Flowage of the 1991 Unzen lava; discussions to   ‘Rigid migration of Unzen lava rather than flow’ J. Volcanol. Geotherm. Res., 110, 107073

Sato, H.; Suto, Shigeru; Ui, Tadao; Fujii, Toshitsugu; Yamamoto, Takahiro; Takarada, Shinji; Sakaguchi, Kei

doi:10.1016/j.jvolgeores.2021.107343

Cited by 4 publications

(1 citation statement)

References 27 publications

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“…In five years, the eruption generated 2.1 x 10 8 m 3 of lava at an average ascent rate estimated at 13-20 md -1 (Nakada et al, 1995); the final spine extruded from late-1994 to early-1995 at a rate of approximately 0.8 md -1 (Yamashina et al, 1999). The rheology of the erupted dome lavas has been sourced of debate (Goto et al, 2020;Sato et al, 2021), as it is challenging to precisely reconstruct the physico-chemical, petrological and structural parameters which control rheology as a function of depth during eruption. For the late-stage spine, Nakada and Motomura (1999) proposed that it formed due to a lower effusion rate, which resulted in extensive magma degassing and crystallisation, and thus high viscosity, which promoted rupture and exogenic growth at relatively low strain rates (e.g., Hale and Wadge, 2008;Goto, 1999).…”

Section: -1995 Eruption Of Unzen Volcanomentioning

confidence: 99%

Transient conduit permeability controlled by a shift between compactant shear and dilatant rupture at Unzen volcano (Japan)

Lavallée

Miwa

Ashworth

et al. 2021

Preprint

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Abstract. The permeability of magma in shallow volcanic conduits controls the fluid flow and pore pressure development that regulates gas emissions and the style of volcanic eruptions. The architecture of the permeable porous structure is subject to changes as magma deforms and outgasses during ascent. Here, we present a high-resolution study of the permeability distribution across two conduit shear zones (marginal and central) developed in the dacitic spine that extruded towards the closing stages of the 1991–1995 eruption at Unzen volcano, Japan. The marginal shear zone is approximately 3.2 m wide and exhibits a 2-m wide, moderate shear zone with porosity and permeability similar to the conduit core, transitioning into a ~1-m wide, highly-sheared region with relatively low porosity and permeability, and an outer 20-cm wide cataclastic fault zone. The low porosity, highly-sheared rock further exhibits an anisotropic permeability network with slightly higher permeability along the shear plane (parallel to the conduit margin) and is locally overprinted by oblique dilational Riedel fractures. The central shear zone is defined by a 3-m long by ~9-cm wide fracture ending bluntly and bordered by a 15–40 cm wide damage zone with an increased permeability of ~3 orders of magnitude; directional permeability and resultant anisotropy could not be measured from this exposure. We interpret the permeability and porosity of the marginal shear zone to reflect the evolution of compactional (i.e., ductile) shear during ascent up to the point of rupture, estimated by Umakoshi et al. (2008), at ~500 m depth. At this point the compactional shear zone would have been locally overprinted by brittle rupture, promoting the development of a shear fault and dilational Riedel fractures during repeating phases of increased magma ascent rate, enhancing anisotropic permeability that channels fluid flow into, and along, the conduit margin. In contrast, we interpret the central shear zone as a shallow, late-stage dilational structure, which partially tore the spine core with slight displacement. We explore constraints from monitored seismicity and stick-slip behaviour to evaluate the rheological controls, which accompanied the upward shift from compactional toward dilational shear as magma approached the surface, and discuss their importance in controlling the permeability development of magma evolving from overall ductile to increasingly brittle behaviour during ascent and eruption.

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Section: -1995 Eruption Of Unzen Volcanomentioning

confidence: 99%

Transient conduit permeability controlled by a shift between compactant shear and dilatant rupture at Unzen volcano (Japan)

Lavallée

Miwa

Ashworth

et al. 2021

Preprint

View full text Add to dashboard Cite

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The centenary of IAVCEI 1919–2019 and beyond: origins and evolution of the International Association of Volcanology and Chemistry of the Earth’s Interior

Fernand

2022

Bull Volcanol

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IAVCEI originated in 1919 as one of the six inaugural “sections” of the International Union of Geodesy and Geophysics (IUGG). IUGG was formed by the International Research Council, which has now evolved to become the International Science Council (ISC). In 1933 the Section for Volcanology was renamed the International Association of Volcanology (IAV), and in 1967, it became the International Association of Volcanology and Geochemistry of the Earth’s Interior (IAVCEI). IAVCEI has been managed by 22 Presidents, 10 Secretaries-General, and their executive committees/bureaus. IAVCEI has always had a focus on facilitating the communication of volcanological research through organising a variety of international conferences, including IAVCEI General Assemblies, Scientific Assemblies, occasional Volcanological Congresses, and Cities on Volcanoes conferences. In addition, IAVCEI established research working groups initially which then became the association’s research commissions. The research commissions have also organised their own research workshops. Recently IAVCEI has also developed new groupings of researchers through their Network program, including the Early Career Researcher Network, which focus mostly on facilitating communication. Bulletin of Volcanology has been the official IAVCEI journal since 1924 and has undergone several facelifts in its cover and format. It has been very well served by its 11 volunteer editors, editorial board, and reviewers in almost 100 years of publication. In addition, IAVCEI was instrumental in instigating an inventory of known volcanoes through its Catalogue of the Volcanoes of the World series, a role now undertaken by the Smithsonian Institution. To acknowledge outstanding achievements in volcanological research, IAVCEI has established 6 awards since 1974. Developing a better understanding of how volcanoes erupt and the impacts of eruptions on society has been an integral responsibility of IAVCEI as the learned international association in volcanology. In the 1990s, IAVCEI initiated the Decade Volcanoes program to encourage research on 16 volcanoes that were deemed to pose significant risks to the communities around them. Some have erupted since then, but eruptions from other volcanoes have also provided significant insights into eruption processes and phenomena. Although IAVCEI’s future looks healthy, there are ways of being more proactive in improving services to members, including improving diversity and inclusiveness, greater gender balance for all positions on the IAVCEI Executive Committee, widening the representation of nationalities that serve on the Executive Committee, increasing membership numbers to generate greater income to support scientists in need of support to participate in IAVCEI activities, and significantly lowering the fee for open access publication of research papers in IAVCEI’s masthead journal, Bulletin of Volcanology . Supplementary Information The online version contains s...

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Reply to: Hiroaki Sato, Shigeru Suto, Tadahide Ui, Toshitsugu Fujii, Takahiro Yamamoto, Shinji Takarada, Keiichi Sakaguchi, “Flowage of the 1991 Unzen lava; discussion to Goto et al. ‘Rigid migration of Unzen lava rather than flow’, J. Volcanol. Geotherm. Res, 110, 107073.”

Goto

Fukui

Hiraga

et al. 2021

Journal of Volcanology and Geothermal Research

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Flowage of the 1991 Unzen lava; discussions to ‘Rigid migration of Unzen lava rather than flow’ J. Volcanol. Geotherm. Res., 110, 107073

Cited by 4 publications

References 27 publications

Transient conduit permeability controlled by a shift between compactant shear and dilatant rupture at Unzen volcano (Japan)

Transient conduit permeability controlled by a shift between compactant shear and dilatant rupture at Unzen volcano (Japan)

The centenary of IAVCEI 1919–2019 and beyond: origins and evolution of the International Association of Volcanology and Chemistry of the Earth’s Interior

Reply to: Hiroaki Sato, Shigeru Suto, Tadahide Ui, Toshitsugu Fujii, Takahiro Yamamoto, Shinji Takarada, Keiichi Sakaguchi, “Flowage of the 1991 Unzen lava; discussion to Goto et al. ‘Rigid migration of Unzen lava rather than flow’, J. Volcanol. Geotherm. Res, 110, 107073.”

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