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Multivariate Analysis of Volcanic Particle Morphology: Methodology and Application of a Quantitative System of Fragmentation Mechanism Classification

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Multivariate Analysis of Volcanic Particle Morphology: Methodology and Application of a Quantitative System of Fragmentation Mechanism Classification MULTIVARIATE ANALYSIS OF VOLCANIC PARTICLE MORPHOLOGY: METHODOLOGY AND APPLICATION OF A QUANTITATIVE SYSTEM OF FRAGMENTATION MECHANISM CLASSIFICATION Meredith Ryan Avery A Thesis Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May 2015 Committee: Kurt Panter, Advisor Charles Onasch Peter Gorsevski ii ABSTRACT Kurt Panter, Advisor Eruption mechanism plays a large part in the level of hazards a volcano can produce and can also have a tremendous effect on the climate when an eruption column reaches into the stratosphere. The purpose of this study is to refine and produce a methodology using Scanning Electron Microscopy (SEM) and image processing software to characterize ash particle morphology and use that to determine the fragmentation mechanism of any ash deposit. A quantitative method of determining ash morphology and linking it to eruptive styles can be applied to volcanic deposits worldwide and may be used to predict future hazards. The ash samples that are used in this study were collected from tephra deposits on Mount Erebus, Antarctica (< 15 ka), Mt. Redoubt, Alaska (2009), and Taupo, New Zealand (1.8 ka). The Taupo and Redoubt ash represent endmembers of phreatomagmatic and magmatically fragmented plinian eruptions, respectively. The fragmentation mechanism for the Mount Erebus ash is unknown but has been postulated to be a mixture of both phreatomagmatic and magmatic activity (surtseyan and strombolian, respectively). The ash was carefully hand-sieved to ~1mm diameter and imaged by SEM and then processed for morphological properties including rectangularity, circularity, compactness, elongation, solidity, etc. These morphological parameters were used in several statistical analysis to evaluate similarity and differences between deposits and to help constrain fragmentation mechanism. Discriminant analysis on all morphological parameters was found to be the best in separating the data and showing a linear trend between the two fragmentation mechanisms. The separation however, was only achieved after including parameters that are somewhat dependent iii on vesicle amount, size, and distribution on the particle surface. This analysis also gave further insight to the Erebus tephra which was formed by both mechanisms during a single eruptive pulse. Other separations based on eruption style can also be inferred from this analysis. Regions of wet and dry strombolian style eruptions dominate the right quadrants; whereas, the left quadrants are dominated by phreatomagmatic and magmatic plinian style eruptions. Future deposits could not only verify these regions, but also expand the classification to include other eruption styles (vulcanian and vesuvian). iv ACKNOWLEDGMENTS I would like to thank many of the people who supported this project. First, thank you to my advisor, Dr. Kurt Panter, for all his guidance and encouragement throughout this project. Without his inquisitive nature, this project would not have expanded and grown the way it ultimately has. Also, thank you to my committee members, Dr. Charles Onasch and Dr. Peter Gorsevski, for providing direction and assistance during the various stages of research. Furthermore, this project would have been impossible without the samples provided by Kristi Wallace at the USGS Alaska Volcano Observatory and Dr. Bruce Houghton at the University of Hawaii. Your communication and generosity was incredibly appreciated. I would also like to extend a thank you to Dr. Sharon Allen at the University of Tasmania and Dr. Pierfrancesco Dellino at Bari University for the donation of samples that can be used in a future follow-up study. A special thank you to the Old Dominion University Biology Department for the use of the LEO 435VP Scanning Electron Microscope during the summer of 2014. To the University of Toledo Center for Materials and Sensor Characterization (CMSC), in particular Dr. Joseph Lawrence, thank you for the training and use of the Hitachi S4800 II Scanning Electron Microscope. Many thanks to Dr. Chris Haley and Dr. Victor Townsend at Virginia Wesleyan College for their encouragement and preliminary sample work completed on the Hitachi S- 3400N VP II Scanning Electron Microscope. Also, I would like to thank the BGSU Geology Department as a whole for accepting me into the program and giving me a chance to learn from some of the brightest scientists in the world. Finally, I would like to thank all the special people in my life for all they have done to get me to this point with their constant love and support. I want to especially thank my mother and hero Christine Avery, who does so much and deserves so much more. I want to also thank my v father Robert J. Avery, my grandmother Jacqueline Singletary, and my cousins Berry and Danielle Cobb for all the guidance and love you’ve given me over the years. To my grandfather, Jim Singletary, I wish you could see what I’ve become, but I know you’d be proud. Also to my fiancé, Javier Vega Jr., thank you for supporting me and patiently waiting for me to finish graduate school. Without all of you, I would not have been able to achieve all my goals. Thank you all so much! vi TABLE OF CONTENTS Page INTRODUCTION ................................................................................................................. 1 BACKGROUND ............................................................................................................ 5 Mechanisms for the Formation of Ash ...................................................................... 5 Tephra Units Studied ................................................................................................. 7 Taupo – 1.8 ka, Hatepe Ash unit 3 subunit D (HA3-D) ................................ 8 Redoubt – 2009, fall deposit AT-1617 & 1876 ............................................. 9 Erebus - < 15 ka, fall deposit SC4 (BW03-015) ............................................ 10 METHODOLOGY ............................................................................................................ 12 SEM Analysis ............................................................................................................ 13 Image Analysis........................................................................................................... 14 RESULTS ............................................................................................................ 19 K-means Cluster Analysis .......................................................................................... 19 Box Plot Comparison ................................................................................................. 19 Histograms with Density Curves for RCCE Parameters ........................................... 20 T-Testing on All Parameters ...................................................................................... 20 Discriminant Function Analysis ................................................................................ 21 Grain Size Effect ........................................................................................................ 23 Proximal vs Distal Effect ........................................................................................... 25 Comparison to Other Deposits ................................................................................... 26 Stromboli, Italy – Lautze et al. (2013) ........................................................... 26 Erebus, Antarctica, englacial ash – Iverson et al. (2014) ............................... 26 vii Lipari, Monte Pilato-Rocche Rosse deposit, Italy – Dellino and La Volpe (1996) .............................................................. 27 DISCUSSION ............................................................................................................ 29 Comparison of Similar Studies ...................................................................... 30 Size Bias on Particle Outline Sensitive Parameters ....................................... 31 Tephra-fall Deposits and Abrasion ................................................................ 31 Deposit comparison by Factor Analysis ........................................................ 33 Fragmentation Mechanism Classification by Discriminant Analysis ............ 35 Morphological trend reveals eruption style ....................................... 35 The eruption style for the Erebus SC4 deposit .................................. 37 CONCLUSIONS ............................................................................................................ 39 REFERENCES ............................................................................................................ 41 TABLES ................................................................................................................................ 47 FIGURES ............................................................................................................................... 55 APPENDIX A ........................................................................................................................ 83 APPENDIX B ........................................................................................................................ 137 viii LIST OF TABLES Table Page 1 Volcanic eruption type characteristics ....................................................................... 47 2 K-means 2 cluster analysis by volcano .....................................................................
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