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Particle sizes of andesitic ash fallout from vertical eruptions and co-pyroclastic flow clouds, Volcan de Colima, Mexico

Jason R. Evans, Jacqueline E. Huntoon, William I. Rose, Nick R. Varley and John A. Stevenson
Particle sizes of andesitic ash fallout from vertical eruptions and co-pyroclastic flow clouds, Volcan de Colima, Mexico
Geology (Boulder) (October 2009) 37 (10): 935-938

Abstract

We report particle-size distributions for andesitic ash fall from vertical eruptions and clouds above block-and-ash flows at Volcan de Colima, Mexico, during 2004-2006. We analyzed 17 samples using laser diffraction: 11 from vertical eruptions and 6 from block-and-ash flows (co-pyroclastic flow ash). Vertical eruptions produce well-sorted fall deposits, whereas co-pyroclastic fall deposits are poorly sorted, with high proportions of very fine grained ash (<30 mu m). Statistical analysis shows particle-size distributions of vertical eruptions are more leptokurtic (peaked) than co-pyroclastic samples. Deconvolution of grain-size histograms shows that co-pyroclastic samples have at least one subpopulation with a mode of 8.3-8.7 phi (2.4-3.1 mu m). Estimates of the number of particles in different size ranges show that co-pyroclastic samples contain much greater numbers of very fine particles than vertical eruption samples. Our results provide no direct evidence that milling or comminution produces hazardous fine ash particles in pyroclastic flows, but are consistent with that interpretation.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 37
Serial Issue: 10
Title: Particle sizes of andesitic ash fallout from vertical eruptions and co-pyroclastic flow clouds, Volcan de Colima, Mexico
Affiliation: Michigan Technological University, Houghton, MI, United States
Pages: 935-938
Published: 200910
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 35
Accession Number: 2009-098003
Categories: Quaternary geologyIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. charts, 2 tables
N19°31'00" - N19°31'00", W103°37'60" - W103°37'60"
Secondary Affiliation: Universidad de Colima, MEX, MexicoUniversity of Manchester, GBR, United Kingdom
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: 200952
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