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Physical Geology 101
1. Introduction to Geology
(p.1-6)
The textbook for this course is: Earth, An Introduction to Physical Geology (9th Ed.) by Tarbuck &
Lutgens. This course will follow the textbook closely so it will be a good resource to have. The
TurningPoint student response system (“clicker”) is also required for this course.
What is Geology?
Geology is a science: Greek "geo" = Earth, "logos" = discourse. So geology is the science of the Earth.
Age of the Earth
Geology is the study of the Earth and all its natural component parts that impact on each other. Although
we have no reason to believe that the processes we see happening around us today were any different to
the processes that have been occurring throughout Earth history, we know these processes are very slow,
which raises the issue about exactly how old the Earth is.
The earliest estimates of the age of the Earth were not based in science at all, but were determined from
biblical interpretations. James Ussher, an Irish Anglican archbishop, suggested in the early 17th century
that the Earth formed a mere 6010 years ago, in 4004 B.C.
Clearly, this estimate makes no sense scientifically as the geologic processes that constantly modify the
Earth are far too slow for anything of any consequence to happen in so short a time. Ussher’s supporters,
however, simply inferred that early geologic events (such as the creation of mountains) must have been
extremely rapid and catastrophic; an idea known as catastrophism.
However, there is no geologic evidence to support such an idea. With the advent of better scientific
studies and hypotheses, it became clear that the Earth is extremely ancient. This idea was first promoted
in the late 18th century by a Scottish physician named James Hutton, often referred to as the father of
modern geology. He coined the famous phrase regarding the age of the Earth: “no vestige of a beginning
– no prospect of an end.”
Hutton introduced the Principle of Uniformitarianism, which implies that we can study modern geologic
processes to understand the history of the Earth because of the great body of evidence that these modern
processes have occurred throughout Earth history. Simply stated, this principle advocates “the present is
the key to the past”.
In order to better understand the long complex history of our planet, we must develop a strong
understanding of its geologic complexity. This includes the evidence for how the Earth initially formed, its
internal structure, the material it is made out of, the nature of the Earth's surface and the natural
processes that operate at the surface, its dynamic characteristics such as earthquakes and volcanoes, its
resources, and its physical, chemical, and biological history.
Q: So what is Physical Geology?
Physical geology is concerned with the materials that make up the Earth as well as the processes that
operate on those materials, either at or beneath the surface of the Earth.
What materials?:
What processes?:
elements, minerals, rocks, water
plate tectonics, volcanic eruptions, earthquakes, mountain building, the action of
rivers, glaciers, oceans, and wind, and weathering and erosion.
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Physical Geology 101
To understand these processes and the great amounts of time needed to see their lasting impacts, we
have to think about time in a whole new way in comparison to human perceptions of time. In geology, we
have to think in terms of deep time, in which processes may occur over millions of years.
That’s why geologists developed the geologic time scale to divide the long duration of Earth history into
numerous time divisions, dating all the way back to about 4600 million years ago!
Course Information
The expectations and schedule are shown in the course syllabus and lecture plan.
Course website:
http://www.uidaho.edu/~simkat/geol101.html
What will we look at in this course?
 the origin of the Earth and how it has changed through time
 the composition of the Earth and its interior structure
 movements of tectonic plates and the causes of earthquakes and volcanoes
 the natural processes that shape the surface of the Earth
 the natural processes that modify the interior of the Earth
 Earth's resources that are utilized by mankind
 mankind's impact on the Earth and the environment
 the geology of other planets
 the development of life on Earth and implications for life on other planets
Why should we study geology?
We are fundamentally dependent on Earth's resources to function as a society.
We need to know where to find these resources so that society can continue to function. But, we must
also recognize that many of Earth's resources are finite and could eventually run out. So we must also
know how to manage our resources and recognize how our use of the resources may ultimately be
impacting on the planet.
We also need to know about geology for practical reasons, like choosing a safe place to construct
buildings where they will be safe from river flooding, landslides, earthquakes, volcanic eruptions, and other
potential natural disasters. We also need to be able to pick safe sites for building dams and bridges,
nuclear power stations, and for disposing of society's waste products so as not to create environmental
disasters.
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