Halema‘uma‘u eruption: Hawaiian Volcano Observatory works closely with UH Hilo geology lab to quickly analyze eruption samples

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Lava samples collected September 11 were driven from the eruption to the UH Hilo geology lab, where undergraduate geology research assistants immediately started sample preparation and analysis.

Lava field with eruption in background. Two scientists are collecting lava in the foreground.
Hawaiian Volcano Observatory geologists collect a molten lava sample near the erupting vents during the morning of September 11, 2023. The samples were quickly taken to a geology laboratory at UH Hilo for analysis. (USGS photo by M. Patrick)

Volcano Watch is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates. This article and photos were published on September 14, 2023.  

Kīlauea eruptions in 2020–2021, 2021–2022, January–March 2023, and June 2023 started and remained within Halema‘uma‘u crater. The newest eruption that began Sunday, September 10, 2023, also started as a lava fountain bursting from within Halema‘uma‘u.

Student in lab.
UH Hilo undergraduate research assistant Paige Johnson places a sample of the Kīlauea summit eruption into the shatterbox, which will turn the sample into a homogenous powder. (Photo: Steve Lundblad/UH Hilo Department of Geology)

However, in the minutes to hours immediately following eruption start, vents opened to the east, on the downdropped block that lowered during the 2018 summit collapse. This represents the first lava that has erupted within the summit caldera, but out of Halema‘uma‘u, in 41 years! In 1982, there were two summit eruptions, both lasting less than one day, that occurred outside of Halema‘uma‘u.

Since the 2018 summit collapse, eruptions have slowly filled in Halema‘uma‘u. In fact, the eastern rim of Halema‘uma‘u is nearly covered with flows originating from the downdropped block. These lava flows are more accessible than those produced during earlier eruptions and geologists were able to collect a molten sample of lava from close to an erupting vent.

HVO works closely with partners at the University of Hawai‘i at Hilo to quickly analyze eruption samples. What does a day in the life of a lava sample look like as it makes its way from the volcano to ultimately providing information about the nature of the eruption?

When they collect a hot and molten lava sample, HVO scientists quench (cool) it in water. The sample collected on September 11 was driven from the eruption to UH Hilo, where undergraduate geology research assistants immediately started sample preparation and analysis. First, they dried the sample by putting it in a warm oven for two hours.

Student working on lava sample in lab.
UH Hilo geology major Paige Johnson compresses a lava sample, collected by Hawaiian Volcano Observatory scientists during the ongoing Kīlauea summit eruption, into a solid pellet that can be analyzed. (Photo: Steve Lundblad/UH Hilo Department of Geology)
Round pale disc next to a Sharpie pen for scale.
A photo showing what a completed pellet looks like, with a sharpie pen for scale. The rough and uneven lava sample has been transformed into a pellet that is dense, fine-grained, and has a flat surface that can be analyzed. (Photo: Steve Lundblad/UH Hilo Department of Geology)

In the early afternoon, a portion of the dried sample was pulverized in a paint-shaker like device called a shatterbox. This process turns the rock into a homogenous powder. The powder was then compressed into a pellet under 25 tons of pressure. The pellet provides a dense, fine-grained, flat surface that can be analyzed for its bulk composition in an instrument called an Energy Dispersive X-Ray Fluorescence Spectrometer (EDXRF), which takes only 20 minutes to complete.

EDXRF uses a small portion of sample, leaving most of the rock for other types of analyses. The chemical composition provided by EDXRF gives a first glimpse of what is happening with the magma during the eruption. Analysis of the sample collected the morning of September 11 was completed less than 24 hours after the eruption began!

In the lab: Machine on left with computer screen on right showing graph lines.
After preparing the lava samples, the pressed pellets are loaded into the energy dispersive x-ray fluorescence (ED-XRF) instrument for analysis (box on the left in the image). The computer screen shows the spectral spikes for certain elements measured in the sample during the analysis. These compositional analyses are used by HVO and UH Hilo partners to understand the eruption. The lava samples for this eruption so far have about 6.8 weight percent MgO (magnesium oxide), which is nearly identical to previous Kīlauea summit eruptions since 2020. (Photo: Steve Lundblad/UH Hilo Department of Geology)

Rapid analyses of eruption samples provides valuable information to track eruptions at Kīlauea. The high-quality geochemical characterization that EDXRF analyses offer in near-real-time allows HVO and UH Hilo geologists to track daily changes in lava chemistry. The partnership between HVO and UH Hilo began several years before the devastating 2018 lower East Rift Zone eruption but was put to the test during that eruption.

Knowing the compositional changes in the lava samples the very same day they erupted proved critical to understanding changes in lava flow behavior as the 2018 eruption transitioned from cooler, sluggish lava, to hotter, faster-moving lava. This was a valuable tool in assessing the hazard to properties from the advancing lava flows.

Processing eruption samples in a timely manner takes a team. Working together, HVO and UH Hilo have learned that the temperature and chemistry of lava erupted during this new eruption look very similar to lava from the past four eruptions. This suggests that even if hotter magma from a deeper source is moving into the volcano, it is continuing to mix and cool in a shallower magma body before reaching the surface.

At HVO, scientists collect samples, and other important data about the eruption. At UH Hilo, faculty and students prepare and analyze the samples. They work together to interpret the compositional data and learn about the processes associated with recent eruptions at Kīlauea.

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