Rapid and slow: Varying magma ascent rates as a mechanism for Vulcanian explosions

Mike Cassidy; Paul D. Cole; Kelby E. Hicks; Nick R. Varley; Nial Peters; Allan H. Lerner

doi:10.1016/j.epsl.2015.03.025

Rapid and slow: Varying magma ascent rates as a mechanism for Vulcanian explosions

Mike Cassidy^*, Paul D. Cole, Kelby E. Hicks, Nick R. Varley, Nial Peters, Allan H. Lerner

^*Corresponding author for this work

Geography, Earth and Environmental Sciences

Research output: Contribution to journal › Article › peer-review

49 Citations (Scopus)

Abstract

Vulcanian explosions are one of the most common types of volcanic activity observed at silicic volcanoes. Magma ascent rates are often invoked as being the fundamental control on their explosivity, yet this factor is poorly constrained for low magnitude end-member Vulcanian explosions, which are particularly poorly understood, partly due to the rarity of ash samples and low gas fluxes. We describe ash generated by small Vulcanian explosions at Volcán de Colima in 2013, where we document for the first time marked differences in the vesicularity, crystal characteristics (volume fraction, size and shape) and glass compositions in juvenile material from discrete events. We interpret these variations as representing differing ascent styles and speeds of magma pulses within the conduit. Heterogeneous degassing during ascent leads to fast ascending, gas-rich magma pulses together with slow ascending gas-poor magma pulses within the same conduit. This inferred heterogeneity is complemented by SO₂ flux data, which show transient episodes of both open and closed system degassing, indicating efficient shallow fracture sealing mechanisms, which allows for gas overpressure to generate small Vulcanian explosions.

Original language	English
Pages (from-to)	73-84
Number of pages	12
Journal	Earth and Planetary Science Letters
Volume	420
DOIs	https://doi.org/10.1016/j.epsl.2015.03.025
Publication status	Published - 5 Jun 2015

Bibliographical note

Funding Information:
We wish to thank Patricia Nadeau for her Matlab code, Arjan Dijkstra, Jodie Fisher, Glenn Harper and Richard Hartley at Plymouth University for lab assistance. Jonathan Barry, Steffano Vissani and other CIIV volunteers for field assistance. Kayla Iacovino and Yves Moussallam at the University of Cambridge for development of the DOAS code. Stuart Kearns for assistance with EPMA analysis at the University of Bristol. Discussions with Katie Preece, Arjan Dijkstra, Tamsin Mather and David Pyle helped to progress the ideas in this manuscript. The constructive comments of two anonymous reviewers and from editor Tim Elliott considerably improved this manuscript. This research was supported by a NERC urgency grant ( NE/L000741/1 ).

Publisher Copyright:
© 2015.

Keywords

Conduit dynamics
Degassing
Effusive-explosive
Microlites
SO
Volcán de Colima

ASJC Scopus subject areas

Geophysics
Geochemistry and Petrology
Earth and Planetary Sciences (miscellaneous)
Space and Planetary Science

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10.1016/j.epsl.2015.03.025

Cite this

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title = "Rapid and slow: Varying magma ascent rates as a mechanism for Vulcanian explosions",

abstract = "Vulcanian explosions are one of the most common types of volcanic activity observed at silicic volcanoes. Magma ascent rates are often invoked as being the fundamental control on their explosivity, yet this factor is poorly constrained for low magnitude end-member Vulcanian explosions, which are particularly poorly understood, partly due to the rarity of ash samples and low gas fluxes. We describe ash generated by small Vulcanian explosions at Volc{\'a}n de Colima in 2013, where we document for the first time marked differences in the vesicularity, crystal characteristics (volume fraction, size and shape) and glass compositions in juvenile material from discrete events. We interpret these variations as representing differing ascent styles and speeds of magma pulses within the conduit. Heterogeneous degassing during ascent leads to fast ascending, gas-rich magma pulses together with slow ascending gas-poor magma pulses within the same conduit. This inferred heterogeneity is complemented by SO2 flux data, which show transient episodes of both open and closed system degassing, indicating efficient shallow fracture sealing mechanisms, which allows for gas overpressure to generate small Vulcanian explosions.",

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author = "Mike Cassidy and Cole, {Paul D.} and Hicks, {Kelby E.} and Varley, {Nick R.} and Nial Peters and Lerner, {Allan H.}",

note = "Funding Information: We wish to thank Patricia Nadeau for her Matlab code, Arjan Dijkstra, Jodie Fisher, Glenn Harper and Richard Hartley at Plymouth University for lab assistance. Jonathan Barry, Steffano Vissani and other CIIV volunteers for field assistance. Kayla Iacovino and Yves Moussallam at the University of Cambridge for development of the DOAS code. Stuart Kearns for assistance with EPMA analysis at the University of Bristol. Discussions with Katie Preece, Arjan Dijkstra, Tamsin Mather and David Pyle helped to progress the ideas in this manuscript. The constructive comments of two anonymous reviewers and from editor Tim Elliott considerably improved this manuscript. This research was supported by a NERC urgency grant ( NE/L000741/1 ). Publisher Copyright: {\textcopyright} 2015.",

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AU - Cole, Paul D.

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AU - Varley, Nick R.

AU - Peters, Nial

AU - Lerner, Allan H.

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N2 - Vulcanian explosions are one of the most common types of volcanic activity observed at silicic volcanoes. Magma ascent rates are often invoked as being the fundamental control on their explosivity, yet this factor is poorly constrained for low magnitude end-member Vulcanian explosions, which are particularly poorly understood, partly due to the rarity of ash samples and low gas fluxes. We describe ash generated by small Vulcanian explosions at Volcán de Colima in 2013, where we document for the first time marked differences in the vesicularity, crystal characteristics (volume fraction, size and shape) and glass compositions in juvenile material from discrete events. We interpret these variations as representing differing ascent styles and speeds of magma pulses within the conduit. Heterogeneous degassing during ascent leads to fast ascending, gas-rich magma pulses together with slow ascending gas-poor magma pulses within the same conduit. This inferred heterogeneity is complemented by SO2 flux data, which show transient episodes of both open and closed system degassing, indicating efficient shallow fracture sealing mechanisms, which allows for gas overpressure to generate small Vulcanian explosions.

AB - Vulcanian explosions are one of the most common types of volcanic activity observed at silicic volcanoes. Magma ascent rates are often invoked as being the fundamental control on their explosivity, yet this factor is poorly constrained for low magnitude end-member Vulcanian explosions, which are particularly poorly understood, partly due to the rarity of ash samples and low gas fluxes. We describe ash generated by small Vulcanian explosions at Volcán de Colima in 2013, where we document for the first time marked differences in the vesicularity, crystal characteristics (volume fraction, size and shape) and glass compositions in juvenile material from discrete events. We interpret these variations as representing differing ascent styles and speeds of magma pulses within the conduit. Heterogeneous degassing during ascent leads to fast ascending, gas-rich magma pulses together with slow ascending gas-poor magma pulses within the same conduit. This inferred heterogeneity is complemented by SO2 flux data, which show transient episodes of both open and closed system degassing, indicating efficient shallow fracture sealing mechanisms, which allows for gas overpressure to generate small Vulcanian explosions.

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Rapid and slow: Varying magma ascent rates as a mechanism for Vulcanian explosions

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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