CHAPTER 1 An Introduction to Geology
2
The Science
of Geology
The subject of this text is geology, from the
Greek geo, “Earth,” and logos, “discourse.” It
is the science that pursues an understanding of planet 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
(FIGURE 1.1). The aim of historical geology,
on the other hand, is to understand the origin of Earth and its development through
time. Thus, it strives to establish a 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. It should also
be pointed out that physical and historical
geology are divided into many areas of specialization. TABLE 1.1 provides a partial list.
TABLE 1.1
Different Areas of Geologic Study*
Archaeological Geology
Ocean Sciences
Biogeosciences
Paleoclimatology
Engineering Geology
Paleontology
Forensic Geology
Petrology
Geochemistry
Planetary Geology
Geomorphology
Sedimentary Geology
Geophysics
Seismology
History of Geology
Structural Geology
Hydrogeology
Tectonics
Medical Geology
Volcanology
Mineralogy
* Many of these areas of study represent interest sections and specialties of associated societies affiliated
with the Geological Society of America (www.geosociety.org) and the American Geophysical Union
(www.agu.org), two professional societies to which many geologists belong.
Every chapter of this book represents one
or more areas of specialization in geology.
To understand Earth is challenging
because our planet is a dynamic body with
many interacting parts and a complex history. Throughout
its long existence,
Earth has been
FIGURE 1.1 Rocks contain
information about the processes
that produce them. This large
exposure of igneous rock in
California’s Sierra Nevada
was once a molten mass
found deep within Earth.
Geologists study the
processes that create
and modify mountains
such as these. (Photo
by Brian Bailey/Aurora
Photos, Inc.)
changing. In fact, it is changing as you read
this page and will continue to do so into
the foreseeable future. Sometimes the
2
The Science
of Geology
The subject of this text is geology, from the
Greek geo, “Earth,” and logos, “discourse.” It
is the science that pursues an understanding of planet 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
(FIGURE 1.1). The aim of historical geology,
on the other hand, is to understand the origin of Earth and its development through
time. Thus, it strives to establish a 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. It should also
be pointed out that physical and historical
geology are divided into many areas of specialization. TABLE 1.1 provides a partial list.
TABLE 1.1
Different Areas of Geologic Study*
Archaeological Geology
Ocean Sciences
Biogeosciences
Paleoclimatology
Engineering Geology
Paleontology
Forensic Geology
Petrology
Geochemistry
Planetary Geology
Geomorphology
Sedimentary Geology
Geophysics
Seismology
History of Geology
Structural Geology
Hydrogeology
Tectonics
Medical Geology
Volcanology
Mineralogy
* Many of these areas of study represent interest sections and specialties of associated societies affiliated
with the Geological Society of America (www.geosociety.org) and the American Geophysical Union
(www.agu.org), two professional societies to which many geologists belong.
Every chapter of this book represents one
or more areas of specialization in geology.
To understand Earth is challenging
because our planet is a dynamic body with
many interacting parts and a complex history. Throughout
its long existence,
Earth has been
FIGURE 1.1 Rocks contain
information about the processes
that produce them. This large
exposure of igneous rock in
California’s Sierra Nevada
was once a molten mass
found deep within Earth.
Geologists study the
processes that create
and modify mountains
such as these. (Photo
by Brian Bailey/Aurora
Photos, Inc.)
changing. In fact, it is changing as you read
this page and will continue to do so into
the foreseeable future. Sometimes the