ix
• Igneous Textures: What Can They Tell Us? 67
Factors Affecting Crystal Size 67
Types of Igneous Textures 68
• Naming Igneous Rocks 71
Felsic (Granitic) Igneous Rocks 71
Intermediate (Andesitic) Igneous Rocks 74
Mafic (Basaltic) Igneous Rocks 74
Pyroclastic Rocks 75
Origin of Magma 76
Generating Magma from Solid Rock 76
How Magmas Evolve 77
Bowen’ s Reaction Series and the Composition
of Igneous Rocks 78
Assimilation and Magma Mixing 79
Partial Melting and Magma Composition 80
• Intrusive Igneous Activity 80
Nature of Intrusive Bodies 81
Tablular Intrusive Bodies: Dikes and Sills 82
Massive Intrusive Bodies: Batholiths, Stocks, and
Laccoliths 83
Mineral Resources and Igneous Processes 84
THE CHAPTER IN REVIEW 88 KEY TERMS 88
GIVE IT SOME THOUGHT 88 COMPANION
WEBSITE 89
4 Volcanoes
and Volcanic Hazards 90
Mount St. Helens Versus Kilauea 92
• The Nature of Volcanic Eruptions 93
Factors Affecting Viscosity 93
Why Do Volcanoes Erupt? 94
• Materials Extruded during an Eruption 95
Lava Flows 95
Gases 96
Pyroclastic Materials 98
• Volcanic Structures and Eruptive Styles 99
Anatomy of a Volcano 99
Shield Volcanoes 100
Cinder Cones 102
Composite Cones 104
Living in the Shadow of a Composite Cone 105
Nuée Ardente: A Deadly Pyroclastic Flow 105
Lahars: Mudflows on Active and Inactive Cones 108
Other Volcanic Landforms 108
Calderas 108
Fissure Eruptions and Basalt Plateaus 110
Lava Domes 111
Volcanic Pipes and Necks 112
Plate Tectonics and Volcanic Activity 113
Volcanism at Convergent Plate Boundaries 116
Volcanism at Divergent Plate Boundaries 116
Intraplate Volcanism 117
Living with Volcanoes 118
Volcanic Hazards 118
Monitoring Volcanic Activity 119
THE CHAPTER IN REVIEW 120
KEY TERMS 120 GIVE IT SOME THOUGHT 121
COMPANION WEBSITE 121
5 Weathering and Soils 122
• Earth’s External Processes 124
• Weathering 125
• Mechanical Weathering 125
Frost Wedging 126
Salt Crystal Growth 126
Sheeting 127
Biological Activity 128
• Chemical Weathering 128
Water and Carbonic Acid 128
How Granite Weathers 129
Weathering of Silicate Minerals 130
Spheroidal Weathering 130
• Rates of Weathering 131
Rock Characteristics 131
Climate 132
Differential Weathering 132
Soil 133
An Interface in the Earth System 133
What Is Soil? 133
Controls of Soil Formation 133
Parent Material 133
Time 135
Climate 136
• Igneous Textures: What Can They Tell Us? 67
Factors Affecting Crystal Size 67
Types of Igneous Textures 68
• Naming Igneous Rocks 71
Felsic (Granitic) Igneous Rocks 71
Intermediate (Andesitic) Igneous Rocks 74
Mafic (Basaltic) Igneous Rocks 74
Pyroclastic Rocks 75
Origin of Magma 76
Generating Magma from Solid Rock 76
How Magmas Evolve 77
Bowen’ s Reaction Series and the Composition
of Igneous Rocks 78
Assimilation and Magma Mixing 79
Partial Melting and Magma Composition 80
• Intrusive Igneous Activity 80
Nature of Intrusive Bodies 81
Tablular Intrusive Bodies: Dikes and Sills 82
Massive Intrusive Bodies: Batholiths, Stocks, and
Laccoliths 83
Mineral Resources and Igneous Processes 84
THE CHAPTER IN REVIEW 88 KEY TERMS 88
GIVE IT SOME THOUGHT 88 COMPANION
WEBSITE 89
4 Volcanoes
and Volcanic Hazards 90
Mount St. Helens Versus Kilauea 92
• The Nature of Volcanic Eruptions 93
Factors Affecting Viscosity 93
Why Do Volcanoes Erupt? 94
• Materials Extruded during an Eruption 95
Lava Flows 95
Gases 96
Pyroclastic Materials 98
• Volcanic Structures and Eruptive Styles 99
Anatomy of a Volcano 99
Shield Volcanoes 100
Cinder Cones 102
Composite Cones 104
Living in the Shadow of a Composite Cone 105
Nuée Ardente: A Deadly Pyroclastic Flow 105
Lahars: Mudflows on Active and Inactive Cones 108
Other Volcanic Landforms 108
Calderas 108
Fissure Eruptions and Basalt Plateaus 110
Lava Domes 111
Volcanic Pipes and Necks 112
Plate Tectonics and Volcanic Activity 113
Volcanism at Convergent Plate Boundaries 116
Volcanism at Divergent Plate Boundaries 116
Intraplate Volcanism 117
Living with Volcanoes 118
Volcanic Hazards 118
Monitoring Volcanic Activity 119
THE CHAPTER IN REVIEW 120
KEY TERMS 120 GIVE IT SOME THOUGHT 121
COMPANION WEBSITE 121
5 Weathering and Soils 122
• Earth’s External Processes 124
• Weathering 125
• Mechanical Weathering 125
Frost Wedging 126
Salt Crystal Growth 126
Sheeting 127
Biological Activity 128
• Chemical Weathering 128
Water and Carbonic Acid 128
How Granite Weathers 129
Weathering of Silicate Minerals 130
Spheroidal Weathering 130
• Rates of Weathering 131
Rock Characteristics 131
Climate 132
Differential Weathering 132
Soil 133
An Interface in the Earth System 133
What Is Soil? 133
Controls of Soil Formation 133
Parent Material 133
Time 135
Climate 136