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Airborne Remote Sensing of Grimsvotn Subglacial Volcano, Vatnajokull, Iceland

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Airborne Remote Sensing of Grimsvotn Subglacial Volcano, Vatnajokull, Iceland Airborne remote sensing of Grimsvotn subglacial volcano, Vatnajokull, Iceland A thesis presented in fulfilment of the requirements for the degree of Doctor of Philosophy by Sukina Stewart BSc (Cardiff) 1998 PGCE (Keele) 1999 Environmental Science Department Lancaster University Geography Department Lancaster University February 2006 ProQuest Number: 11003689 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 11003689 Published by ProQuest LLC(2018). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 © 2 006 SUKINA FAITH STEWART ALL RIGHTS RESERVED Grimsvotn caldera lake, in the area of the 1998 eruption crater, June 2004. (Photograph by S. Stewart) •?£ Acknowledgments First and foremost I must thank my supervisors. Thank you to Harry Pinkerton for initiating the project, for your support, hours of reading my chapters and putting up with my grumbles. His knowledge and expertise were invaluable. Thank you to Alan Blackburn for hours of reading my chapters, introducing me to remote sensing, and finding me space in the Geography department where I have been very happy for the last three years. In the last few months both supervisors have found the time to read my draft chapters and make useful suggestions. Thank you to the NERC ARSF for collecting the data and accepting the proposal without which there would be no project. Thank you in particular to Bill Mockridge and Andrew Wilson who provided valuable support for the geocorrection of the imagery and the AZGCORR programme. Thank you to Magnus Gubmundsson for inviting me to join the Icelandic Glaciological Society annual trip to Grimsvotn, and for finding me accommodation and feeding me on a number of occasions whilst I was in Iceland, along with many useful discussions. And to Tolli, Disa and Finnur P. for helping me to adjust to Icelandic life. Thank you also to Agust Halfdansson for providing me with accommodation for a couple of days at the end of the trip and helping me to adjust to life on the glacier. For the invaluable support in GIS and RS and computers generally, as well as being a great office mate I must thank Gemma Davies. Also, Paul Williams for IT support on those rare occasions when my computer went awry, e.g. when hard drive died during writing up. Thank you to Ian Jones in CEH Lancaster, for the useful discussions and assistance on heat flux. Thanks also go to Matt Ball for taking the time to assist with the radiation to temperature conversion, along with being a great housemate and landlord. Plus I’m grateful to the following for all their useful comments and discussions: Jennie Gilbert, Steve Lane, Mike James, Hugh Tuffen, John Stevenson, Steve Corder and Rodrigo del Potro. Thank you to Rhian Burrell, Emmanuel Otoo and Claire Ellender for all those supportive chats, grumbles and coffees. Finally thank you to my family for supporting me in my decision to give up my career to do this and for all their love and support through the ups and downs that I’ve encountered over the last few years. Thank you all. A bstract Grimsvotn, a subglacial volcano in Iceland, has a partially exposed geothermal system, that has, until recently, been used to make estimates of heat flux using calorimetry. Increased melting in Grimsvotn in the aftermath of the 1998 eruption has changed the ice conditions considerably, resulting in major leakage of the ice dam that used to seal Grimsvotn caldera lake. This makes calorimetric estimates of melting more difficult. An aerial survey of Grimsvotn was carried out in June 2001. Thermal images of the Grimsvotn subglacial caldera show distinct areas of geothermal activity. Ground survey studies of the same area carried out by the Science Institute, University of Iceland, show that protruding ground above the ice, along with areas of open water, have high geothermal heat flux all year round. In these areas, heat is lost by radiation and geothermal steam emission. This component of heat flux cannot be detected by calorimetric estimates based on ice melting. Therefore an alternative method of calculating heat flux is adopted in this research based on a combination of remote sensing and meteorological information. Aerial photographs collected for Grimsvotn have been used to map the main features along the caldera walls, such as crevasses and slumps that cannot be accurately mapped from the ground because of inaccessibility. A high resolution DEM of the case study sites has been generated from the aerial photographic coverage using a stereoscope and parallax bar. The combined data sets have been analysed both visually and quantitatively using a combination of ERDAS Imagine and ARCGIS environments. Together, these data establish that remote sensing can be used to map and monitor an inaccessible volcano such as Grimsvotn, as well as aid in the understanding of the processes at work within one of the most powerful geothermal systems in the world. Contents Acknowledgments.......................................................................................................................i Abstract........................................................................................................................................ii Contents.......................................................................................................................................iv List of Tables............................................................................................................................... x List of Figures............................................................................................................................. x Chapter 1 - Introduction........................................................................................................ 1 1.1. Introduction ...................................................................................................................... 1 1.2. Importance of study ........................................................................................................ 1 1.3. Aims of the PhD ..............................................................................................................3 1.4. Structure of the thesis .....................................................................................................5 Chapter 2 - Volcanological Aspects of Subglacial Eruptions.........................................6 2.1. Introduction ......................................................................................................................6 2.2. Subglacial Eruption Processes......................................................................................7 2.3. Global Subglacial Studies ............................................................................................. 9 2.3.1. Antarctica ........................................................................................................ 10 2.3.2. Canada ..............................................................................................................12 2.3.3. Alaska...............................................................................................................12 2.4. Effect of Ice Thickness on Eruption Characteristics .............................................. 13 2.5. Related Processes ...........................................................................................................16 2.5.1. Subglacial seismicity .....................................................................................16 2.5.2. Pillow lavas ..................................................................................................... 19 2.5.3. Gas driven eruptions ......................................................................................20 2.5.4. Ice melting .......................................................................................................21 2.5.5. Melt water transport ....................................................................................... 25 2.5.6. Volcanic crater lakes .....................................................................................28 2.5.7. Calorimetry and heat flux ............................................................................. 29 2.6. Summary....................................................................................................................... 30 Chapter 3 - Principles of Remote Sensing and Photogrammetry: Applications in Volcanology and Terrain Analysis.............................32 3.1. Introduction ...................................................................................................................32 3.2. Electromagnetic Spectrum .........................................................................................32 3.3. Thermal emission ........................................................................................................ 35 3.4. Using Remote Sensing to measure emissivity .......................................................37 3.5. Interaction of EM radiation with water ..................................................................
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