Fundamentals of Physical Volcanology

Elisabeth Parfitt was previously a lecturer in Physical Volcanology at the University of Leeds and an Honorary Research Fellow at Lancaster University in the UK. She also spent time in the USA as a Research Scientist at Brown University and at the State University of New York at Buffalo. She currently works as an Archivist in North Wales. Lionel Wilson is Emeritus Professor of Earth and Planetary Sciences at Lancaster University, UK. He is also a Visiting Professor at the University of Hawai‘i and Brown University in the USA. Laura Kerber is a Research Scientist at NASA’s Jet Propulsion Laboratory and a Visiting Associate in Planetary Sciences at the California Institute of Technology.

• Preface xiiiAcknowledgments xvGlossary xvii1 Volcanic Systems 11.1 Introduction 11.2 Styles of Volcanic Eruptions 11.2.1 Effusive Eruptions 21.2.2 Hawaiian-Style Eruptions 31.2.3 Flood Basalt Eruptions 41.2.4 Plinian Eruptions 51.2.5 Ignimbrite-Forming Eruptions 61.2.6 Strombolian Eruptions 71.2.7 Vulcanian Eruptions 91.2.8 Hydromagmatic Eruptions 101.2.8.1 Deep Marine Environments 101.2.8.2 Lava Flows Entering Water 101.2.8.3 Shallow Marine and Crater Lake Eruptions 111.2.8.4 Subglacial Eruptions 121.2.8.5 Interactions with Groundwater 131.2.9 Diatreme-Forming Eruptions 131.3 Volcanic Systems 141.4 The Structure and Aims of This Book 161.5 Further Reading 161.6 Questions to Think About 172 Magma Generation and Segregation 192.1 Introduction 192.2 Rock-Melting Mechanisms 192.3 Volcanism and Plate Tectonics 202.3.1 Tectonic Settings, Melting Processes, and Magma Composition 232.3.1.1 Mid-Ocean Ridges and Oceanic Intraplate Settings 232.3.1.2 Continental Intraplate Settings 252.3.1.3 Subduction Zones – Island Arcs and Continental Arcs 252.4 Melting and Melt Segregation in the Mantle 272.4.1 Nature of the Mantle 272.4.2 Onset of Mantle Melting 282.4.3 Melt Migration 292.5 Summary 312.6 Further Reading 312.7 Questions to Think About 323 Magma Migration 333.1 Introduction 333.2 Diapiric rise of Melt 333.3 The Change From Diapir Rise to Dike Formation 343.4 Dike Propagation 353.5 Trapping of Dikes 373.6 Consequences of Dike Trapping 413.7 Summary 423.8 Further Reading 443.9 Questions to Think About 444 Magma Storage 454.1 Introduction 454.2 Evidence for Magma Storage Within the Crust 454.2.1 Structural Evidence Provided by Calderas 454.2.2 Petrological Evidence in Lava Flows 464.2.3 Geophysical Evidence 484.2.3.1 Seismic Techniques 484.2.3.2 Gravity and Magnetotelluric Techniques 494.2.3.3 Deformation Techniques 514.2.4 Geological Evidence From Exposed Intrusions 534.3 Formation and Growth of Magma Reservoirs 554.4 Magma Reservoirs and Their Impact on Volcanic Systems 624.4.1 Fractionation in Magma Reservoirs 624.4.2 Regulation of Eruption Frequency and Magnitude 634.4.3 Volatiles and Chamber Failure 654.5 Summary 664.6 Further Reading 674.7 Questions to Think About 675 The Role of Volatiles 695.1 Introduction 695.2 Volatiles in Magma 695.3 The Solubility of Volatiles in Magma 705.4 Bubble Nucleation 735.5 Bubble Growth 745.5.1 Growth by Diffusion 745.5.2 Growth by Decompression 745.5.3 Bubble Coalescence 755.6 Influence of Volatiles on Magma Dynamics 785.7 Magma Fragmentation and the Influence of Volatiles on Eruption Styles 795.8 Summary 815.9 Further Reading 825.10 Questions to Think About 826 Steady Explosive Eruptions 836.1 Introduction 836.2 Influence of Gas Bubbles Prior to Magma Fragmentation 836.3 Acceleration of the Gas–Magma Mixture 846.4 Controls on Exit Velocity 866.4.1 Magmatic Gas Content and Exit Velocity 866.4.2 Dike Shape, Vent Geometry, and Exit Velocity 876.5 Eruption Plumes in Steady Eruptions 886.5.1 Plume Rise 896.5.2 Controls on Plume Height 916.6 Fallout of Clasts from Eruption Plumes 916.6.1 Rise of Clasts in an Eruption Plume 916.6.2 Fallout of Clasts from Eruption Plumes 936.7 Unstable Eruption Columns 936.7.1 Plume Density and Column Stability 946.7.2 Causes of Column Instability 946.8 Summary 966.9 Further Reading 976.10 Questions to Think About 987 Transient Volcanic Eruptions 997.1 Introduction 997.2 Magmatic Explosions 997.2.1 Modeling Transient Magmatic Explosions 1007.2.1.1 Relating Vent Pressures to Eruption Velocities 1007.2.1.2 Predicting the Range of Ballistic Clasts 1027.2.1.3 Plume Heights in Transient Eruptions 1057.3 Transient Eruptions Involving External Water 1067.3.1 Types of Hydromagmatic Eruptions 1067.3.2 Mechanisms of Violent Magma–Water Interactions 1087.3.3 Tephra from Hydromagmatic Eruptions 1087.4 Summary 1087.5 Further Reading 1097.6 Questions to Think About 1098 Pyroclastic Falls and Pyroclastic Density Currents 1118.1 Introduction 1118.2 Fallout of Clasts from Eruption Columns 1118.2.1 Fallout from the Rising Eruption Column 1118.2.2 Fallout from the Umbrella Region 1138.2.3 Fall Speeds of Pyroclasts 1138.2.4 Other Factors Affecting Fallout from Eruption Columns 1158.2.5 Common Features of Fall Deposits 1168.3 The Application of Eruption Column Models 1178.3.1 Analyzing a Fall Deposit 1178.3.2 Estimating the Eruption Rate and the Eruption Speed 1188.3.3 Finding the Wind Speed 1208.3.4 Finding the Fall Deposit Volume and the Eruption Duration 1218.3.5 Fall Deposits: Summary 1218.4 Pyroclastic Density Currents and Their Deposits 1228.4.1 Origins of Pyroclastic Density Currents 1228.4.1.1 Column Collapse and Pyroclastic Fountaining 1228.4.1.2 Directed Blasts and Collapses from Lava Domes and Flows 1238.4.2 Pyroclastic Density Current Emplacement Processes 1248.4.3 Nature of the Deposits 1288.5 Summary 1298.6 Further Reading 1308.7 Questions to Think About 1319 Lava Flows 1339.1 Introduction 1339.2 Origin of Lava Flows 1339.3 Types of Lava Flows 1339.4 Lava Flow Rheology 1389.5 Rheological Control of Lava Flow Geometry 1409.6 Lava Flow Motion 1439.7 Lengths of Lava Flows 1449.8 Surface Textures of Lava Flows 1459.9 Effects of Ground Slope and Lava Viscosity 1499.10 Summary 1499.11 Further Reading 1519.12 Questions to Think About 15110 Eruption Styles, Scales, and Frequencies 15310.1 Introduction 15310.2 Chemical Composition and Styles of Volcanic Activity 15310.3 Chemical Composition and Effusive Eruptions 15510.3.1 Conditions of Effusive Eruption 15510.3.2 Chemical Composition and Lava Flows 15710.4 Chemical Composition and Explosive Eruptions 15710.4.1 Transient and Sustained Explosive Activity 15710.4.2 Chemical Composition and Transient Explosive Activity 15810.4.3 Chemical Composition and Sustained Explosive Eruptions 16010.4.3.1 Role of Viscosity 16010.4.3.2 Role of Gas Content 16110.5 Summary of Compositional Controls on Eruption Character 16110.6 Magnitudes and Frequencies of Volcanic Eruptions 16310.6.1 The Magnitude of Historic Volcanic Eruptions 16310.6.2 The Magnitude of Volcanic Eruptions in the Geological Record 16610.6.3 The Frequency of Volcanic Eruptions 16710.6.4 Magma Reservoirs and Eruption Magnitude and Frequency 16710.7 Elastic and Inelastic Eruptions and the Contribution of “Mush” 16810.8 Eruptions of Exceptional Magnitude 17110.8.1 Introduction 17110.8.2 Large Ignimbrite-Forming Eruptions 17110.8.3 Flood Basalt Eruptions 17110.9 Summary 17210.10 Further Reading 17310.11 Questions to Think About 17411 Volcanic Hazards and Volcano Monitoring 17511.1 Introduction 17511.2 Types of Volcanic Hazards 17511.2.1 Lava Flows 17511.2.2 Pyroclastic Falls 17611.2.3 Ash in the Atmosphere 17811.2.4 Pyroclastic Density Currents and Surges 17911.2.5 Lahars 18011.2.6 Jökulhlaups 18111.2.7 Volcanic Gases 18211.3 Hazard Assessment 18311.4 Monitoring Volcanoes and Short-term Eruption Prediction 18511.5 Hazard Mitigation 18811.6 Summary 18911.7 Further Reading 18911.8 Questions to Think About 19012 Volcanoes and Climate 19112.1 Introduction 19112.2 Evidence for the Impact of Volcanic Eruptions on Climate 19112.3 Satellite Monitoring of Climate Change After Volcanic Eruptions 19412.4 The Effects of Volcanic Eruptions on Climate 19512.4.1 The Influence of Plume Height on Climate Change 19612.4.2 The Effect of Geographical Location on Climate Impact 19612.4.3 The Effects of Eruption Volume on Climate Impact 19612.4.4 The Effects of Magma Composition on Climate Impact 19812.4.5 The Effects of Eruption Duration on Climate Impact 19812.5 Volcanoes and Mass Extinctions 19912.6 Summary 20012.7 Further Reading 20112.8 Questions to Think About 20113 Volcanism on Other Planets 20313.1 Introduction 20313.2 Volcanically Active Bodies in the Solar System 20313.3 The Effects of Environmental Conditions on Volcanic Processes 20613.4 The Moon 20813.5 Mars 21213.6 Venus 21613.7 Mercury 21813.8 Io 22013.9 Europa 22213.10 Differentiated Asteroids 22313.11 Summary 22413.12 Further Reading 22413.13 Questions to Think About 224Answers to Questions 225Index 231