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V·M·I University Microfilms International a Bell & Howell Information Company 300 North Zeeb Road INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adverselyaffect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyrightmaterial had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand corner and continuing from left to right in equal sectionswith small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. V·M·I University Microfilms International A Bell & Howell Information Company 300 North Zeeb Road. Ann Arbor. M148106-1346 USA 313/761-4700 800:521·0600 Order Number 9312207 The application of remotely sensed data to studies of volcanism within the Galapagos Islands Munro, Duncan Crawford, Ph.D. University of Hawaii, 1992 Copyright @1992 by Munro, Duncan Crawford. All rights reserved. V·M·I 300 N. ZeebRd. Ann Arbor,MI 48106 TIlE APPLICATION OF REMOTELY SENSED DATA TO STUDIES OF VOLCANISM WITHIN TIlE GALAPAGOS ISLANDS A DISSERTATION SUBMITI'ED TO TIlE GRADUATE DIVISION OF TIlE UNIVERSITY OF HAWAIl IN PARTIAL FULFILLMENT OF TIlE REQUIREMENTS FOR THE DEGREE OF DOCfOR OF PHILOSOPHY IN GEOLOGY AND GEOPHYSICS DECEMBER 1992 By Duncan Crawford Munro Dissertation Committee Peter J. Mouginis-Mark, Chairperson George P. L. Walker Lionel Wilson Matthew McGranaghan Brian Popp iii ©Copyright1992 by Duncan Crawford Munro iv ACKNOWLEDGEMENTS To state that this dissertation is "by" Duncan C. Munro diminishes the efforts of many colleagues, freinds and family who have helped in its production. To thank them all would take many volumes and it must suffice here to acknowledge those who have contributed above and beyond the normal call of duty. Firstly (I know he hates that word!), the DSM (Distinguished Service Medal) goes to the long suffering Dr. Peter Mouginis-Mark for letting me loose on the topic of volcanism in the Galapagos Islands, working to ensure that funding for the research was available, and for tolerating my sense of humor or, as some would have it, that which I have in place of a sense of humor! Secondly, I thank Dr. Scott Rowland for his constant level of effort and enthusiasm for field work and manuscript preparation. Were it not for graduate division rules he would be the sixth commitee member and receive more of the recognition he deserves. Additionally, all those who served on my commitee deserve a special mention. Dr. George Walker for continually finding new papers ofrelevance to the topic, the late Dr. William Coulbourn who taught the best class I have ever taken, Dr. Brian Popp for efforts under pressure, Dr. Matthew McGranaghan for dedication to outside commitee member duties, Dr. Lionel Wilson ("Bluebeard" to you pal!), and the cavalry in the form of Dr. Peter Francis who appeared over the ridge just as the whole thing was looking desperate! Dr. Paul Lucey and Tim Williams provided the technical expertise and know-how for the construction of the field radiometer used in this study and get special thanks for their time and efforts, and their ability to finish projects on time. I am also extremely grateful that they did not reveal to me thay had left out a screw in the filter wheel mechanism (hey, ifit ain't broke don't fix it, right?) Dr. Pam Blake helped to unravel the workings of LOWTRAN atmospheric models and rescued me up from the depths of the GARP software package. The final award for technical assistance goes to Harold Garbeil v for seeing life as it really is and fixing all the glitches in LAS and various other software packages too numerous to mention. It is difficult not to lapse into some horribly gushing tribute to one's family and friends at such times as completion of a doctorate, but on the other hand the odd gushing tribute never hurt, so here goes! To my wife Sharon, I extend heartfelt thanks for her tolerance ofbehavior more fitting to a 3 than a 33 year old and for all her support through the years. Words cannot express the depth of gratitude which is her due. To Ted and Barbara Rodgers for constant kindness and making me welcome in their home, to my own parents for their tolerance and patience and to my extended family, lowe a huge debt for their contributions to this work. My fellow graduate students have all helped in one way or another to cajole and bully me to the final hurdle, but to Mike Knight and Peter Sedwick I raise a glass of the cheapest beer I could find to toast their efforts on my behalf. Thank you one and all. vi ABSTRACT This dissertation presents the results of three research projects that examine eruption source vents and their products in order to interpret the structure and internal dynamics ofthe seven major shield volcanoes that comprise Islas Isabela and Fernandina, the two westernmost Galapagos Islands. Difficult access and a respect for the fragile natural environment of the islands prevent intensive field studies in this region and interpretation of data from orbital satellites and a model of lava transport provide the basic tools with which the volcanoes are studied herein. Chapter 2 presents the methodology and results ofan analysis ofSPOT-1 satellite data with a spatial resolution of 10 m, that provide complete coverage ofIslas Isabela and Fernandina. The pattern oferuption distribution on the flanks of the volcanoes indicate that the development and orientation of fascicular rift zones varies within the group and also through time on these volcanoes. The presence ofintra-caldera benches may act to inhibit the occurrence oferuptions on the adjacent segment of the volcano summit plateau. A comparison of the morphology of eruptive products in the Galapagos and Hawaii suggests that the rift zones are inefficient conduits for magma transport and storage. Chapter 3 describes the use of LANDSAT TM data covering Volcan Fernandina to investigate how the character of lava flow surfaces changes with age. These data revealed no systematic variation in the behavior of lava flow surfaces in the visible and near infrared region of the electromagnetic spectrum with age and thus no conclusions regarding the magmatic output ofVolcan Fernanadina could be made. The use of a computer model of lava flow transport to investigate the effects of volumetric discharge rate on lava flow planimetric shape is described in chapter 4. This model suggests that observed widths oflava flows in the western Galapagos Islands may be the result of volumetric discharge rates of 5 m3 sec". The difficulty of duplicating vii exactly the topography over which flows have travelledhampers the interpretation of the entireplanimetric shapein termsof theeruption charateristics. viii TABLE OF CONTENTS ACKNOWLEDGEMENTS iv ABSlRACT vi LIST OF TABLES xii LIST OF FIGURES xiv CHAPTER 1: INTRODUCTION 1 REFERENCES CITED 6 CHAPTER 2: THE APPLICATION OF SPOT-l DATA TO STIJDIES OF THE DISTRIBUTION AND CHARACTER OF ERUPTIVE MATERIALS IN THE WESTERN GALAPAGOS ISLANDS 7 2.1 INTRODUCTION 7 2.2 VOLCANISM WITHIN THE GALAPAGOS ARCHIPELAGO 7 2.2.1 The geologicalsetting of the Galapagos Islands 7 2.2.2 Petrological and geochemical characterofthe Galapagos Islands 12 2.2.3 Geochronology of the Galapagos Islands 13 2.2.4 Historical volcanicactivitywithin the Galapagos Islands 14 2.2.5 Morphology ofthe Galapagos shield volcanoes 15 2.3 RATIONALE AND METHODOLOGY FOR THE USE OF SPOT-l DATA 18 2.4 THE DISTRIBUTION OF ERUPTIVE MATERIALS 21 2.4.1 VolcanEcuador 24 2.4.2 VolcanWolf 25 2.4.3 VolcanDarwin , 27 2.4.4 VolcanAlcedo 28 2.4.5 Sierra Negra ,, 29 2.4.6 CeITO Azul 31 2.4.7 VolcanFernandina 32 ix 2.5 THE MORPHOLOGY OF ERUPTIVE PRODUCTS 34 2.5.1 The morphology of near vent deposits 35 2.5.2 Lava flow morphology 40 2.5.2.1 Planimetric shape 40 2.5.2.2 Surface textures 47 2.6 STRUCTURAL INFLUENCES ON THE ERUPTIVE BEHAVIOR OF GALApAGOS SHIELD VOLCANOES 50 2.6.1 Radial fissure distribution, the development ofrift zones, and the consequences for shield morphology 50 2.6.2 The influence of calderas on eruptive patterns 56 2.6.2.1 The morphology oferuptive fissures on the summit plateaus " 57 2.6.2.2 Intra-caldera morphology and the location of recent eruptive events 59 2.6.2.3 Caldera morphology and inferences regarding magma storage 60 2.7 MORPHOLOGICAL EVOLUTION OF THE WESTERN GALAPAGOS SIDELD VOLCANOES 67 2.8 A COMPARISON BE1WEEN THE VOLCANOES OF ISLAS FERNANDINA AND ISABELA, GALAPAGOS ISLANDS AND MAUNA LOA AND KILAUEA, HAWAII 70 2.9 CONCLUSIONS 77 REFERENCES CITED 80 CHAPTER 3: THE APPLICATION OF LANDSAT THEMATIC MAPPER DATA TO THE STUDY OF TEMPORAL PATTERNS OF VOLCANISM ON VOLCAN FERNANDINA, GALAPAGOS ISLANDS 163 3.1 INTRODUCTION 163 3.2 THE REFLECTANCE OF BASALTIC LAVA FLOWS 166 3.3 INTERPRETATION OF
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