Earth science is the name for all the sciences that collectively seek to understand Earth and its neighbors in space. It includes geology, oceanography, meteorology, and astronomy. Throughout its long existence, Earth has been changing. In fact, it is changing as you read this page and will continue to do so into the foreseeable future. Sometimes the changes are rapid and violent, such as when severe storms, landslides, and volcanic eruptions occur. Conversely, many changes take place so gradually that they go unnoticed during a lifetime. Scales of size and space also vary greatly among the phenomena studied in Earth science.

Earth science is often perceived as a science that is performed outdoors—and it is true that a great deal of an Earth scientist’s study is based on observations and experiments conducted in natural environments. But Earth science is also conducted in the laboratory, where, for example, the examination of various Earth materials provides insights into many of our planet’s basic processes and the creation of complex computer models allows for the simulation of our planet’s complicated climate system. Frequently, Earth scientists require an understanding of and must apply their knowledge about principles from physics, chemistry, and biology. Geology, oceanography, meteorology, and astronomy are sciences that seek to expand our knowledge of the natural world and our place in it.

Geology

The science of geology, a word that literally means “study of Earth.” Geology is traditionally divided into two broad areas: physical and historical.

Physical geology examines the materials composing Earth and seeks to understand the many processes that operate beneath and upon its surface. Earth is a dynamic, ever-changing planet. Under the surface, internal forces create earthquakes, build mountains, and produce volcanic structures ▼. At the surface, external processes break rock apart and sculpt a broad array of landforms. The erosional effects of water, wind, and ice result in a great diversity of landscapes. Because rocks and minerals form in response to Earth’s internal and external processes, their interpretation is basic to an understanding of our planet.

In contrast to physical geology, the aim of historical geology is to understand the origin of Earth and the development of the planet through its 4.6-billion-year history ▼. Historical geology strives to establish an orderly chronological arrangement of the multitude of physical and biological changes that have occurred in the geologic past. The study of physical geology logically precedes the study of Earth history because we must first understand how Earth works before we attempt to unravel its past.

Oceanography

Earth is often called the “water planet” or the “blue planet.” Such terms relate to the fact that more than 70 percent of Earth’s surface is covered by the global ocean. If we are to understand Earth, we must learn about its five primary ocean basins—the Pacific Ocean, the Atlantic Ocean, the Arctic Ocean, the Indian Ocean, and the Southern Ocean.

Oceanography is actually not a separate and distinct science. Rather, it involves the application of many sciences in a comprehensive and interrelated study of the oceans in all their aspects and relationships. Oceanography integrates chemistry, physics, geology, and biology. It includes the study of the composition and movements of seawater, as well as coastal processes, seafloor topography, and the characteristics and distribution of marine life.

Meteorology

Earth’s continents and oceans are surrounded by an atmosphere. The atmosphere is the mixture of gases that are held to the planet by gravity and thin rapidly with altitude. Acted on by the combined effects of Earth’s motions and energy from the Sun, and influenced by Earth’s land and sea surface, the formless and invisible atmosphere reacts by producing an infinite variety of weather, which in turn creates the basic pattern of global climates. Meteorology is the study of the atmosphere and the processes that produce weather and climate. Like oceanography, meteorology involves the application of other sciences in an integrated study of the thin layer of air that surrounds Earth.

Astronomy

Because Earth is related to all the other objects in space, the science of astronomy—the study of the universe—is very useful in probing the origins of our own environment. Because we are so closely acquainted with the planet on which we live, it is easy to forget that Earth is just a tiny object in a vast universe. Indeed, Earth is subject to the same physical laws that govern the many other objects populating the great expanses of space. Thus, to understand explanations of our planet’s origin, it is useful to learn something about the other members of our solar system. Moreover, it is helpful to view the solar system as a part of the great assemblage of stars that comprise our galaxy, which is but one of many galaxies.

Earth Science Is Environmental Science

Earth science is an environmental science that explores many important relationships between people and the natural environment. Many of the problems and issues addressed by Earth science are of practical value to people.

Natural Hazards

Natural hazards are a part of living on Earth. Every day they adversely affect literally millions of people worldwide and are responsible for staggering damages. Among the hazardous Earth processes studied by Earth scientists are volcanoes, floods, tsunamis, earthquakes, landslides, and hurricanes. Of course, these hazards are natural processes. They become hazards only when people live where these processes occur.

For most of history, most people lived in rural areas. However, today more people live in cities than in rural areas. This global trend toward urbanization concentrates millions of people into places that are vulnerable to natural hazards. Coastal sites are becoming increasingly vulnerable to wind and water hazards because development often destroys natural defenses, such as wetlands and sand dunes. In addition, there is a growing threat associated with human influences on the Earth system, such as sea level rise, which is linked to global warming and climate change. (The idea of Earth as a system is explored later in this chapter.) Other urban areas are exposed to seismic (earthquake) and volcanic hazards where inappropriate land use and poor construction practices, coupled with rapid population growth, increase vulnerability ▼.

Resources

Resources represent another important focus of Earth Science that is of great practical value to people. They include water and soil, a great variety of metallic and nonmetallic minerals, and energy. Together they form the very foundation of modern civilization. Earth Science deals with the formation, occurrence, and availability of vital resources and with the environmental impact of their extraction and use.

People Influence Earth Processes

Not only do Earth processes have an impact on people, but we humans can dramatically influence Earth processes as well. Human activities alter the composition of the atmosphere, triggering air pollution episodes and causing global climate change ▼. River flooding is natural, but the magnitude and frequency of flooding can be changed significantly as a result of human activities, such as clearing forests, building cities, and constructing dams. Unfortunately, natural systems do not always adjust to artificial changes in ways that we can anticipate. Thus, an alteration to the environment that was intended to benefit society often has the opposite effect.

Scales of Space and Time in Earth Science

When we study Earth, we must contend with a broad array of space and time scales ▼. Some phenomena are relatively easy for us to imagine, such as the size and duration of an afternoon thunderstorm or the dimensions of a sand dune. Other phenomena are so vast or so small that they are difficult to imagine. The number of stars and distances in our galaxy (and beyond!) or the internal arrangement of atoms in a mineral crystal are examples of such phenomena.

Some of the events we study occur in fractions of a second. Lightning is an example. Other processes extend over spans of tens or hundreds of millions of years. For example, the lofty Himalaya Mountains of Asia began forming nearly 50 million years ago, and they continue to develop today.

The concept of geologic time, the span of time since the formation of Earth, is new to many nonscientists. People are accustomed to dealing with increments of time that are measured in hours, days, weeks, and years. Our history books often examine events over spans of centuries, but even a century is difficult to appreciate fully.

Those who study Earth science must routinely deal with vast time periods—millions or billions (thousands of millions) of years. When viewed in the context of Earth’s 4.6-billion-year history, an event that occurred 100 million years ago may be characterized as “recent” by a geologist, and a rock sample that has been dated at 10 million years may be called “young.”

An appreciation for the magnitude of geologic time is important in the study of our planet because many processes are so gradual that vast spans of time are needed before significant changes occur. How long is 4.6 billion years? If you were to begin counting at the rate of one number per second and continued 24 hours a day, 7 days a week and never stopped, it would take about two lifetimes (150 years) to reach 4.6 billion!

The preceding analogy is just one of many that have been conceived in an attempt to convey the magnitude of geologic time. Although helpful, all of them, no matter how clever, only begin to help us comprehend the vast expanse of Earth history. The figure below ▼ provides another interesting way of viewing the vast amount of time represented by the age of Earth.

Over the past  years or so, Earth scientists have developed the geologic time scale of Earth history. It divides the  history of Earth into many different units and provides a meaningful time frame within which the events of the geologic past are arranged. 

• Earth science includes geology, oceanography, meteorology, and astronomy.

• There are two broad subdivisions of geology. Physical geology studies Earth materials and the internal and external processes that create and shape Earth’s landscape. Historical geology examines Earth’s history.

• The other Earth sciences seek to understand the oceans, the atmosphere’s weather and climate, and Earth’s place in the universe.

• Earth science is environmental science because it also is the study of the important interactions between humans and the environment.

• Earth science must deal with processes and phenomena that vary in size from the subatomic scale of matter to the nearly infinite scale of the universe.

• The time scales of phenomena studied in Earth science range from tiny fractions of a second to many billions of years.

• Geologic time, the span of time since the formation of Earth, is about 4.6 billion years, a number that is difficult to comprehend.

• astronomy: The scientific study of the universe, which includes the observation and interpretation of celestial bodies and phenomena.

• Earth science: The name for all the sciences that collectively seek to understand Earth. It includes geology, oceanography, meteorology, and astronomy.

• environmental science: The scientific study of the interactions of humans and Earth’s environment.

• geologic time: The span of time since the formation of Earth, about 4.6 billion years.

• geology: The science that examines Earth, its form and composition, and the changes it has undergone and is undergoing.

• meteorology: The scientific study of the atmosphere and atmospheric phenomena; the study of weather and climate.

• ocean basins: Deep submarine regions that lie beyond the continental margins.

• oceanography: The interdisciplinary scientific study of the oceans and oceanic phenomena.