risen high enough for the cycles to be visible. This activity was observed by Hawaiian Volcano Observatory scientists on the western crater rim, which afforded an excellent view of the north vent. USGS photo by C. Cauley.
At 8:38 a.m. HST on September 17, the Halema‘uma‘u north vent overflowed for the first time in advance of Kīlauea summit eruptive episode 33. Shortly thereafter, lava drained deeper in the vent and the overflow stopped, but Hawaiian Volcano Observatory geologists visiting the western crater rim an hour later could clearly see its remains: a fresh, silvery lobe of pahoehoe on the northeast side of the north vent, within the channel structure that remains from episode 32 on September 2. USGS photo by M. Zoeller.