Introduction

As of June 2002, astronomers had discovered more than 100 other planets orbiting distant suns. With advances in technology, that number will surely increase during the opening decades of the twenty-first century. Although our explorations of the Cosmos hold great promise of future discoveries, among all of the known worlds, Earth remains unique. Thus far it is the only known planet with blue skies, warm seas, and life. Earth is our most tangible and insightful laboratory, and the study of Earth science offers us precious opportunities to discover many of the most fundamental laws of the Universe.

Although Earth is billions of years old, geology—literally meaning the study of Earth—is a relatively new science, having grown from seeds of natural science and natural history planted during the Enlightenment era of the eighteenth and nineteenth centuries. In 1807, the founding of the Geological Society of London, the first learned society devoted to geology, marked an important turning point for the science (some say its nascence). In the beginning, geologic studies were mainly confined to the study of minerals (mineralogy), strata (stratigraphy), and fossils (paleontology), and hotly debated issues of the day included how well new geologic findings fit into religious models of creation. In less than two centuries, geology has matured to embrace the most fundamental theories of physics and chemistry—and broadened in scope to include the diverse array of subdisciplines that comprise modern Earth science.

Modern geology includes studies in seismology (earthquake studies), volcanology, energy resources exploration and development, tectonics (structural and mountain building studies), hydrology and hydrogeology (water-resources studies), geologic mapping, economic geology (e.g., mining), paleontology (ancient life studies), soil science, historical geology and stratigraphy, geological archaeology, glaciology, modern and ancient climate and ocean studies, atmospheric sciences, planetary geology, engineering geology, and many other subfields. Although some scholars have traditionally attempted to compartmentalize geological sciences into subdisciplines, the modern trend is to incorporate a holistic view of broader Earth science issues. The incorporation of once-diverse fields adds strength and additional relevance to geoscience studies.

World of Earth Science is a collection of 650 entries on topics covering a diversity of geoscience related interests—from biographies of the pioneers of Earth science to explanations of the latest developments and advances in research. Despite the complexities of terminology and advanced knowledge of mathematics needed to fully explore some of the topics (e.g., seismology data interpretation), every effort has been made to set forth entries in everyday language and to provide accurate and generous explanations of the most important terms. The editors intend World of Earth Science for a wide range of readers. Accordingly, World of Earth Science articles are designed to instruct, challenge, and excite less experienced students, while providing a solid foundation and reference for more advanced students.

World of Earth Science has attempted to incorporate references and basic explanations of the latest findings and applications. Although certainly not a substitute for in-depth study of important topics, we hope to provide students and readers with the basic information and insights that will enable a greater understanding of the news and stimulate critical thinking regarding current events (e.g., the ongoing controversy over the storage of radioactive waste) that are relevant to the geosciences.

The broader and intellectually diverse concept of Earth science allows scientists to utilize concepts, techniques, and modes of thought developed for one area of the science, in the quest to solve problems in other areas. Further, many geological problems are interrelated and a full exploration of a particular phenomenon or problem demands overlap between subdisciplines. For this reason, many curricula in geological sciences at universities stress a broad geologic education to prepare graduates for the working world, where they may be called upon to solve many different sorts of problems.

World of Earth Science is devoted to capturing that sense of intellectual diversity. True to the modern concept of Earth science, we have deliberately attempted to include some of the most essential concepts to understanding Earth as a dynamic body traveling through space and time.

Although no encyclopedic guide to concepts, theories, discoveries, pioneers, issues and ethics related to Earth science could hope to do justice to any one of those disciplines in two volumes, we have attempted to put together a coherent collection of topics that will serve not only to ground students in the essential concepts, but also to spur interest in the many diverse areas of this increasing critical set of studies.

In addition to topics related to traditional geology and meteorology, we have attempted to include essential concepts in physics, chemistry, and astronomy. We have also attempted to include topical articles on the latest global positioning (GPS), measurement technologies, ethical, legal, and social issues and topics of interest to a wide audience. Lastly, we have attempted to integrate and relate topics to the intercom-plexities of economics and geopolitical issues.

Such a multifaceted and "real world" approach to the geosciences is increasingly in demand. In the recent past, geologic employment was dominated by the petroleum industry and related geologic service companies. In the modern world, this is no longer so. Mining and other economic geology occupations (e.g., prospecting and exploration), in former days plentiful, have also fallen away as major employers. Environmental geology, engineering geology, and ground water related jobs are more common employment opportunities today. As these fields are modern growth areas with vast potential, this trend will likely hold true well into the future. Many modern laws and regulations require that licensed, professional geologists supervise all or part of key tasks in certain areas of engineering geologic work and environmental work. It is common for professional geologists and professional engineers to work together on such projects, including construction site preparation, waste disposal, groundwater development, engineering planning, and highway construction. Many federal, state, and local agencies employ geologists, and there are geologists as researchers and teachers in most academic institutions of higher education.

Appropriate to the diversity of Earth science, we attempted to give special attention to the contributions by women and scientists of diverse ethnic and cultural backgrounds. In addition, we have included special articles written by respected experts that are specifically intended to make World of Earth Science more relevant to those with a general interest in the historical and/or geopolitical topics aspects of Earth science.

The demands of a dynamic science and the urgency of many questions related to topics such as pollution, global warming, and ozone depletion place heightened demands on both general and professional students of geosciences to increasingly broaden the scope and application of their knowledge.

For example, geological investigations of ancient and modern disasters and potential disasters are important—and often contentious—topics of research and debate among geologists today. Among the focus areas for these studies are earthquake seismicity studies. While much work continues in wellknown problem areas like southern California, Mexico City, and Japan, less well-known, but potentially equally dangerous earthquake zones like the one centered near New Madrid, Missouri (not far from Memphis, Tennessee and St. Louis, Missouri) now receive significnt research attention. Geologists cannot prevent earthquakes, but studies can help predict earthquake events and help in planning the design of earthquake-survivable structures. Another focus of study is upon Earth's volcanoes and how people may learn to live and work around them. Some volcanoes are so dangerous that no one should live near them, but others are more predictable. Earthquake prediction and planning for eruptions is going on today by looking at the geologic record of past eruptions and by modern volcano monitoring using thermal imaging and tilt or motion-measuring devices. Other foci of disaster prevention research include river-flood studies, studies of slope stability (prevention of mass movement landslides), seismic sea-wave (tsunami) studies, and studies of possible asteroid or comet impacts.

Aside from geologic studies of disaster, there is a side of geology centered upon providing for human day-to-day needs. Hydrology is an interdisciplinary field within geology that studies the relationship of water, the earth, and living things. A related area, hydrogeology, the study of ground water, has undergone a revolution recently in the use of computer modeling to help understand flow paths and characteristics. These studies of water flow on the surface and in the subsurface connect with other subdisciplines of geology, such as geomorphology (the study of landforms, many of which are formed by water flow), river hydrology, limnology (study of lakes), cave and sinkhole (karst) geology, geothermal energy, etc. Geologic studies related to human and animal health (i.e., medical geology) are becoming very common today. For example, much work is currently devoted to tracing sources of toxic elements like arsenic, radon, and mercury in rock, soil, air, water, and groundwater in many countries, including the United States. There has been a major effort on the part of medical geologists to track down dangerous mineral species of asbestos (not all asbestos is harmful) and determine how best to isolate or remove the material. Atmospheric scientists have been at work for some years on the issue of air-born pathogens, which ride across oceans and continents born on fine soil particles lifted by winds.

Geologists are also focused on study of the past. Today, paleobotany and palynology (study of fossil spores and pollen) complement traditional areas of invertebrate and vertebrate paleontogy. Recent discoveries such as small, feathered dinosaurs and snakes with short legs are helping fill in the ever-shrinking gaps within the fossil record of evolution of life on Earth. Paleontologic studies of extinction, combined with evidence of extraterrestrial bombardment, suggest that mass death and extinction of species on Earth at times in the past has come to us from the sky. In a slightly related area, geoarchaeology, the geologic context of archaeological remains and the geologic nature of archaeological artifacts remains key to interpreting details about the pre-historic human past. Careful study of drilling records of polar ice sheets, deep-sea sediments, and deep lake sediments has recently revealed that many factors, including subtle variations in some of Earth's orbital parameters (tilt, wobble, and shape of orbit around the Sun), has had a profound, cyclical effect upon Earth's climate in the past (and is continuing today). Paleontologic studies, combined with geologic investigations on temperature sensitive ratios of certain isotopes (e.g. O16/O18), have helped unlock mysteries of climate change on Earth (i.e., the greenhouse to icehouse vacillation through time).

Earth science studies are, for the first time, strongly focused on extraterrestrial objects as well. Voyages of modern exploratory spacecraft missions to the inner and outer planets have sent back a wealth of images and data from the eight major planets and many of their satellites. This has allowed a new field, planetary geology, to take root. The planetary geologist is engaged in photo-geologic interpretation of the origin of surface features and their chronology. Planetary geologic studies have revealed some important comparisons and contrasts with Earth. We know, for example, some events that affected our entire solar system, while the effects of other events were unique to certain planets and satellites. In addition, planetary geologists have found that impact-crater density is important for determining relative age on many planets and satellites. As a result, Earth is no longer the only planet with a knowable geologic time scale.

The geosciences have undergone recent revolutions in thought that have profoundly influenced and advanced human understanding of Earth. Akin to the fundamental and seminal concepts of cosmology and nucleosynthesis, beginning during the 1960s and continuing today, the concept of plate tectonics has revolutionized geologic thought and interpretation. Plate tectonics, the concept that the rigid outer part of Earth's crust is subdivided into plates, which move about on the surface (and have moved about on the surface for much of geologic time) has some profound implications for all of geology. This concept helps explain former mysteries about the distribution of volcanoes, earthquakes, and mountain chains. Plate tectonics also helps us understand the distribution of rocks and sediments on the sea floor, and the disparity in ages between continents and ocean floors. Plate motion, which has been documented through geologic time, helps paleontologists explain the distribution of many fossil species and characteristics of their ancient climates. Plate tectonic discoveries have caused a rewriting of historical geology textbooks in recent years.

Although other volumes are chartered to specifically explore ecology related issues, the topics included in World of Earth Science were selected to provide a solid geophysical foundation for ecological or biodiversity studies. We have specifically included a few revolutionary and controversial concepts, first written about in a comprehensive way during the 1970s, such as the Gaia hypothesis. Simply put, Gaia is the notion that all Earth systems are interrelated and interconnected so that a change in one system changes others. It also holds the view that Earth functions like a living thing. Gaia, which is really a common-sense philosophic approach to holistic Earth science, is at the heart of the modern environmental movement, of which geology plays a key part.

Because Earth is our only home, geoscience studies relating meteor impacts and mass extinction offer a profound insight into delicate balance and the tenuousness of life. As Carl Sagan wrote in Pale Blue Dot: A Vision of the Human Future in Space, "The Earth is a very small stage in a vast cosmic arena." For humans to play wisely upon that stage, to secure a future for the children who shall inherit Earth, we owe it to ourselves to become players of many parts, so that our repertoire of scientific knowledge enables us to use reason and intellect in our civic debates, and to understand the complex harmonies of Earth.

K. Lee Lerner & Brenda Wilmoth Lerner, editors
London
May, 2002

How to Use the Book

The articles in the book are meant to be understandable by anyone with a curiosity and willingness to explore topics in Earth science. Cross-references to related articles, definitions, and biographies in this collection are indicated by bold-faced type, and these cross-references will help explain, expand, and enrich the individual entries.

This first edition of World of Earth Science has been designed with ready reference in mind:

  • Entries are arranged alphabetically, rather than by chronology or scientific field.
  • Bold-faced terms direct reader to related entries.
  • "See also" references at the end of entries alert the reader to related entries not specifically mentioned in the body of the text.
  • A Sources Consulted section lists the most worthwhile print material and web sites we encountered in the compilation of this volume. It is there for the inspired reader who wants more information on the people and discoveries covered in this volume.
  • The Historical Chronology includes many of the significant events in the advancement of the diverse disciplines of Earth science. The most current entries date from just days before World of Earth Science went to press.
  • A comprehensive General Index guides the reader to topics and persons mentioned in the book. Bolded page references refer the reader to the term's full entry.

A detailed understanding of physics and chemistry is neither assumed nor required for World of Earth Science. In preparing this text, the editors have attempted to minimize the incorporation of mathematical formulas and to relate physics concepts in non-mathematical language. Accordingly, students and other readers should not be intimidated or deterred by chemical nomenclature. Where necessary, sufficient information regarding atomic or chemical structure is provided. If desired, more information can easily be obtained from any basic physics or chemistry textbook.

For those readers interested in more information regarding physics related topics, the editors recommend Gale's World of Physics as an accompanying reference. For those readers interested in a more comprehensive treatment of chemistry, the editors recommend Gale's World of Chemistry.

In an attempt to be responsive to advisor's requests and to conform to standard usage within the geoscience community, the editors elected to make an exception to previously used style guidelines regarding geologic time. We specifically adopted the convention to capitalize applicable eons, eras, periods and epochs. For example, Cenozoic Era, Tertiary Period, and Paleocene Epoch are intentionally capitalized.

Advisory Board

In compiling this edition, we have been fortunate in being able to rely upon the expertise and contributions of the following scholars who served as academic and contributing advisors for World of Earth Science, and to them we would like to express our sincere appreciation for their efforts to ensure that World of Earth Science contains the most accurate and timely information possible:

Cynthia V. Burek, Ph.D.
Environment Research Group, Biology Department
Chester College, England, U.K.

Nicholas Dittert, Ph.D.
Institut Universitaire Européen de la Mer
University of Western Brittany, France

William J. Engle. P.E.
Exxon-Mobil Oil Corporation (Rt.)
New Orleans, Louisiana

G. Thomas Farmer, Ph.D., R.G.
Earth & Environmental Sciences Division, Los Alamos National Laboratory
Los Alamos, New Mexico

Lyal Harris, Ph.D.
Tectonics Special Research Center, Dept. of Geology & Geophysics
University of Western Australia Perth, Australia

Alexander I. Ioffe, Ph.D.
Senior Scientist, Geological Institute of the Russian Academy of Sciences
Moscow, Russia

David T. King, Jr., Ph.D.
Professor, Dept. of Geology
Auburn University
Auburn, Alabama

Cherry Lewis, Ph.D.
Research Publicity Officer
University of Bristol
Bristol, England, U.K.

Eric v.d. Luft, Ph.D., M.L.S.
Curator of Historical Collections
S.U.N.Y. Upstate Medical University
Syracuse, New York

Jascha Polet, Ph.D.
Research Seismologist, Caltech Seismological Laboratory, California Institute of Technology
Pasadena, California

Yavor Shopov, Ph.D.
Professor of Geology & Geophysics
University of Sofia
Sofia, Bulgaria

Acknowledgments

In addition to our advisors and contributing advisors, it has been our privilege and honor to work with the following contributing writers and scientists who represent scholarship in the geosciences that spans five continents:

Molly Bell, Ph.D.; Alicia Cafferty; John Cubit, Ph.D.; Laurie Duncan, Ph.D.; John Engle; Agnes Galambosi; Larry Gilman, Ph.D.; David Goings, Ph.D.; Brooke Hall, Ph.D.; William Haneberg, Ph.D.; Michael Lambert; Adrienne Wilmoth Lerner, (Graduate Student, Department of History, Vanderbilt University), Lee Wilmoth Lerner, Jill Liske, M.Ed.; Robert Mahin, Ph.D.; Kelli Miller; William Phillips, Ph.D.; William Rizer, Ph.D.; Jerry Salvadore, Ph.D.; and David Tulloch, Ph.D.

Many of the academic advisors for World of Earth Science, along with others, authored specially commissioned articles within their field of expertise. The editors would like to specifically acknowledge the following special contributions:

Cynthia V. Burek, Ph.D.
History of geoscience: Women in the history of geoscience

Nicholas Dittert, Ph.D.
Scientific data management in Earth sciences

William J. Engle. P.E.
Petroleum, economic uses of Petroleum extraction

G. Thomas Farmer, Ph.D., R.G.
Hydrogeology

Lyal Harris, Ph.D.
Supercontinents

Alexander I. Ioffe, Ph.D.
Bathymetric mapping

David T. King, Jr., Ph.D.
Geologic time
Stratigraphy
Uniformitarianism

Cherry Lewis, Ph.D.
The biography of Author Holmes

Yavor Shopov, Ph.D.
Paleoclimate

The editors wish to gratefully acknowledge Dr. Eric v.d. Luft for his diligent and extensive research related to his compilation of selected biographies for World of Earth Science.

The editors also gratefully acknowledge Dr. Yavor Shopov's generous and significant contribution of photographs for World of Earth Science and Dr. David King's guidance, comments, and contributions to the introduction.

The editors thank Ms. Kelly Quin and others representing the Gale Imaging Team for their guidance through the complexities and difficulties related to graphics. Last, but certainly not least, the editors thank Mr. Ryan Thomason, whose dedication, energy, and enthusiasm made a substantial difference in the quality of World of Earth Science.

Because Earth is theirs to inherit, the editors lovingly dedicate this book to their children, Adrienne, Lee, Amanda, and Adeline. Per ardua ad astra.

Cover

The image on the cover depicts an example of several geologic cross sections of strata, illustrating the fundamental laws of geology.