Hawaiian Volcano Update: Kīlauea’s South Caldera Quaking

This past week, earthquakes on Kīlauea concentrated beneath the south caldera area, though only reached magnitude 2.6 despite the region exhibiting accelerated inflation for 3 weeks. Seismic counts across the whole volcano exceeded 100 events yesterday, similar to the previous cycle peak on March 31st but above the average last week of around 50 events per day. However, these numbers are still low compared to the main pulse of magma intrusion into the Southwest Rift in late January and early February, when over 3,000 events occurred within one week. For now, the volcano continues to recharge and pressurize, building towards its next possible eruption.

Volcanic gas emissions, the main current threat to residents and visitors, remain relatively low around 60 tonnes of SO2 per day, though are still a concern for sensitive individuals nearby. Maunaloa is also still quiet with few earthquakes and sustained slow inflation as it recharges with magma, and remains at the lowest USGS warning level.

As usual we review the monitoring signals, imagery and reports available courtesy of the USGS Hawaiian Volcano Observatory, annotating the presentation on screen as we go and discussing live viewer questions. We also reprise a short summary of the events of March 27 to April 11, 1868, which included two eruptions on Maunaloa, two eruptions on Kīlauea, caldera collapses at both volcanoes, the largest earthquake ever felt in Hawaiʻi at magnitude 7.9 and two others of magnitude 7, landslides and cliff collapses, and two sequences of tsunamis all within 16 days. Despite some uncertainty in the details, this sequence of events comprises a worst-case scenario for which our island communities must prepare.

As a bonus this week, we present a shortened recap and review of the USGS presentation on “A Brief History of Kīlauea’s Southwest Rift Zone” from Volcano Awareness Month in January 2024.