The Changing Earth: Exploring Geology and Evolution, 7th Edition

Book Preface

Earth is a dynamic planet that has changed continuously during its 4.6 billion years of existence. The size, shape, and geographic distribution of the continents and ocean basins have changed through time, as have the atmosphere and biota. As scientists and concerned citizens, we have become increasingly aware of how fragile our planet is and, more importantly, how interdependent all of its various systems and subsystems are.

We also have learned that we cannot continually pollute our environment and that our natural resources are limited and, in most cases, nonrenewable. Furthermore, we are coming to realize how central geology is to our everyday lives. For example, on March 11, 2011, a magnitude 9.0 earthquake struck Japan, killing more than 20,000 people and generating a tsunami that wreaked destruction along the coast of northeastern Japan, as well as damaging three nuclear power plants and causing radioactive leakage in one of them. A major oil spill in the Gulf of Mexico in 2010 resulted in much ecological damage along the shorelines of the Gulf Coast of the United States, as well as to the biota in the Gulf of Mexico. And, finally, Hurricane Sandy caused tremendous damage and major flooding along the Eastern Seaboard of the United States in October 2012. All of these events point out how much geology affects our lives, as well as the global economy. For these and other reasons, geology is one of the most important college or university courses that a student can take.

The seventh edition of The Changing Earth: Exploring Geology and Evolution is designed to be an introductory course in geology that can serve both majors and nonmajors in geology and the Earth sciences. One of the problems with any introductory science course is that students are overwhelmed by the amount of material that must be learned. Furthermore, most of the material does not seem to be linked by any unifying theme and does not always appear to be relevant to their lives. This book, however, is written to address that problem in that it shows, in its easy-to-read style, that geology is an exciting and ever-changing science in which new discoveries and insights are continually being made. The goals of this book are to provide students with a basic understanding of geology and its processes and, most importantly, with an understanding of how geology relates to the human experience—that is, how geology affects not only individuals, but society in general. It is also our intent to present the geologic and biologic history of Earth, not as a set of encyclopedic facts to memorize, but rather as a continuum of interrelated events reflecting the underlying geologic and biologic principles and processes that have shaped our planet and life upon it.

Instead of emphasizing individual, and seemingly unrelated, events, we seek to understand the underlying causes of why things happened the way they did and how all of Earth’s systems and subsystems are interrelated. Using this approach, students will gain a better understanding of how everything fits together, and why geology is such an important course. With these goals in mind, we introduce the major themes of the book in the first chapter to provide students with an overview of the subject and to enable them to see how the various systems, subsystems, and cycles of Earth are interrelated. We then cover the unifying theme of geology— plate tectonics—in the second chapter. Plate tectonic theory is central to the study of geology because it links together many aspects of geology. It is a theme that is woven throughout this edition.

The economic and environmental aspects of geology are emphasized throughout the book rather than treating these topics in separate chapters. In this way, students can see, through topical and interesting examples, how geology affects our lives. Climate change is an especially relevant and important topic that currently is in the news and being discussed and debated by scientists, politicians, and citizens alike. Because of its importance, we introduce the topic in the first chapter and integrate it throughout the book as it relates to the various topics covered. Geology is unique in that it can provide the perspective of geologic time in this important debate as to what, and the possible degree to which, humans have contributed to climate change. Another topic that has been in the news of late is hydraulic fracturing, popularly called “fracking.” This controversial method of releasing oil and gas from nearly impermeable shales, is both an environmental and energy issue that elicits strong feelings from both its proponents and opponents. Because of the importance of this topic and its cross-disciplinary nature, we cover it in several chapters

Brief Contents

1 Understanding Earth: A Dynamic and Evolving Planet 3
2 Plate Tectonics: A Unifying Theory 27
3 Minerals—The Building Blocks of Rocks 61
4 Igneous Rocks and Plutons 87
5 Volcanoes and Volcanism 111
6 Weathering, Erosion, and Soil 137
7 Sediment and Sedimentary Rocks 159
8 Metamorphism and Metamorphic Rocks 181
9 Earthquakes and Earth’s Interior 201
10 Deformation, Mountain Building, and Earth’s Crust 235
11 Mass Wasting 257
12 Running Water—Streams and Rivers 283
13 Groundwater 309
14 Glaciers and Glaciation 337
15 The Work of Wind and Deserts 363
16 Oceans, Shorelines, and Shoreline Processes 385
17 Geologic Time: Concepts and Principles 413
18 Organic Evolution—The Theory and Its Supporting Evidence 447
19 Precambrian Earth and Life History 471
20 Paleozoic Earth History 501
21 Paleozoic Life History 539
22 Mesozoic Earth and Life History 575
23 Cenozoic Earth and Life History 613
24 Geology in Perspective 655