EXPLOSIVE SUBAQUEOUS ERUPTIONS: THE INFLUENCE OF VOLCANIC JETS ON ERUPTION DYNAMICS AND TEPHRA DISPERSAL IN UNDERWATER ERUPTIONS by RYAN CAIN CAHALAN A DISSERTATION Presented to the Department of Earth ScIences and the Graduate School of the UniversIty of Oregon In partIaL fulfiLLment of the requirements for the degree of Doctor of PhiLosophy December 2020 DISSERTATION APPROVAL PAGE Student: Ryan CaIn CahaLan Title: ExplosIve Subaqueous EruptIons: The Influence of Volcanic Jets on EruptIon DynamIcs and Tephra DIspersaL In Underwater EruptIons This dissertatIon has been accepted and approved in partIaL fulfiLLment of the requirements for the Doctor of PhiLosophy degree in the Department of Earth ScIences by: Dr. Josef Dufek ChaIrperson Dr. Thomas GIachettI Core Member Dr. Paul WaLLace Core Member Dr. KeLLy Sutherland InstItutIonaL RepresentatIve and Kate Mondloch Interim VIce Provost and Dean of the Graduate School OriginaL approvaL sIgnatures are on fiLe wIth the UniversIty of Oregon Graduate School. Degree awarded December 2020 II © 2020 Ryan Cain Cahalan III DISSERTATION ABSTRACT Ryan CaIn CahaLan Doctor of PhiLosophy Department of Earth ScIences December 2020 Title: ExplosIve Subaqueous EruptIons: The Influence of Volcanic Jets on EruptIon DynamIcs and Tephra DIspersaL In Underwater EruptIons Subaqueous eruptIons are often overlooked in hazard consIderatIons though they represent sIgnificant hazards to shipping, coastLInes, and in some cases, aIrcraft. In explosIve subaqueous eruptIons, volcanic jets transport fragmented tephra and exsolved gases from the conduit into the water column. Upon eruptIon the volcanic jet mIxes wIth seawater and rapidly cools. This mIxing and assocIated heat transfer ultImateLy determInes whether steam present in the jet wILL completeLy condense or rise to breach the sea surface and become a subaeriaL hazard. We deveLop a multIphase modeL wIth sub-grid caLculatIons for in situ steam condensatIon to explore the reLatIonshIp between eruptIon conditIons (e.g. water depth, mass flux, eruptIon temperature) and the produced steam jet heIght and breach potentIaL. We find that mass flux is the predomInant control of jet heIght, more so than aspects of vent geometry. After investIgatIon of the controls of jet dynamIcs, we determIne how jet dynamIcs affect mass transport and partItIoning in the water column. ULtImateLy, this is the princIple concern in studying eruptIons, to determIne when, where, why, and how tephra Is deposIted. We utILIze the multIphase subaqueous eruptIon modeL to take the fundamentaL step in this investIgatIon, to identIfy transport mechanisms that lead to iv different mass partItIoning outcomes. The results of this investIgatIon show trends in mass partItIoning assocIated wIth varying eruptIon parameters (eruptIon temperature and vent veLocIty) and partIcLe parameters (sIze, densIty, concentratIon). We compare mass partItIoning results for eruptIons wIth and wIthout gas jets to define features specIfic to explosIve eruptIons. FInaLLy, we aggregate the modeL results and observatIons into eruptIon column transport regimes. This work represents the first look at many of these dynamIc processes. v CURRICULUM VITAE NAME OF AUTHOR: Ryan CaIn CahaLan GRADUATE AND UNDERGRADUATE SCHOOLS ATTENDED: UniversIty of Oregon, Eugene Georgia InstItute of Technology, AtLanta, Georgia UniversIty of Texas, AustIn, Texas DEGREES AWARDED: Doctor of PhiLosophy, Earth ScIences, 2020, UniversIty of Oregon BacheLor of ScIence, Geology, 2012, UniversIty of Texas AREAS OF SPECIAL INTEREST: Volcanology and Submarine Volcanology ComputatIonaL ModeLIng PROFESSIONAL EXPERIENCE: Research AssIstant, Jackson School of GeoscIences, UniversIty of Texas, AustIn, 2010-2013 Teaching AssIstant, Earth and Atmospheric ScIences, Georgia InstItute of Technology, AtLanta, 2014 Teaching AssIstant, Department of Earth ScIences, UniversIty of Oregon, Eugene, 2018-2019 MESH research cruise to Havre Seamount, Kermadec Arc, NZ Co-PI: Dr. Bruce Houghton, U. HawaII; Dr. Rebecca Carey, UTAS, 2015 GRANTS, AWARDS, AND HONORS: Graduate Research FeLLowship, “Experimentation and numerical modeling of explosive subaqueous eruption dynamics”, NatIonaL ScIence FoundatIon, 2015 vi Graduate Student of the Month, School of Earth and Atmospheric ScIences, Georgia Tech, 2014 Outstanding Student Paper Award, “Coupled diffusion of lithium and yttrium (+HREE) in garnet”, American GeophysIcaL Union, 2012 Undergraduate Research FeLLowship, “Determination of lithium diffusion rates in garnet and coupled diffusion of lithium and yttrium in garnet”, UniversIty of Texas at AustIn, 2011 PUBLICATIONS: CahaLan, R. C. & Dufek, J. (In Review) Condensable gas jets in submarine eruptions: A multiphase model for hydrous phase change in explosive eruptions underwater. JournaL of GeophysIcaL Research. M. Manga, K. E. Fauria, C. LIn, S. J. MItcheLL, M. Jones, C. Conway, W. Degruyter, B. HosseIni, R. Carey, R. CahaLan, B.F. Houghton, J.D.L. White, M. JutzeLer, S. A. Soule, and K. Tani (2018) The pumice raft-forming 2012 Havre submarine eruption was effusive. Earth and PLanetary ScIence Letters. v. 489, p. 49-58. https://doi.org/10.1016/j.epsL.2018.02.025 R. Carey, S.A. Soule, M. Manga, J.D.L. White, J. McPhie, R. Wysoczanski, M. JutzeLer, K. Tani, D. Yoerger, D. Fornari, F. Caratori-TontIni, B. Houghton, S. MItcheLL, F. IkegamI, C. Conway, A. Murch, K. Fauria, M. Jones, R. CahaLan, and W. McKenzIe (2018). The largest deep-ocean silicic volcanic eruption of the past century. ScIence Advances v. 4 no. 1e1701121. doi: 10.1126/scIadv.1701121 R.C. CahaLan, E.D. KeLLy, and W.D. Carlson (2014). Rates of Li diffusion in garnet: Coupled transport of Li and Y+REEs. American MIneraLogist v. 99 no. 8-9 p.1676-1682. doi: 10.2138/am.2014.4676 vii ACKNOWLEDGMENTS I would lIke to express my deepest gratItude to the various individuaLs whom have supported me throughout my graduate school experience. FIrst, I would lIke to thank my advisor, Dr. Josef Dufek, for his mentorship and guidance, and most of aLL, for his unending optImIsm that has reInvigorated my drive at tImes where I feLt entIreLy spent. I thank my dissertatIon commIttee members, Dr. KeLLy Sutherland, Dr. Paul WaLLace, and Dr. Thomas GIachettI, for theIr counseL that has heLped steer my research, theIr encouraging words, and theIr tIme in reading and editIng this document. I would aLso lIke to thank Dr. Rebecca Carey and the MESH research crew who invited me to partIcIpate In the research cruise to the Havre Seamount, which has been one of the most formatIve experiences in my graduate studies. My sIncerest thanks to Dave and Fred for theIr contInuing friendship, for the drafts they have read, and the late nights and chats that kept grad school fun and interestIng. AdditIonaLLy, I wouLd lIke to thank my famILy, Sean, Hunter, Mom, and Dad, for the endless support and love. To my parents, who gave me my curious nature and the freedom to pursue it. And to my brothers, who have encouraged me and been a deep weLL of creatIve inspiratIon and strength. To my dear friends Jani, Cameron, Matt, Luju, Jacob, and Eric, who have provided great debate, conversatIon, laughter, and inspiratIon that spans multIple decades and wILL hopefulLy contInue for many more. Thank you to you aLL. LastLy, to my beautIful and supportIve wIfe, who has uprooted her lIfe twIce now and sacrificed much to aLLow me to pursue my career. WIthout you, there is lIttLe chance that I finish this degree and contInue on. You are everything. I love you. Thank you. viii I wIsh to express apprecIatIon to The UniversIty of Texas, Georgia InstItute of Technology, and The UniversIty of Oregon for financIaL support and opportunitIes which have aLLowed me to grow and freeLy conduct my research. Hook’em Horns! I would aLso LIke to thank the NatIonaL ScIence FoundatIon Graduate Research FeLLowship Program, which has funded me for a large portIon of my graduate schoolIng and has provided me, and many others, wIth the academIc freedom to explore interestIng and new ideas. ix TABLE OF CONTENTS Chapter Page I. INTRODUCTION .................................................................................................... 1 IntroductIon to Subaqueous EruptIons ................................................................... 1 The Anatomy of an ExplosIve Subaqueous EruptIon ............................................ 4 FragmentatIon .................................................................................................. 5 EruptIon Jet ...................................................................................................... 8 HydrothermaL PLume ........................................................................................ 12 Tephra DIspersaL .............................................................................................. 13 Overview of Subaqueous EruptIon ModeLs ........................................................... 13 MultIphase ModeLs ................................................................................................. 15 ObjectIves .............................................................................................................. 16 II. EXPLOSIVE SUBMARINE ERUPTIONS: THE ROLE OF CONDENSABLE GAS JETS IN UNDERWATER VOLCANISM...................... 19 IntroductIon ............................................................................................................ 19 ObservatIons and Evidence of Submarine EruptIon Jets ................................. 20 Steam CondensatIon in EruptIons ...................................................................