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Hydrothermal alteration can result in pore pressurization and volcano instability

Michael J. Heap, Tobias Baumann, H. Albert Gilg, Stephan Kolzenburg, Amy G. Ryan, Marlene Villeneuve, J. Kelly Russell, Lori A. Kennedy, Marina Rosas-Carbajal and Michael A. Clynne
Hydrothermal alteration can result in pore pressurization and volcano instability
Geology (Boulder) (July 2021) 49 (11): 1348-1352


The collapse of a volcanic flank can be destructive and deadly. Hydrothermal alteration is common to volcanoes worldwide and is thought to promote volcano instability by decreasing rock strength. However, some laboratory studies have shown that not all alteration reduces rock strength. Our new laboratory data for altered rhyodacites from Chaos Crags (Lassen volcanic center, California, USA) show that pore- and crack-filling mineral precipitation can reduce porosity and permeability and increase strength, Young's modulus, and cohesion. A significant reduction in permeability, by as much as four orders of magnitude, will inhibit fluid circulation and create zones of high pore fluid pressure. We explored the consequences of pore fluid pressurization on volcano stability using large-scale numerical modeling. Upscaled physical and mechanical properties for hydrothermally altered rocks were used as input parameters in our modeling. Results show that a high-pore-pressure zone within a volcano increases volcano deformation and that increasing the size of this zone increases the observed deformation. Hydrothermal alteration associated with mineral precipitation, and increases to rock strength, can therefore promote pore pressurization and volcano deformation, increasing the likelihood of volcano spreading, flank collapses, and phreatic/phreatomagmatic explosions. We conclude that porosity-decreasing alteration, explored here, and porosity-increasing alteration can both promote volcano instability and collapse, but by different mechanisms. Hydrothermal alteration should therefore be monitored at volcanoes worldwide and incorporated into hazard assessments.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 49
Serial Issue: 11
Title: Hydrothermal alteration can result in pore pressurization and volcano instability
Affiliation: Universite de Strasbourg, Institut Terre et Environnement de Strasbourg, Strasbourg, France
Pages: 1348-1352
Published: 20210720
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 30
Accession Number: 2021-053197
Categories: Igneous and metamorphic petrologyGeomorphology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch map
N40°31'00" - N40°31'00", W121°31'00" - W121°31'00"
Secondary Affiliation: Johannes Gutenberg University Mainz, Mainz, DEU, GermanyTechnical University of Munich, Munich, DEU, GermanyState University of New York at Buffalo, Buffalo, NY, USA, United StatesUniversity of Minnesota-Twin Cities, Minneapolis, MN, USA, United StatesMontanuniversitaet Leoben, Leoben, AUT, AustriaUniversity of British Columbia, Vancouver, BC, CAN, CanadaUniversite de Paris, Paris, FRA, FranceU. S. Geological Survey, Menlo Park, CA, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, 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: 202137
Program Name: USGSOPNon-USGS publications with USGS authors
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