Laboratory Manual for Introductory Geology 4e

CHAPTER 4
Minerals, Rocks, and the
Rock Cycle................................................. 89
4.1 Introduction 90
4.2 The Three Classes of Rocks 90
4.2.1 The Rock Cycle 91
4.3 A Rock Is More than the Sum of Its Minerals 91
4.3.1 Describing Texture 91
4.4 The Processes That Produce Textures 96
4.5 Clues about a Rock’s Origin from the
Minerals It Contains 100
4.6 Identifying Minerals in Rocks 100
4.7 Interpreting the Origin of Rocks 103
4.8 The Economic Value of Rocks 106
CHAPTER 5
Using Igneous Rocks to Interpret
Earth History.............................................111
5.1 Introduction 112
5.2 Interpreting the Cooling Histories
of Igneous Rocks 113
5.2.1 Grain Size in Crystalline Igneous Rock 114
5.2.2 Glassy Igneous Textures 118
5.2.3 Porous (Vesicular) Textures 118
5.2.4 Fragmental Textures 118
5.2.5 Grain Shape 120
5.3 Igneous Rock Classification and
Identification 121
5.3.1 Igneous Rock Classification: The Four Major
Compositional Groups 121
5.3.2 Identifying Igneous Rocks 122
5.4 Origin and Evolution of Magmas 123
5.4.1 Where and Why Do Rocks and Minerals
Melt? 124
5.4.2 How Do Rocks and Minerals Melt? 124
5.4.3 Factors Controlling Magma Composition 127
5.5 Igneous Rocks and Plate Tectonics 129
5.5.1 Plate-Tectonic Settings of Ultramafic Rocks
(Peridotite) 129
5.5.2 Plate-Tectonic Settings of Mafic Igneous Rocks
(Basalt and Gabbro) 130
5.5.3 Plate-Tectonic Settings of Intermediate Igneous
Rocks (Andesite and Diorite) 130
5.5.4 Plate-Tectonic Settings of Felsic Rocks (Granite
and Rhyolite) 131
5.6 Volcanoes and Volcanic Hazards 132
5.6.1 Volcanic Landforms 132
5.6.2 Living with Volcanoes 134
CHAPTER 6
Using Sedimentary Rocks to
Interpret Earth History....................... 143
6.1 Introduction 144
6.2 Sediment Formation and Evolution 144
6.2.1 The Origin of Sediment 144
6.2.2 Weathering and Its Influence on Sediment
Composition 144
6.2.3 Mineralogical Maturity 145
6.3 The Basic Classes of Sedimentary Rocks 147
6.3.1 Clastic Sedimentary Rocks 147
6.3.2 Chemical Sedimentary Rocks 150
6.3.3 Biochemical and Organic Sedimentary Rocks 152
6.4 Identifying Sedimentary Rocks 153
6.5 Interpreting Clastic Sedimentary Textures 157
6.5.1 Grain Size and Sorting 157
6.5.2 Grain Shape 159
6.5.3 Sediment “Maturity” 159
6.5.4 Cements in Clastic Rocks 161
6.6 Sedimentary Structures: Clues to Ancient
Environments 161
6.6.1 Beds and Stratification 161
6.6.2 Sedimentary Structures 161
6.7 Fossils: Remnants of Past Life 165
6.8 Applying Your Knowledge to Stratigraphy 165
CHAPTER 7
Interpreting Metamorphic Rocks.....173
7.1 Introduction 174
7.2 What Changes during Metamorphism? 174
7.2.1 Changes in Texture 174
7.2.2 Changes in Mineralogy 175
7.2.3 Changes in Composition 175
7.3 Agents of Metamorphism 175
7.3.1 The Effect of Heat 175
7.3.2 The Effect of Pressure 177
7.3.3 The Effects of Stress 180
7.3.4 The Effect of Hydrothermal Fluids 180
7.4 Studying Metamorphic Rocks 180
7.4.1 How to Determine if a Rock Is Metamorphic 181
7.4.2 Metamorphic Rock Classification and
Identification 182
7.4.3 Descriptions of Common Metamorphic Rocks 182
7.5 What Can We Learn from a Metamorphic
Rock? 186
7.5.1 Identifying the Protolith 187
7.5.2 Interpreting the Type of Metamorphism and
Geologic Setting 188
7.5.3 Estimating the Grade of Metamorphism 190
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CONTENTS