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Published October 24, 2019 | Supplemental Material + Published
Journal Article Open

Understanding Degassing Pathways Along the 1886 Tarawera (New Zealand) Volcanic Fissure by Combining Soil and Lake CO₂ Fluxes

Abstract

CO₂ flux measurements are often used to monitor volcanic systems, understand the cause of volcanic unrest, and map sub-surface structures. Currently, such measurements are incomplete at Tarawera (New Zealand), which erupted with little warning in 1886 and produced a ∼17 km long fissure. We combine new soil CO₂ flux and C isotope measurements of Tarawera with previous data from Rotomahana and Waimangu (regions also along the 1886 fissure) to fingerprint the CO₂ source, understand the current pathways for degassing, quantify the CO₂ released along the entire fissure, and provide a baseline survey. The total CO₂ emissions from the fissure are 1227 t⋅d⁻¹ (742–3398 t⋅d⁻¹ 90 % confidence interval), similar to other regions in the Taupō Volcanic Zone. The CO₂ flux from Waimangu and Rotomahana is far higher than from Tarawera (>549 vs. ∼4 t⋅d⁻¹ CO₂), likely influenced by a shallow silicic body at depth and Okataina caldera rim faults increasing permeability at the southern end of the fissure. Highly localized regions of elevated CO2 flux occur along the fissure and are likely caused by cross-cutting faults that focus the flow. One of these areas occurs on Tarawera, which is emitting ∼1 t⋅d⁻¹ CO₂ with a δ¹³CO₂ of −5.5 ± 0.5 ‰, and comparison with previous observations shows that activity is declining over time. This region highlights the spatial and temporal complexity of degassing pathways at volcanoes and that sub-surface structures exert a primary control on the magnitude of CO₂ flux in comparison to the surface mechanism (i.e., CO₂ released through the soil or lake surface).

Additional Information

© 2019 Hughes, Mazot, Kilgour, Asher, Michelini, Britten, Chardot, Feisel and Werner. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Received: 25 May 2019; Accepted: 24 September 2019; Published: 24 October 2019. Data Availability Statement: All datasets generated and analyzed for this study are included in the manuscript/Supplementary  Materials. Author Contributions: EH, AM, and GK contributed the conception and design of this study. CA and EH collected the photogrammetry data. CA processed the orthophotos. EH, AM, GK, CA, MM, KB, LC, and YF collected the Tarawera CO₂ flux data. EH processed the CO₂ flux data with the help of AM. EH wrote the first draft of the manuscript. All authors contributed to manuscript revision, read, and approved the submitted version. EH was funded during an internship by GNS Science, NERC GW4+ DTP, and a GNS Science/NERC GW4+ DTP Ph.D. studentship [NE/L002434/1]. AM and GK are supported by the New Zealand Strategic Science Investment Fund (SSIF) from the New Zealand Ministry of Business, Innovation & Employment (MBIE). The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. We would like to thank the Ruawahia 2B trust for welcoming us onto Mount Tarawera and permitting us to collect data on the mountain and especially Ken Raureti, Tīpene Marr, and Paul Warbrick for their support of this work; Andy Phillips (GNS Science) who ran the Tarawera δ¹³CO₂ analyses; and we also thank Colin Wilson, Dmitri Rouwet, and Valerio Acocella for their constructive and helpful comments, and Artur Ionescu for their editorial handling. Supplementary Material: The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/feart.2019.00264/full#supplementary-material

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Created:
August 19, 2023
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October 18, 2023