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Estimating rates of decompression from textures of erupted ash particles produced by 1999-2006 eruptions of Tungurahua Volcano, Ecuador

Heather M. N. Wright, Katharine V. Cashman, Patricia A. Mothes, Minard L. Hall, Andres Gorki Ruiz and Jean-Luc Le Pennec
Estimating rates of decompression from textures of erupted ash particles produced by 1999-2006 eruptions of Tungurahua Volcano, Ecuador
Geology (Boulder) (May 2012) 40 (7): 619-622

Abstract

Persistent low- to moderate-level eruptive activity of andesitic volcanoes is difficult to monitor because small changes in magma supply rates may cause abrupt transitions in eruptive style. As direct measurement of magma supply is not possible, robust techniques for indirect measurements must be developed. Here we demonstrate that crystal textures of ash particles from 1999 to 2006 Vulcanian and Strombolian eruptions of Tungurahua volcano, Ecuador, provide quantitative information about the dynamics of magma ascent and eruption that is difficult to obtain from other monitoring approaches. We show that the crystallinity of erupted ash particles is controlled by the magma supply rate (MSR); ash erupted during periods of high magma supply is substantially less crystalline than during periods of low magma supply. This correlation is most easily explained by efficient degassing at very low pressures (<<50 MPa) and degassing-driven crystallization controlled by the time available prior to eruption. Our data also suggest that the observed transition from intermittent Vulcanian explosions at low MSR to more continuous periods of Strombolian eruptions and lava fountains at high MSR can be explained by the rise of bubbles through (Strombolian) or trapping of bubbles beneath (Vulcanian) vent-capping, variably viscous (and crystalline) magma.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 40
Serial Issue: 7
Title: Estimating rates of decompression from textures of erupted ash particles produced by 1999-2006 eruptions of Tungurahua Volcano, Ecuador
Affiliation: U. S. Geological Survey, Menlo Park, CA, United States
Pages: 619-622
Published: 20120523
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 32
Accession Number: 2012-065476
Categories: Quaternary geologyIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2012181; accessed on June 7, 2012
Illustration Description: illus. incl. sketch map
Source Medium: WWW
S01°28'01" - S01°28'01", W78°26'30" - W78°26'30"
Secondary Affiliation: University of Oregon, USA, United StatesEscuela Politecnica Nacional, ECU, EcuadorInstitut de Recherche pour le Developpement, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201234
Program Name: USGSOPNon-USGS publications with USGS authors
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