Monitoring and Modelling Volcanoes with Assessment of Their Hazards by Means of Remote Sensing and Analogue Modelling
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FACULTY of SCIENCES Department of Geology and Soil Sciences Monitoring and modelling volcanoes with assessment of their hazards by means of remote sensing and analogue modelling by Matthieu KERVYN 2008 Thesis submitted in fulfilment of the requirements for the degree of Doctor in Science, Geology Promoter: Prof. Dr. Patric Jacobs Co-promoter: Dr. Gerald G.J. Ernst Monitoring and modelling volcanoes with assessment of their hazards by means of remote sensing and analogue modelling Monitoring en modellering van vulkanen met evaluatie van hun risico’s door middel van afstandwaarneming en analoge modellen by Matthieu KERVYN 2008 PhD Review Committee Other Jury Members Prof. Dr. P. Jacobs (UGent, Promoter, Prof. Dr. J.-P. Henriet (UGent, Chairman) Secretary) Prof. Dr. E. van Ranst (UGent) Dr. G.G.J. Ernst (UGent, Co-promoter) Prof. Dr. M. Elburg (UGent) Prof. Dr. B. van Wyk de Vries Prof. Dr. R. Goossens (UGent) (LMV, UBlaise Pascal, Clermont-Ferrand) Prof. Dr. M. Fernandez-Alonso (KMMA) Prof. Dr. J. Keller (UFreiburg) Prof. Dr. A.J.L Harris (UHawaii) Cover photo: Active crater of Oldoinyo Lengai volcano on May 21, 2006, viewed from South. This study was supported by the Research Foundation – Flanders Fonds voor Wetenschappelijk Onderzoek – Vlaanderen Written at: Department of Geology and Soil Science Ghent University Krijgslaan 281/S8 B-9000 Ghent, Belgium Acknowledgments I would first like to thank my promoter, Prof. Patric Jacobs, for his continuous support during these last four years. His determination to develop a volcanology unit and an analogue laboratory, and his guidance helped me immensely during my research. My sincere acknowledgments also go to my co-promoter, close colleague and friend, Dr. Gerald G. J. Ernst. Our collaboration and complementary research, his great enthusiasm and our animated discussions always encouraged me to go deeper in the understanding of processes and to propose innovative interpretations. I am grateful to my volcanologist colleagues Dr. Mary-Ann del Marmol and Karen Fontijn, and all the MSc students involved in research projects with me: Nele Tytgat, Annelies Decraene, Isolde Belien, Cilia Derese, Ann Zwertvaegher, Kathelijne Bonne, Charissa Stevens, Bernd Rombaut, Christelle Wauthier and David Goetheyn. All of them contributed to create a positive and stimulating research environment in the volcanology group. Thank you also to my colleagues of the Geology and Geography departments who each, with their own expertise and talents, helped me to be better integrated at UGent and to develop my research. I especially would like to thank Dr. Veerle Cnudde, Elin Vanlierde, Koen Pieters, Nina Smeyers, Kurt Blom, and also Prof. E. Van Ranst, Prof. R. Goossens, Prof. A. De Wulf, Marc Hennau, Tony Vanderstraete and Gilberte Verschueren. Michael Gentbrugge and his team are especially acknowledged for their help in developing experimental setups for the analogue laboratory. It was also a pleasure to interact with colleagues from the Royal Museum for Central Africa, including Dr. Johan Lavreau, Dr. Philippe Trefois, Dr. Damien Delvaux, Dr. Max Fernandez-Alonso. Dr. François Kervyn is especially thanked for his continuous interest for African volcanoes and for introducing me to the geology of Tanzania during a joined field trip to Oldoinyo Lengai. My research on Oldoinyo Lengai gave me the chance to develop close links with several experts of this unique volcano. I thank Prof. Joerg Keller and Dr. Jurgis Keller for sharing their field knowledge and their data on debris avalanches. Frederic Belton, Chris Weber, Célia Nyamweru, and Hugh Anderson are also acknowledged for sharing key data and observations and discussing the hazards at Oldoinyo Lengai. Tanzanian colleagues from the University of Dar-es-Salaam, Prof. E. Mbede and Majura Songho, and from the Tanzania Geological Survey, F. Petro, greatly helped to prepare and conduct the field trip at Oldoinyo Lengai, together with local Masais. Karim Kelfoun is deeply thanked for providing access and helping with the use of the VolcFlow model. I am also thankful to all who contributed with observations and photographs of Oldoinyo Lengai activity including Dean Polley, Matt Jones, UDSM staff members, David Peterson, Daniela Szczepanski, Bernard Duycks, R. Rosen, Thierry Sluys, Michael Dalton-Smith, Bernard Masson (LAVE Belgique), Chris Weber, Rohit Nandedkar, Tim iii Acknowledgment Leach, Thomas Holden and especially Benoît Wihelmi, who provided fantastic airplane pictures of Oldoinyo Lengai during the 2007-08 eruption. I am very grateful to Prof. Benjamin van Wyk de Vries for welcoming me in his laboratory at the Laboratoire Magma et Volcans in Clermont Ferrand (France). His will to share his experience and his enthusiasm greatly encouraged me to develop this aspect of my research. His students Lucie Mathieu and Céline Dumaisnil, and the staff members of LMV, are acknowledged for their stimulating discussions and help in the lab. The research presented here also benefited from collaborations or discussions with other volcanologists including Dr. Andrew Harris, Dr. Rob Wright, Dr. S. Rowland, from University of Hawaii (USA) and Prof. Dave Rothery, from Open University (UK), regarding thermal monitoring of volcanoes and Prof. Valentine Troll (Trinity College, Dublin), Prof. Valerio Acocella (University of Roma, Italy) Prof. Thomas Walter (GFZ Postdam, Germany) and Dr. Olivier Galland (University of Oslo, Norway) for analogue modelling. Prof. Samuel Ayonghe and Prof Emmanuel Suh, from University of Buea (Cameroon), Prof. Richard Teeuw (University of Portsmouth, UK), Dr. Carsten Riedel, and Collin Nkono (ULB) are acknowledged for discussing several aspects of my research and contributing with useful data. Prof. Juan-Carlos Carracedo is greatly acknowledged for providing very high resolution data for Lanzarote and for introducing me to the rich geology of this Canarian Island. All this research would not have been possible without the financial support of the Fonds voor Wetenschappelijk Onderzoek – Vlaanderen. Field trips were also partly supported by an Award from the Fondation belge de la Vocation and by a scholarship from the VLIR. Thank you to my friends Olivier Evrard and David Dabin who shared their own experience of a PhD and who provided useful reviews of my publications. Thank you also to my parents and brothers for understanding and supporting my interest in volcanology. Finally, my deepest thanks go to my wife, Céline, for her love, her patience, her interest and her encouragements. iv Contents Acknowledgments iii Contents v List of Figures viii List of Tables xi List of Abbreviations xii Introduction 1 PART I. REMOTE SENSING AND TOPOGRAPHIC MODELLING OF POORLY-KNOWN VOLCANOES 5 Chapter 1. Mapping, Monitoring and Assessing Hazards at Volcanoes: A Review 7 1.1. Multispectral and DEM data 10 1.1.1 Landsat 10 1.1.2 ASTER 11 1.1.3 SPOT 12 1.2. Satellite radar systems 13 1.2.1 Synthetic Aperture Radar (SAR) 13 1.2.2 SAR Interferometry 14 1.2.3 InSAR Monitoring 15 1.2.4 SRTM and InSAR Topography 16 1.3. Conclusions 17 Chapter 2. Assessment of Accuracy of ASTER and SRTM DEMs 19 2.1. Data set 20 2.2. DEM spatial resolution: Effect on height estimate 22 2.3. Mauna Kea 26 2.3.1 Data processing 27 2.3.2 Accuracy assessment 29 2.4. Oldoinyo Lengai 34 2.4.1 Data processing 34 2.4.2 Accuracy assessment 37 2.5. Discussion and conclusion 41 PART II. MONITORING ACTIVITY AND ASSESSING HAZARDS AT OLDOINYO LENGAI, TANZANIA 45 Chapter 3. Oldoinyo Lengai: A unique Natrocarbonatite Volcano 47 Chapter 4. Sector Collapses and Debris-Avalanche Deposits at Oldoinyo Lengai and Kerimasi 53 4.1. Datasets and method 54 4.2. OL Structure, Topography and Volume 55 4.2.1 Structural evolution and petrography 55 4.2.2 RS Observations 55 4.2.3 Estimation of OL’s volume 56 4.3. Debris-avalanche deposits 58 v Contents 4.4. Zebra Debris-Avalanche 58 4.4.1 Field Observations 58 4.4.2 RS observations 59 4.5. Oryx Debris-Avalanche Deposit 68 4.5.1 Field observations 68 4.5.2 RS observations 68 4.6. Cheetah Debris- Avalanche Deposit 69 4.6.1 Field observations 69 4.6.2 RS observations 69 4.7. Kerimasi Debris-Avalanche Deposit 72 4.8. Other potential DADs 74 4.9. Discussion 74 4.9.1 General morphological considerations 74 4.9.2 Collapse sources and triggering mechanisms 75 4.9.3 Collapse Orientation 76 4.9.4 Debris-Avalanche Mobility 77 4.9.5 Some constraints on debris-avalanche flow 79 4.9.6 Numerical simulation of the Cheetah debris-avalanche 79 4.9.7 Implications for hazards 87 4.10. Conclusions 88 Chapter 5. Thermal Remote Sensing of the low-intensity Carbonatite Volcanism 89 5.1. Thermal emissions of Oldoinyo Lengai 89 5.2. MODVOLC and thermal monitoring 94 5.3. MODLEN: An adapted algorithm 96 5.3.1 Subscene selection and extraction 97 5.3.2 NTI threshold 97 5.3.3 Spatial derivative 97 5.3.4 Baseline data record 98 5.4. MODLEN Validation 101 5.4.1 August 2002 101 5.4.2 July 2004 102 5.4.3 July 2005 108 5.5. MODLEN Results 108 5.6. Discussion 113 5.6.1 Environmental controls on OL activity 113 5.6.2 MODLEN limitations 115 5.7. Conclusions 117 Chapter 6. Voluminous Lava Flows at Oldoinyo Lengai in 2006: Chronology of Events and Insights into the shallow magmatic System 119 6.1. Accounts of the March-April eruption: Field and news reports 119 6.2. Thermal RS observations 126 6.3. Field observations 127 6.3.1 A new collapse pit 127 6.3.2 New lava field in the crater 130 6.3.3 West flank lava flows 132 6.3.4 Evolution after May 2006: Transition to explosive volcanism 133 6.4. Composition of March-April 2006 lavas 136 6.4.1 Petrographic description 136 6.4.2 Chemical composition 137 6.5.