Traverse-based sulfur dioxide emission rates from Hawaiian volcanoes, 2023–2025

Sulfur dioxide (SO2) emission rates are a fundamental measurement for the study and monitoring of active volcanoes. Such emissions inform scientists about the level of volcanic activity or unrest, and they also present a hazard to surrounding populations. Here we present a continuation of a long-term dataset collected by the Hawaiian Volcano Observatory for over four decades using UV spectrometers in below-plume traverses [Casadevall and others, 1987; Elias and others, 1998; Elias and Sutton, 2002; Elias and Sutton, 2007; Elias and Sutton, 2012; Elias and others, 2018a; Elias and others, 2018b; Elias and others, 2020; Kern and others, 2020; Nadeau and others, 2023]. Traverse-based emission rate measurements included herein were compiled between 2023 and 2025 and span six eruptions at Kīlauea, as well as the quiescent periods between eruptions. No SO2 emission rate measurements were made at other Hawaiian volcanoes (e.g., Mauna Loa) during the timeframe of this data release; only Kīlauea was emitting SO2 in quantities measurable by UV spectrometer.

The dataset begins with measurements obtained during the January 2023 summit eruption of Kīlauea. SO2 emissions remained elevated as the eruption persisted into March; following the end of the eruption, emissions dropped to background (~100 tonnes/day, or t/d) until the onset of the June 2023 summit eruption. Again, increased SO2 emissions persisted through to the end of the roughly two-week eruption. SO2 emission rates dropped to background once more, and remained low until the September 2023 summit eruption, which lasted only one week. No additional eruptive activity occurred in 2023. In June 2024, however, the first eruption in 50 years on Kīlauea’s Southwest Rift Zone (SWRZ) took place over the course of approximately nine hours. Unlike most prior eruptions, including those in 2023 included here, SO2 emissions remained elevated for a few days following the end of lava effusion. The next eruption took place over the course of roughly one week in September, on Kīlauea’s Middle East Rift Zone (MERZ), in and near Nāpau Crater. For the duration of the eruption, SO2 emissions varied with the intensity of eruptive activity, but were very low by the end of the eruption and no longer detectable just a few days later. The final portion of this data release covers the December 2024 summit eruption, which, after an initial few days of fissure-based activity, established itself as a prolonged, episodic lava fountain eruption, with pauses on the order of days to weeks between episodes. As such, associated emission rates are variable: all emission rates are above background, but fountaining events emitted tens of thousands of tonnes per day of SO2 while inter-episode emissions were typically over an order of magnitude less. Also adding to the variability of the measured emission rates was the presence of gas pistoning cycles [e.g., Nadeau and others, 2015; Patrick and others, 2016] during many of the pauses from mid-March 2025 onward.

In this data release, we include raw spectra collected by ultraviolet (UV) spectrometers on traverses beneath SO2 plumes, derived SO2 emission rates and associated metadata for each individual traverse, and means of SO2 emission rates for each separate traverse campaign/set of traverses. Data are separated by the three eruption sites/degassing locations: Kīlauea summit (Halemaʻumaʻu), Kīlauea MERZ (Nāpau Crater), and Kīlauea SWRZ.



References

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