Merapi Volcano: Geology, Eruptive Activity, and Monitoring of a High-Risk Volcano

Opening Letter: The Long Shadow of Merapi Volcano
	References
Foreword
Acknowledgements
Contents
1 The Scientific Discovery of Merapi: From Ancient Javanese Sources to the 21st Century
	Abstract
	1.1 Introduction
	1.2 Merapi in Early Javanese Sources
	1.3 The Naturalists of the 18th and 19th Century
	1.4 Observations of Merapi and Its Eruptions in the Late 19th and Early 20th Century
	1.5 Into the Modern Era: Merapi Research After Indonesia’s Independence
	1.6 The United Nations International Decade for Natural Disaster Reduction and Merapi Decade Volcano
	1.7 Research in the 21st Century
	1.8 Volcano Monitoring at Merapi—A 100 Year History
	Acknowledgements
	References
2 Physical Environment and Human Context at Merapi Volcano: A Complex Balance Between Accessing Livelihoods and Coping with Volcanic Hazards
	Abstract
	2.1 Introduction: Merapi, a Highly Populated Volcano
	2.2 The Main Reason of High Population Densities: Land Resources and Associated Livelihoods at Merapi
		2.2.1 A Climatic Context Suitable for Livelihoods
		2.2.2 Land Use, Agriculture and Livestock
		2.2.3 Block and Sand Mining in the Valleys: An Adaptation to Pyroclastic Density Currents and Lahars?
	2.3 Capacities to Face High-Frequency/Low-Magnitude Eruptions at Merapi
		2.3.1 Volcanic Risk Management
		2.3.2 Crisis Management
			2.3.2.1 Official and Traditional Warning Systems
			2.3.2.2 Organising the Evacuations: The Importance of Road Networks and Transportation Capacity
	2.4 Crisis Management and Peoples’ Responses During the 2010 Low-Frequency/High-Magnitude Eruption
		2.4.1 Crisis Management by the Authorities
			2.4.1.1 Evacuation Orders and Restricted Zones
			2.4.1.2 Crisis Management Related to Air Traffic
		2.4.2 Peoples’ Response During the 2010 Eruption Crisis
			2.4.2.1 Shelter Attendance
			2.4.2.2 Population Behaviour During the 2010 Eruption Crisis
	2.5 Post-Disaster Resilience and Adaptation at Merapi
		2.5.1 The Choice of Relocation
		2.5.2 Daily Challenges and Evolution of the Quality of Life
	2.6 Summary and Outlook
	Acknowledgements
	References
3 Merapi and Its Dynamic ‘Disaster Culture’
	Abstract
	3.1 Introduction
	3.2 The Role of the Past in the Present and Future of Merapi
		3.2.1 Misunderstandings of Past Intersections of Culture and Nature at Merapi
		3.2.2 The Colonial View of the Archaeological Site of Borobudur and Its Relationship to Merapi
		3.2.3 The Non-Colonial View of Franz Wilhelm Junghuhn on Merapi
	3.3 The Social Life of Merapi
		3.3.1 A ‘Disaster Culture’
	3.4 The Scientific Vision of Merapi
		3.4.1 Modern Scientific Study of Merapi
		3.4.2 Collecting and Disseminating Data and Interpretations in the Twenty-First Century
	3.5 The Nature and Culture of Merapi in the Anthropocene
		3.5.1 Oral Traditions and Participatory Hazards Communication as a Bridge to Scientific Communication
		3.5.2 The Sacred Axis as Pre-Modern Observation
	3.6 Engagement with Dynamic Pasts and Futures
	Acknowledgements
	References
4 The Geodynamic Setting and Geological Context of Merapi Volcano in Central Java, Indonesia
	Abstract
	4.1 Introduction
	4.2 Geodynamic Setting
	4.3 Geological Structure of Mt. Merapi
	4.4 Regional Stratigraphy of East-Central Java
		4.4.1 Basement Rocks of East-Central Java
		4.4.2 The Rembang Zone
		4.4.3 The Randublatung Zone
		4.4.4 The Kendeng Zone
		4.4.5 The Central Java Depression (Solo Zone)
		4.4.6 The Southern Mountains of East-Central Java
	4.5 Summary
	Acknowledgements
	References
5 Crustal Structure and Ascent of Fluids and Melts Beneath Merapi: Insights From Geophysical Investigations
	Abstract
	5.1 Introduction
	5.2 GPS, Tilt and Gravity Measurements
	5.3 Electrical Resistivity Structure
	5.4 Active Seismic Measurements Explain Complex Earthquake Signals of a Stratovolcano
	5.5 Merapi’s Magma Reservoir and Ascent Paths of Fluids and Partial Melts
		5.5.1 Deeper Structure Beneath Central Java
		5.5.2 Shallower Structure Beneath Merapi
	5.6 Summary
	Acknowledgements
	References
6 Geological History, Chronology and Magmatic Evolution of Merapi
	Abstract
	6.1 Introduction
	6.2 Geological Evolution of Merapi
		6.2.1 Previous Research and the Development of Ideas
			6.2.1.1 Early Work
			6.2.1.2 Research from 1980 to 2000
			6.2.1.3 Research in the Twenty-First Century
		6.2.2 A Synthesis of the Geological History and Chronology of Merapi: Current Thinking
			6.2.2.1 Volcano-Stratigraphic Units
			6.2.2.2 Structural Evolution and Volcano Collapse
	6.3 Compositional Variations of the Eruptive Products of Merapi
		6.3.1 Rock Types and Classification
		6.3.2 Mineralogy and Petrography
			6.3.2.1 Mineralogical and Petrographical Characteristics
			6.3.2.2 Mineral Textures and Compositions
		6.3.3 Major and Trace Element Compositions
		6.3.4 Isotopic Compositions
			6.3.4.1 Radiogenic Isotopes
			6.3.4.2 Oxygen Isotopes
			6.3.4.3 Uranium Series Isotopes
	6.4 Magma Genesis and Magmatic Differentiation at Merapi
		6.4.1 Magma Generation
		6.4.2 Magma Storage Conditions and Magmatic Differentiation
		6.4.3 Magmatic Evolution of Merapi: Temporal Geochemical Variations
	6.5 Summary
	Acknowledgements
	References
7 The Godean Debris Avalanche Deposit From a Sector Collapse of Merapi Volcano
	Abstract
	7.1 Introduction
	7.2 Geological Setting and Previous Studies
	7.3 Ancient Lake Borobudur
	7.4 Ancient Lake Gantiwarno
	7.5 Geology of the Godean Area
		7.5.1 Godean Palaeovolcano
		7.5.2 Godean Debris Avalanche Deposit
		7.5.3 Pyroclastic Deposits
		7.5.4 Lahar Deposits
	7.6 Significance of the Tertiary Volcanic Rocks
	7.7 Emplacement, Area Covered and Volume of the Godean Debris Avalanche Deposit
	7.8 Merapi Sector Collapse(s) and the Relation to Old Merapi and New Merapi
	7.9 Ages of Merapi Sector Collapse(s) and the Godean Debris Avalanche
	7.10 Future Hazards
	7.11 Summary and Outlook
	Acknowledgements
	References
8 The Magma Plumbing System of Merapi: The Petrological Perspective
	Abstract
	8.1 Introduction
	8.2 Geological Background
	8.3 Petrology of Merapi Lavas and Inclusions
		8.3.1 The Basaltic-Andesite Lavas
		8.3.2 Highly-Crystalline Basaltic-Andesite Schlieren and Domains
		8.3.3 Co-magmatic Basaltic Enclaves
		8.3.4 Plutonic Crystalline Inclusions
		8.3.5 Amphibole Megacrysts
		8.3.6 Metasedimentary Calc-Silicate Inclusions (Crustal Xenoliths)
	8.4 A View into the Magma Plumbing System of Merapi
		8.4.1 Evidence from Thermobarometry
		8.4.2 Evidence from Phase-Equilibrium Experiments
		8.4.3 Rare Earth Element Concentrations and Patterns
		8.4.4 Radiogenic Isotopes
		8.4.5 Oxygen and Deuterium Isotopes
		8.4.6 Constraints from Geophysics and Thermobarometry Approaches
	8.5 Magma Storage and Origin of Inclusions and Xenolith Types
	8.6 An Integrated Model for Merapi’s Plumbing System
	8.7 Magma Storage Along the Java-Bali Segment of the Sunda Arc
	8.8 Summary and Outlook
	Acknowledgements
	References
9 A Textural Perspective on the Magmatic System and Eruptive Behaviour of Merapi Volcano
	Abstract
	9.1 Introduction
	9.2 Background
		9.2.1 Eruptive Styles of Merapi
		9.2.2 Merapi Magmatic System
		9.2.3 Crystallisation: Nucleation, Growth and Equilibrium Effects
		9.2.4 Crystal Size Distribution (CSD) Analysis
	9.3 The Crustal Plumbing System and Magmatic Processes Revealed Through Textural Analysis
		9.3.1 Coarse Plutonic Inclusions and the Deep Plumbing System
		9.3.2 Phenocrysts: Crustal Magma Storage System and Its Evolution Through Time
	9.4 Shallow Conduit Processes Revealed Through Textural Analyses
		9.4.1 Amphibole Reaction Rims
		9.4.2 Feldspar Groundmass Microlite Textures
			9.4.2.1 Feldspar Microlite Textures in Effusive Dome-Forming Eruptions
			9.4.2.2 Effusive—Explosive Transitions at Merapi: Textural Evidence
	9.5 Summary and Outlook
	Acknowledgements
	References
10 Magma-Carbonate Interaction at Merapi Volcano, Indonesia
	Abstract
	10.1 Introduction
	10.2 A Brief History of Research on Magma-Carbonate Interaction
	10.3 Geological Context of Merapi
	10.4 Mineralogy of Merapi Calc-Silicate Xenoliths
	10.5 Geochemical Evidence of Magma-Carbonate Interaction
		10.5.1 Strontium Isotopes
		10.5.2 Oxygen Isotopes
		10.5.3 Carbon and Helium Isotopes
		10.5.4 A Major Element Conundrum?
	10.6 Experimental Magma-Carbonate Interaction at Merapi
		10.6.1 Volatile Degassing
		10.6.2 Calcium-Contamination
	10.7 The Volatile Budget at Merapi
	Acknowledgements
	References
11 Merapi Volcano: From Volcanic Gases to Magma Degassing
	Abstract
	11.1 Introduction
	11.2 Early Analyses of Merapi Volcanic Gases
		11.2.1 Major Gas Chemistry
		11.2.2 Stable Isotope Tracing
		11.2.3 Trace Elements
	11.3 Routine Survey of Merapi Volcanic Gases
		11.3.1 Gas Composition
		11.3.2 Sulphur Dioxide Emission Rate
	11.4 Degassing of Resident Magma in Shallow Feeding System
	11.5 Merapi Hydrothermal System
	11.6 Magma-Limestone Interaction and CO2 Degassing
	11.7 Volcanic Gas Composition and Eruptive Activity
		11.7.1 Pre-eruptive Gas Changes and Eruption Style
		11.7.2 Dome Growth and Gas Composition
		11.7.3 Volcanic Activity and Trace Metals in Gases
	11.8 Volatiles at the Roots of the System
	11.9 Synthetic Models
	11.10 Regional Seismicity, Volcanism and Degassing
	11.11 Volatiles and Triggering Mechanism of the 2010 Eruption
	11.12 Atmospheric Impacts
	11.13 Summary and Outlook
	Acknowledgements
	References
12 An Overview of the Large-Magnitude (VEI 4) Eruption of Merapi in 2010
	Abstract
	12.1 Introduction
	12.2 Eruption Chronology
		12.2.1 Reawakening of Merapi and Volcanic Unrest
		12.2.2 Beginning of the Eruption and Pre-Climactic Activity
		12.2.3 Climactic Eruption Phase
		12.2.4 Post-Climactic Activity and End of the 2010 Eruption
	12.3 The Volcano Monitoring Record of the 2010 Eruption
		12.3.1 Seismicity
		12.3.2 Ground Deformation
		12.3.3 Gas Geochemistry
		12.3.4 Physical Processes Prior to the Eruption
	12.4 Volcanic Deposits of the 2010 Eruption
		12.4.1 Types, Volume and Distribution of the 2010 Volcanic Deposits
		12.4.2 Volcanic Deposits Linked to Eruption Chronology
		12.4.3 Generation, Dynamics and Significance of High-Energy Pyroclastic Density Currents
	12.5 Geochemistry and Petrology of the 2010 Eruptive Products
		12.5.1 Rock Types and Classification
		12.5.2 Petrography and Mineral Chemistry
		12.5.3 Magma Storage and Magmatic Processes
		12.5.4 Timescales of Magmatic Processes
	12.6 Eruption Effects, Impact and Recovery
	12.7 Managing the 2010 Volcanic Crisis
		12.7.1 The Role of the National Disaster Management System in Indonesia
		12.7.2 Vulnerability Before the 2010 Eruption
		12.7.3 Disaster Risk Reduction Strategy
			12.7.3.1 Strengthening of the Volcano Monitoring System During the 2010 Eruption Crisis
			12.7.3.2 Formation of a Disaster Risk Reduction Forum: The Merapi Forum
			12.7.3.3 Strengthening of Community Capacity Through Disaster Management Training and Information Dissemination
			12.7.3.4 Preparation of Contingency Plans
		12.7.4 International Collaboration
		12.7.5 Reflection and Lessons Learned
	12.8 Summary
	Acknowledgements
	References
13 The Merapi Volcano Monitoring System
	Abstract
	13.1 Introduction
	13.2 Volcano Monitoring at Merapi: 1920–2010
	13.3 The Merapi Monitoring Network After 2010
		13.3.1 Real-Time Instruments
		13.3.2 Temporary Experiments
	13.4 Data Handling and Monitoring Tools
		13.4.1 Cendana15: Integrated Collaborative Work Management Application
		13.4.2 The WOVOdat Platform
		13.4.3 The WebObs System
		13.4.4 Support System for Decision Making (SSDM)
		13.4.5 MAGMA Indonesia
	13.5 Perspectives
		13.5.1 Deep Magma Reservoir Monitoring
		13.5.2 Modelling of Common Physical Parameters from Multidisciplinary Methods
		13.5.3 Machine Learning
		13.5.4 Crisis Management
	Acknowledgements
	References
14 Radar Sensing of Merapi Volcano
	Abstract
	14.1 Introduction
	14.2 Synthetic Aperture Radar
		14.2.1 SAR Geometry
		14.2.2 Satellite SAR Systems
	14.3 SAR Applications at Merapi
		14.3.1 Amplitude Methods and Analysis
		14.3.2 Phase Differencing Methods and Analysis
		14.3.3 Other Applications of SAR Systems
	14.4 Summary and Outlook
	Acknowledgements
	References
15 Morphology and Instability of the Merapi Lava Dome Monitored by Unoccupied Aircraft Systems
	Abstract
	15.1 Introduction
	15.2 Methods
		15.2.1 Unoccupied Aircraft Systems (UAS)
		15.2.2 Photogrammetry and Structure From Motion (SfM)
	15.3 Repeat Surveys of the Summit of Merapi Using Unoccupied Aircraft Systems
		15.3.1 Drone Flight 2012: Morphology and Structure of the Merapi Lava Dome
		15.3.2 Drone Flight 2015: Changes Associated with Steam-Driven Explosions
		15.3.3 Drone Flight 2017: Changes Associated with Hydrothermal Activity
		15.3.4 Drone Flight 2019: Changes Associated with a New Dome Growth Episode
	15.4 Monitoring Lava Dome Building Activity and Morphological Changes in the Summit Area of Merapi Using Repeat Unoccupied Aircraft Systems Surveys
	15.5 Summary and Outlook
	Acknowledgements
	References
16 Assessing the Pyroclastic Density Current Hazards at Merapi: From Field Data to Numerical Simulations and Hazard Maps
	Abstract
	16.1 Pyroclastic Density Current (PDC) Hazards at Merapi
	16.2 Hazard Assessment of Pyroclastic Density Currents at Merapi
		16.2.1 Field Data Acquisition and Processing
		16.2.2 Numerical Models of PDCs and Their Approaches
		16.2.3 Deterministic Versus Probabilistic PDC Hazard Modelling Approaches
		16.2.4 The Merapi Volcanic Hazard Map
	16.3 Case Study 1: Field Data Acquisition and Numerical Simulations of the 2006 PDCs
		16.3.1 Summary of the 2006 Eruptive Events
		16.3.2 Numerical Simulations of the 2006 Block-And-Ash Flow Events
			16.3.2.1 Simulations of Short- to Medium-Runout 2006 Block-And-Ash Flows (SM-BAF)
			16.3.2.2 Simulations of Long-Runout 2006 Block-And-Ash Flows (L-BAF)
			16.3.2.3 Evaluation of Simulation Results
	16.4 Case Study 2: Field Data Acquisition and Numerical Simulations of the 2010 Pyroclastic Density Currents
		16.4.1 Chronology of the Eruption
		16.4.2 The Two-Layer Model
		16.4.3 Emplacement of the 5 November Pyroclastic Density Currents
		16.4.4 Evaluation of Simulation Results
	16.5 Towards an Integration of Numerical Modelling Results into Hazard Maps
	Acknowledgements
	References
17 Merapi’s Lahars: Characteristics, Behaviour, Monitoring, Impact, Hazard Modelling and Risk Assessment
	Abstract
	17.1 Introduction
		17.1.1 Terminology and Scope
		17.1.2 Population at Risk
	17.2 Merapi, Java’s Largest Lahar Producer
		17.2.1 Lahar Triggering at Merapi
		17.2.2 Why is Merapi Prone to Producing Lahars?
		17.2.3 Lahar Activity Following the 2010 VEI 4 Eruption
	17.3 Lahar Monitoring and Warnings at Merapi
		17.3.1 Monitoring Instrumentation
		17.3.2 Warning System
	17.4 Lahar Behaviour and Dynamics at Merapi
		17.4.1 Direct Measurement
		17.4.2 Sedimentological and Hydraulic Analysis
		17.4.3 Remote Sensing, DEM and Channel Morphometry Analysis
	17.5 Geophysical Measurements
		17.5.1 Early Experimental Measures
		17.5.2 Signal Characteristics
		17.5.3 Recent Geophysical Measurements in the Kali Gendol Valley
		17.5.4 Combining Measurements: 28 February 2014 Lahar Event
	17.6 Lahar Impact
	17.7 Revised Lahar-Prone Maps and Modelling Lahar Inundation Extent and Impact
		17.7.1 LAHARZ Modelling
		17.7.2 New Developments in Lahar Modelling Using the FLO2D Code
	17.8 Assessment of Lahar Risk
	17.9 Summary
	Acknowledgements
	References
18 Merapi: Evolving Knowledge and Future Challenges
	Abstract
	18.1 Introduction
	18.2 Geology and Volcanic History
	18.3 Petrogenesis, Magma Plumbing System and Magmatic Processes
	18.4 Eruptions and Transitions in Eruptive Style
	18.5 Volcano Monitoring
	18.6 Early Warning System
	18.7 Emergency Planning and Volcanic Crisis Management
	18.8 Social and Communication Changes
	18.9 International Collaboration
	18.10 Post-2010 Activity and Current Status of Merapi
	References