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Guide
to Reading 
Rocks are the natural energy resources for the essentials
of modern life: electricity and fuel. The types of resources vary;
this chapter presents an overview of several. Since you’ve
had eleven chapters’ worth of geology background, it’s
assumed you already know the basic rock types, geologic structures,
geologic time, and Earth history. Therefore this chapter needs to
introduce few new concepts, but there are many new vocabulary words
and a resulting long list of terms to be familiar with.
Your author begins with the energy resource modern
society relies on most: fossil fuels (petroleum, natural gas, and
coal). Foremost among these is petroleum (oil). To understand its
diverse makeup, you learn some basic organic chemistry and the significance
of the molecular size of hydrocarbons.
How does petroleum form and accumulate? You read
about plankton; source rock and reservoir rock; oil reserves, traps,
and seals; and the relationship between natural gas and oil.
How do you find petroleum, get it out of the ground,
and process it? Topics include seismic search methods, drilling wells
(drill bits, drilling mud, and gushers), and what happens to crude
oil in the distillation column of a refinery.
A little history of the petroleum industry in the
United States is included in this section. It’s colorful stuff,
ranging from patent medicines of pioneer days to the bogus “Colonel”
Edwin Drake and his oil well at Titusville, Pennsylvania.
Coal is another fossil fuel and the next-most-used
energy resource. You read of its formation from swamp plant material
and its sequence of development (peat, lignite, bituminous coal,
and anthracite coal). How much does the world depend on coal for
energy, can this situation change, and how wise is it to become more
dependent on yet another fossil fuel? Topics included are economic
coal seams, coal reserves, strip mining versus underground mining,
the hazards of coal mining, and the potential environmental impact.
A few decades ago, when the world started to become
concerned about the future availability of fossil fuels, nuclear
power seemed to many people to be the answer. What happened that
it hasn’t become the world’s chief energy source? You
start with learning the difference between fission and fusion and
which one is used in nuclear power plants. What are pitchblende,
nuclear reactors, fuel rods, control rods, and chain reactions? Just
how dangerous is nuclear energy? You read about critical mass and
possible explosion, and the concerns over what to do with nuclear
wastes.
The next part of the chapter is based on an opinion
held by most experts in both science and industry: We have been living
in a unique and very limited time in human history, the Oil Age.
We are quickly running out of commercial quantities of oil and the
end is in sight. Even though oil (and coal, too) are forming in today’s
world, this happens so slowly that from the human viewpoint they
are nonrenewable resources. Your author gives you figures of current
oil consumption, oil reserves, scientific estimates of when we’ll
run out, and what our options are as that time approaches. There
are basically two options: give up and accept a lower standard of
living, or switch to alternative energy resources.
Several of these alternative energy Earth resources
are already being used, but not extensively. You read about geothermal
energy, hydroelectric power, tar sands, oil shale, and solar energy.
There seems to be no perfect answer; each energy
option has advantages and disadvantages in terms of efficiency, cost,
political consequences, and environmental impact. But it does seem
as though some choices must be made and some steps taken soon so
that the Arabian saying doesn’t become reality: “My father
rode a camel. I drive a car. My son rides in a jet airplane. His
son will ride a camel.”
In addition to being an energy resource, rocks give
us the raw materials for our very comfortable lifestyles in our industrial
society. The chapter continues with discussion of these nonenergy
geologic resources. It talks about the geologic reasons for their
existence, methods of extracting them from the Earth, products made
from them, concerns about future supplies, and the environmental
impact caused by their extraction.
The raw materials are both metallic and nonmetallic
mineral resources. Some are not only useful to humankind but are
highly prized by society. The native metal, gold, influenced the
course of history worldwide. The author discusses gold and many more
mundane metals (including copper, tin, iron, aluminum, lead, zinc,
and manganese). Topics of discussion are these:
- What are metallic characteristics and how do you
work with metals? You read about metallic bonds, smelting, slag,
and alloys like steel.
- How do you extract metals from the Earth? You
read about underground mining, open pit mines, ores, ore minerals,
grade of an ore, shows, assays, and adits.
- How can you classify ore deposits? On the basis
of their origins: magmatic (including massive-sulfide deposits),
hydrothermal (including disseminated, vein and porphyry deposits,
and black smokers), secondary-enrichment deposits (including banded-iron
formations and manganese nodules), residual mineral deposits (what’s
left after leaching by groundwater), and placer deposits (of dense
materials).
- Where do you look for ore deposits? Metallic minerals
aren’t evenly distributed worldwide. Why are deposits found
in some places and not in others? Plate tectonics, of course! You
get details of ores from the Andes of Peru and Chile to the ocean
bottom. You’ve gotten so used to plate tectonics being the
reason for everything, you may be surprised to learn plate tectonics
had no direct bearing on the formation of banded-iron formations
(BIFs) or on residual ore deposits like bauxite.
In all those discussions of metals, and throughout
the rest of the chapter, the author has had to make choices of what
examples he’ll use. While it’s never a bad idea to learn
as much detail as is reasonable, it’s most important for you
to understand the concepts being explained by use of the examples.
Your teacher may use local examples of minerals to illustrate concepts.
Nonmetallic mineral resources don’t have the
glamour of gold, but they’ve been equally useful to humankind.
Centuries ago people began to quarry stone to construct impressive
and enduring buildings, and as time has passed, society has continued
to use building stone and numerous other nonmetallic resources. The
chapter mentions many of these resources and products made from them,
including cement, concrete, gravestones, flagstones, bricks, crushed
rock, window glass, asbestos, landscaping rock, salt, and gypsum.
As this chapter has already pointed out, society
has become very concerned about the diminishing amounts of energy
reserves; it is also starting to be concerned about diminishing amounts
of mineral reserves. As with energy resources, mineral resources
are nonrenewable and unevenly distributed around the world. This
causes economics and politics to play important roles in any scenario
that concerns mineral reserves. How long a resource lasts depends
in part on how badly people want it and what they’re willing
to pay for it. Many of these materials have been fought over in the
past; the United States stockpiles some of its strategic metals in
the hope of avoiding battles in the future.
The chapter ends with a sensitive topic, mining
and the environment. Even if things run smoothly in the political
sense, extracting minerals on a large scale can be costly to the
environmental quality on Earth. We want all the good things of life
Earth can supply. Balancing our material desires with minimal environmental
impact is becoming a growing challenge.
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