Earth Science

GEOLOGIC TIME

CONCEPT The expression geologic time refers to the vast span from Earth’s beginnings to the present, about 4.6 billion years. To examine the history of Earth, one must discard most familiar ideas about time. Instead of thinking in terms of years, centuries, or even millennia, the most basic unit is a million years, and even […]

HISTORICAL GEOLOGY

CONCEPT Geologists are concerned primarily with two subjects: Earth’s physical features and the study of the planet’s history. These two principal branches of geology are known, appropriately enough, as physical geology and historical geology. Today they are of equal importance, but in the early modern era, geologists were most focused on topics related to historical […]

SUN, MOON, AND EARTH

CONCEPT Earth is intimately tied to the star around which it revolves, the Sun, and the satellite that revolves around Earth itself, the Moon. Without the Sun, of course, life on Earth simply could not exist, not just because of the need for light but to an even greater degree because of the energy it […]

PLANETARY SCIENCE

CONCEPT The term planetary science encompasses a whole range of studies involving a combination of earth sciences and astronomy. Sometimes known as planetology or planetary studies, these disciplines are concerned primarily with the geologic, geophysical, and geochemical properties of other planets. They also draw on areas of astronomy, such as cosmology,a fascinating discipline devoted to […]

REMOTE SENSING

CONCEPT Scientists of many disciplines are accustomed to studying data that cannot be observed through direct contact. Physicists and chemists, for instance, know a great deal about the structure of the atom, even though even the most high-powered microscope cannot make an atom visible to the human eye. The objects of study for earth scientists […]

MEASURING AND MAPPING EARTH

CONCEPT Today a sharp distinction exists between the earth sciences and geography, but this has not always been the case. In ancient times, when scientists lacked the theoretical or technological means to study Earth’s interior, the two disciplines were linked much more closely. Even in the centuries since these disciplines parted ways, the earth sciences […]

STUDYING EARTH

CONCEPT The physical sciences include astronomy, physics, chemistry, and the earth sciences, but the last of these sciences is quite unlike the other three. Whereas the objects of study in physics and chemistry often seem abstract to the uninitiated and astronomy is concerned with faraway planets and other bodies, the earth sciences are devoted to […]

EARTH SYSTEMS

CONCEPT A system is any set of interactions set apart from the rest of the universe for the purposes of study, observation, and measurement. Theoretically, a system is isolated from its environment, but this is an artificial construct, since nothing is ever fully isolated. Earth is largely a closed system, meaning that it exchanges very […]

GEOSCIENCE AND EVERYDAY LIFE

CONCEPT How can learning about rocks help us in our daily lives? The short answer is that geology and the related geologic sciences (sometimes referred to collectively as geoscience) give us a glimpse of the great complexity inherent in the natural world, helping us appreciate the beauty and order of things. This, in turn, makes […]

EARTH, SCIENCE, AND NONSCIENCE

CONCEPT To understand the composition and structure of Earth, one must comprehend the forces that shaped it. Much the same is true of the earth sciences themselves, which originated from attempts to explain the origins of Earth and the materials of which it is composed. Before the modern era, such explanations had roots in religion, […]

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