Introduction
Geology is the study of the earth. By default this means that geology is a vast, complex, and intricate topic. But “vast, intricate, and complex” does not necessarily mean difficult. Many folks interested in geology just don’t know where to start. Minerals? Rocks? Glaciers? Volcanoes? Fossils? Earthquakes? The sheer number of topics covered under the heading “geology” can be overwhelming.
Enter Geology For Dummies! The goal of this book is to break through the overwhelming array of geology information and provide a quick reference for key concepts in the study of the earth.
My hope is that you find this book both interesting and useful, whether you’ve purchased it to accompany a course you’re taking in school or to help you find answers to questions you have about the planet you live on.
About This Book
In Geology For Dummies, you can start anywhere. This book is written as an introduction to the most common topics in geology. Follow your interest from one topic to the next, or start at the beginning and read the chapters in order. I wrote the book in a style that allows you to open to any page and learn something. But if you want to start at the beginning, you’re introduced to the concepts in a logical and structured order that (I hope!) answers your questions almost as soon as you ask them.
Throughout the book you find cross-references to other chapters. I use them because it’s impossible to explore one topic in geology without touching on many others. The multiple cross-references weave together the different parts of geologic study into a complex whole.
Wherever possible, I include illustrations to accompany my explanations. Geology is all around you, so while you are busy reading this book and examining the illustrations, I encourage you to also look around and find real-world examples of the processes and features I describe. To this end, I have also included a color photo section in the middle of the book featuring vivid images that help bring the subject matter to life.
Conventions Used in This Book
Throughout this book you find measurements expressed in both metric and English units. Scientists around the world use metric units as their standard, but in the United States and England it is still common to use measures of inches, feet, and miles, so I include both.
As with any science, geology has its own jargon, which you need to know in order to understand key concepts. Whenever I introduce a word I suspect you may not know, I put that word in italic and provide a definition nearby.
What You’re Not to Read
Throughout this book you find sidebars highlighted in gray. Feel free to skip these, as they are not integral to the information presented in each chapter. The sidebars include extra information, or particularly interesting tidbits that I thought you might enjoy.
Similarly, any paragraph with the Technical Stuff icon beside it explains or describes a concept in extra detail, beyond what you need to have a basic grasp of the idea. Feel free to skip these paragraphs or breeze through them if you’re looking only for the basics.
Foolish Assumptions
As I was writing this book, I had to make a few assumptions about you, the reader. I assume that you live on earth and are familiar with rocks, streams, and weather (rain, wind, and sun). I also assume that you are familiar with a very basic geography of the earth, including the continents, oceans, and major mountain ranges.
I do not assume that you have any scientific background in chemistry, which you may find useful if you want to dig deeper into the details of rock formation and transformation. Similarly, when I discuss evolution I do not assume that you have any background in biology or anatomy (and none is needed to understand the concepts I present). If the subject of evolution interests you, you may find that your questions lead you to pick up other reference books on that topic.
If you find that your interest in geology is further fueled by this book, I recommend that you purchase an earth science or geology dictionary. Geology is full of terms with precise and informative meanings. With this kind of dictionary on hand, you’ll find you can easily interpret even the most befuddling geological explanations.
How This Book Is Organized
This book is organized into multiple parts that group topics together logically. Here, I briefly describe what you find in each part of Geology For Dummies.
Part I: Studying the Earth
In Part I you are introduced to science in general and geologic or earth science in particular. This part begins with an overview of the scientific approach and how you use it in everyday life. It also covers the differences among hypotheses, theories, laws, and paradigms.
A brief history of geologic thought and the development of modern ideas about the earth are covered in Chapter 3. In this chapter I also include a description of some of modern geology’s cutting edge research topics, such as Snowball Earth and mass extinctions.
In Chapter 4, I describe the multiple layers of the earth and how scientists have determined what the interior of the earth looks like when they cannot actually observe it.
Part II: Elements, Minerals, and Rocks
The building blocks of earth are the elements, minerals, and rocks that I describe in Part II. First I cover some chemistry basics about how atoms bond together to form minerals, and how minerals combine to form rocks. Chapter 7 describes the different rock types common on earth, as well as how and where they are formed.
Part III: One Theory to Explain It All: Plate Tectonics
The theory of plate tectonics is the unifying theory of geology. It draws together in a single explanation how the interaction of plate movements forms, destroys, and recycles rocks. In Part III I explain how geologists took many decades to transform the plate tectonics hypothesis into a theory of plate tectonics. I also explain the different types of crustal rock that cover the earth and how continental plates create different features as they crash together or rip apart. In the last chapter of this part, I describe the three dominant theories for what drives the constant motion of crustal plates.
Part IV: Superficially Speaking: About Surface Processes
Part IV breaks down surface processes of geology into five main categories. I explain forces of gravity, flowing water, ice, wind, and waves and how they shape the surface of earth by moving rocks and sediments.
Part V: Long, Long Ago in This Galaxy Right Here
Part V provides a very brief introduction to historical geology. I begin by explaining how geologists determine the age of rocks using relative and absolute dating techniques. That is followed by an introduction to the geologic timescale, a segmented sequence of more than 4.5 billion years. In this part you also find descriptions of the major geologic and evolutionary events in each of earth’s major time periods, beginning with the Precambrian and including the Paleozoic, Mesozoic, and Cenozoic.
Part VI: The Part of Tens
The final part of this book provides you with two lists. The first is a list of ten ways humans act as geologic agents, shaping or restructuring the surface of the earth. The second is a list of the most common (and a few not-so-common) geologic hazards, such as landslides, earthquakes, and tsunamis.
Icons Used in This Book
Throughout this book, I use icons to draw your attention to certain information.
Where to Go from Here
You have most likely purchased this book with a question about geology already in mind. In that case, I encourage you to follow your interest. Use the table of contents or index to find where I answer your question, flip to that page, and get started!
If you don’t have a particular question in mind, here are a few of my favorite topics that will get you started on your study of earth:
Chapter 8, “Adding Up the Evidence for Plate Tectonics”: In this chapter I tell you the story of how an early geologist, Alfred Wegener, began to think about plate movements. He collected evidence to support his ideas, but it took many years before the idea of plate tectonics was accepted by the scientific community. This chapter is a great introduction to how science really happens, as well as an overview of the foundational theory of modern geology.
Chapter 12, “Water: Above and Below Ground”: If you want to get started by reading about something you can relate to, start with flowing water. Streams and rivers are the most common geologic processes on earth. Regardless of where you live, you have probably witnessed the action of flowing water moving sediment or rocks. This chapter provides details from how water picks up and carries particles, to how rivers carve canyons and caves. It also covers the topic of groundwater, which is where most of the water you drink comes from.
Chapter 18, “Time before Time Began: The Precambrian”: Long ago in earth’s deep, dark, murky past lay the beginnings of life. This chapter describes the first few billion years of earth’s existence, from its formation from a gaseous cloud, up to and including the earliest evidence for life — in the form of trace fossils called stromatolites.