Characterising the wind-advected medial fall deposit from fissure 8 fountaining during the 2018 lower East Rift Zone eruption, Kīlauea
Characterising the wind-advected medial fall deposit from fissure 8 fountaining during the 2018 lower East Rift Zone eruption, Kīlauea
The 2018 eruption on the lower East Rift Zone, Hawaii, involved the opening of 24 fissures before the eruption focussed on a single point source, fissure 8 (F8). This study characterises the preserved medial F8 tephra deposit using an isopach map, maximum clast size data, and total grain size distribution analysis, shedding light on the tephra transport and dispersal mechanisms beyond the F8 cone occurring during the fountaining. The medial sheet-like deposit covers approximately 0.22 km2, best fit by a Power-Law thinning rate. The TephraFits model estimated the corresponding volume of the continuous medial tephra blanket to be ~ 2 × 104 m3, just 0.02% of the total volume erupted from fissure 8. Samples from the preserved medial deposit have grain size modes of − 3.5 to − 4 Φ, compatible with Voronoi tessellation calculations. Maximum clast size did not show a ‘typical’ fining relationship with distance from the vent; instead, it shows no clear pattern. One factor was that the extremely low clast density, a function of a secondary vesiculation event, enabled the pyroclasts to be re-entrained, often repeatedly, by large eddies downwind of the vent. This should be considered in future studies of prolonged fountaining episodes as the clasts involved in the medial fall are rarely well preserved in the geologic record due to their fragile nature but their presence adds complexity to the inferred eruption dynamics.
Grain size, Hawaiian Fountaining, lower East Rift Zone, Reticulite, Tephra deposit, Vesicularity
Watts, Emma J.
2135079d-2472-4d7e-a05a-3f234793697e
Cockshell, Wendy A.
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Houghton, Bruce F.
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Watts, Emma J.
2135079d-2472-4d7e-a05a-3f234793697e
Cockshell, Wendy A.
0cc2ebcd-b45e-4789-af84-8dbfd73d0cba
Houghton, Bruce F.
32fca8af-e616-490e-af5f-99353567ba51
Watts, Emma J., Cockshell, Wendy A. and Houghton, Bruce F.
(2023)
Characterising the wind-advected medial fall deposit from fissure 8 fountaining during the 2018 lower East Rift Zone eruption, Kīlauea.
Bulletin of Volcanology, 85 (10), [51].
(doi:10.1007/s00445-023-01668-7).
Abstract
The 2018 eruption on the lower East Rift Zone, Hawaii, involved the opening of 24 fissures before the eruption focussed on a single point source, fissure 8 (F8). This study characterises the preserved medial F8 tephra deposit using an isopach map, maximum clast size data, and total grain size distribution analysis, shedding light on the tephra transport and dispersal mechanisms beyond the F8 cone occurring during the fountaining. The medial sheet-like deposit covers approximately 0.22 km2, best fit by a Power-Law thinning rate. The TephraFits model estimated the corresponding volume of the continuous medial tephra blanket to be ~ 2 × 104 m3, just 0.02% of the total volume erupted from fissure 8. Samples from the preserved medial deposit have grain size modes of − 3.5 to − 4 Φ, compatible with Voronoi tessellation calculations. Maximum clast size did not show a ‘typical’ fining relationship with distance from the vent; instead, it shows no clear pattern. One factor was that the extremely low clast density, a function of a secondary vesiculation event, enabled the pyroclasts to be re-entrained, often repeatedly, by large eddies downwind of the vent. This should be considered in future studies of prolonged fountaining episodes as the clasts involved in the medial fall are rarely well preserved in the geologic record due to their fragile nature but their presence adds complexity to the inferred eruption dynamics.
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s00445-023-01668-7
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e-pub ahead of print date: 5 September 2023
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Funding Information:
We gratefully acknowledge the contribution of Tristan Helzer, Matthew Patrick, and Thorvaldur Thordarson for their assistance in the field. We are also thankful to a 2022 graduate class (ERTH601) at the University of Hawaii at Manoa, who aided in the data acquisition. We thank two anonymous reviewers and the Associate Editor, Tomaso Esposti Ongaro, for their constructive comments. The research was partially supported by grants from the Royal Geographical Society [PRA 11.22]; the Volcanic and Magmatic Studies Group, UK; the Geological Society of London; the U.S. Geological Survey; and the United States National Science Foundation [EAR 1829188].
Publisher Copyright:
© 2023, The Author(s).
Keywords:
Grain size, Hawaiian Fountaining, lower East Rift Zone, Reticulite, Tephra deposit, Vesicularity
Identifiers
Local EPrints ID: 482163
URI: http://eprints.soton.ac.uk/id/eprint/482163
ISSN: 0258-8900
PURE UUID: fe3c3c1e-cd92-41cf-a0a8-3e3cc002144a
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Date deposited: 20 Sep 2023 16:45
Last modified: 27 Apr 2024 02:22
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Author:
Emma J. Watts
Author:
Wendy A. Cockshell
Author:
Bruce F. Houghton
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