USGS Scientists Race to Sample Kilauea Crater Deposits Before Lava Buries Them Forever

A Narrow Window Into Volcanic History

It was a mission with a ticking clock. On July 2, a team of federal scientists descended by helicopter into one of the most geologically dynamic places on Earth — the crater of an actively erupting Hawaiian volcano — to collect samples that may soon be gone forever. Three USGS Hawaiian Volcano Observatory scientists flew via helicopter to the northwest side of Halema'uma'u at the summit of Kīlauea to sample tephra deposits in the crater wall. The window to do so is closing fast.

These deposits were exposed by the 2018 summit collapse, but lava flows from the ongoing episodic Kīlauea summit eruption are likely to bury them again in the near future. Scientists recognized that if they didn't act now, these geological records — preserved in the crater wall for years — could be entombed under fresh lava, potentially for decades or longer.

What Is Tephra, and Why Does It Matter?

Tephra is the general name given to anything thrown into the air during a volcanic eruption. It can range from individual ash particles all the way to volcanic bombs, according to the USGS. These layered deposits act like pages in a geological diary, preserving a record of past eruptions — their intensity, their chemistry, and the conditions under which they occurred.

Physical and geochemical study of these samples will hopefully improve scientists' understanding of Kīlauea's long-term eruptive history, especially the magmatic processes associated with explosive eruptions at the volcano. That kind of knowledge isn't just academically interesting — it directly informs hazard assessments for the communities living in the shadow of one of the world's most active volcanoes.

How Rising Lava Made the Mission Possible

The remarkable irony of this mission is that the very eruptions threatening to bury these deposits are also what made them accessible in the first place. As lava flows have filled in Halema'uma'u during the eruptions of Kīlauea, the floor of the crater has risen, making it possible for scientists to walk across it. Deposits that were once halfway up a sheer cliff face are now reachable by helicopter — and even on foot in some areas.

The Hawaiian Volcano Observatory noted that the refilling of the crater by eruptions since 2020, including the ongoing lava fountaining episodes, made it "fairly easy to access the deposits, which just a few years ago were halfway up the cliff." The July 2 mission to the northwest side of Halema'uma'u crater was done with permission from and coordination with Hawai'i Volcanoes National Park. That coordination reflects the careful balance required when conducting scientific fieldwork inside an active national park that is itself in a constant state of volcanic transformation.

An Eruption That Keeps on Going

Kīlauea has seen 50 eruptive episodes since December 23, 2024. The pace of activity has been relentless, with each fountaining episode reshaping the crater floor and steadily raising the elevation of the lava lake. The vent structure that has built up in Halema'uma'u is approaching the elevation of the crater rim, but several hundred feet remain between it and the top of the tephra cone built up on the crater rim by the fountaining episodes since December 2024.

The samples collected on July 2 now head to the laboratory, where researchers will analyze their physical structure and chemical composition. The results could shed new light on the deep magmatic plumbing that has powered Kīlauea's explosive past — and help scientists better anticipate what this restless volcano might do next. As the crater floor continues to rise and lava inches ever closer to those ancient tephra walls, the July 2 mission may prove to be one of the last chances scientists ever had to read that particular chapter of Kīlauea's long, fiery story.