Hawaiian Volcano Update: Kīlauea Summit Eruption’s Episode 21 - May 15, 2025

In a Mother’s Day Sunday surprise, Kīlauea’s summit eruption remained on a shortened cycle to produce its 21st episode of lava flows and fountains on May 11, less than 5 days since its previous episode. Fountains reached maximum heights of about 650 feet or 200 meters, and produced a long lava flow along the northern caldera wall, until ceasing after nearly 8 hours of sustained fountaining and covering 50% of Halemaʻumaʻu crater floor. Precursory activity included intermittent fountains from 4:20 am, growing in frequency after 8 am, spilling its first lava onto the crater floor after 9:10 am, and beginning its continuous fountaining at 12:45 pm. Almost all of the output came from the north vent, with the south vent only activating with minor fountaining of less than 50 feet or 15 meters for the final few minutes of episode 21.

Dominant trade winds over the past week limited the impact of increased volcanic gas and tephra output, despite the massive volumes visibly produced during the highest output over the first 2 hours of the episode. Most of the fallout impacted the southwest sector of the caldera, which is closed to the public. Other overlooks within Hawaiʻi Volcanoes National Park provided spectacular views for visitors over the course of Motherʻs Day.

“Data indicate that episode 22 is likely to occur between Saturday and Sunday or in the next 2-3 days, with a small chance of being delayed until Monday” according to the USGS-HVO. While easterly winds are expected to return on Sunday, southeast winds possible on Friday and Saturday may allow the next episode to impact nearby communities through gas emissions and erupted material carried by the wind.  Vog and tephra hazards have become common to island residents, and the usual precautions and preparations apply, especially for those with respiratory sensitivities – more information at https://vog.ivhhn.org/.

Maunaloa continues to inflate quietly its established post-eruption pattern, with only small-magnitude earthquakes and minor adjustments evident on monitoring instruments. As usual, we summarize the monitoring signals, imagery, and reports for both volcanoes available courtesy of the USGS Hawaiian Volcano Observatory, annotating the presentation on screen as we go and discussing live viewer questions.