Plinian eruptions are commonly fed by intermediate to silicic magmas and originate both from single central vent and from km-long eruptive fissures defined by alignments of several vents. In the latter case, multiple vents can be active at the same time or sequentially, producing a complex stratigraphy of proximal deposits in which relations between the vent(s) source and tephra beds in medial area are difficult to establish. In addition, changes in the eruptive style may occur, overlapping or following the main sustained Plinian phase, making the reconstruction of eruptions behavior over time hard to constrain. Detailed field studies of tephra deposits, together with sedimentological and textural characterization of the erupted materials can provide wide datasets to understand complex eruptive sequences often associated with linear-source Plinian eruptions. In this context we investigate the stratigraphy of the AD 1914 Taisho eruption, the most recent Plinian eruptive episode of Sakurajima Volcano (Japan). The reconstruction of the Taisho eruption, based on the chronicles and the re-interpretation of the tephra deposits, depicts an eruptive scenario in which the eruption began with a Plinian explosive phase characterized by the rise of two convective columns simultaneously from two parallel, newly-opened, fissures located on two opposite sides of the volcano. After 36-48 hours, the eruption evolved toward an effusive activity with the outpouring of andesitic lava flows for several months, accompanied by ash emissions and minor discrete Vulcanian explosions. This field-based methodology can be extend to more silicic and larger volume eruptions, as for example the ~ AD 1315 Kaharoa eruption, the youngest rhyolitic Plinian eruption of the Tarawera Volcanic Complex (New Zealand). The eruption developed from multiple vents along an 8 km linear zone and exhibited a complex succession of different eruptive styles, intensities, and dynamics over an estimated ~ 5-year period of time, including initial phreatomagmatic and Plinian explosions with associated pyroclastic density currents, extrusions of lava domes and block and ash flows. The field-based approach is an essential and rapid tool to understand the complex evolution of volcanic eruptions in various time-scales, to establish eruptive scenarios and to define potential volcanic risk associated to the large spectrum of eruptive styles presented by these eruptions.

Understanding complex evolution of intermediate to silicic linear-source Plinian eruptions: Sakurajima volcano (Japan) and Tarawera Volcanic Complex (New Zealand) as case studies / Todde, A.; Cioni, R.; Nemeth, K.; Pistolesi, M.; Geshi, N.; Bonadonna, C.; Biass, S.. - ELETTRONICO. - (2017), pp. 1-1. (Intervento presentato al convegno IAVCEI General Assembly tenutosi a Portland (USA)).

Understanding complex evolution of intermediate to silicic linear-source Plinian eruptions: Sakurajima volcano (Japan) and Tarawera Volcanic Complex (New Zealand) as case studies

CIONI, RAFFAELLO;PISTOLESI, MARCO;
2017

Abstract

Plinian eruptions are commonly fed by intermediate to silicic magmas and originate both from single central vent and from km-long eruptive fissures defined by alignments of several vents. In the latter case, multiple vents can be active at the same time or sequentially, producing a complex stratigraphy of proximal deposits in which relations between the vent(s) source and tephra beds in medial area are difficult to establish. In addition, changes in the eruptive style may occur, overlapping or following the main sustained Plinian phase, making the reconstruction of eruptions behavior over time hard to constrain. Detailed field studies of tephra deposits, together with sedimentological and textural characterization of the erupted materials can provide wide datasets to understand complex eruptive sequences often associated with linear-source Plinian eruptions. In this context we investigate the stratigraphy of the AD 1914 Taisho eruption, the most recent Plinian eruptive episode of Sakurajima Volcano (Japan). The reconstruction of the Taisho eruption, based on the chronicles and the re-interpretation of the tephra deposits, depicts an eruptive scenario in which the eruption began with a Plinian explosive phase characterized by the rise of two convective columns simultaneously from two parallel, newly-opened, fissures located on two opposite sides of the volcano. After 36-48 hours, the eruption evolved toward an effusive activity with the outpouring of andesitic lava flows for several months, accompanied by ash emissions and minor discrete Vulcanian explosions. This field-based methodology can be extend to more silicic and larger volume eruptions, as for example the ~ AD 1315 Kaharoa eruption, the youngest rhyolitic Plinian eruption of the Tarawera Volcanic Complex (New Zealand). The eruption developed from multiple vents along an 8 km linear zone and exhibited a complex succession of different eruptive styles, intensities, and dynamics over an estimated ~ 5-year period of time, including initial phreatomagmatic and Plinian explosions with associated pyroclastic density currents, extrusions of lava domes and block and ash flows. The field-based approach is an essential and rapid tool to understand the complex evolution of volcanic eruptions in various time-scales, to establish eruptive scenarios and to define potential volcanic risk associated to the large spectrum of eruptive styles presented by these eruptions.
2017
IAVCEI
IAVCEI General Assembly
Portland (USA)
Todde, A.; Cioni, R.; Nemeth, K.; Pistolesi, M.; Geshi, N.; Bonadonna, C.; Biass, S.
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/1094322
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