Geology Reference
In-Depth Information
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Buried deep in the earth are the remnants of earlier life forms—hundreds of millen-
nia of rotting vegetation, decaying animals, and marine plankton. Today this “or-
ganic material” (so-called because it was once alive) has turned into rock that is
laden with carbon, which can be burned for fuel. “Fossil fuels,” such as coal, oil,
and natural gas, were formed some 286 to 360 million years ago in the Carbonifer-
ous period, which predated the dinosaurs and is part of the Paleozoic Era.
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The word “carboniferous” is rooted in carbon, the basis of fossil fuels. During
the Carboniferous period the earth was populated by trees, large leafy plants, and
ferns, and its water bodies were rich with algae, a common phytoplankton. As these
plants and animals died, they sank to the bottom of the swamps and oceans, form-
ing layers of spongy earth called peat. Over millions of years, silt, sand, and clay
covered the peat; as the layers of minerals built up, the peat was compressed until
the water had been completely squeezed out of it. Eventually, the organic material
was buried deeper and deeper and turned into rock. Increasing heat and geologic
pressure transformed some of the rock into fossil fuels. Today, man drills deeply
into the earth to reach the geologic formations in which coal, oil, and natural gas
are trapped.
Unlike “renewable” wind or solar power, fossil fuels are “nonrenewable,” or fi-
nite, energy supplies: once they are used, they are gone for good; their excavation
and burning creates pollution, including greenhouse gases such as carbon dioxide
(CO
2
). Nevertheless, fossil fuels remain our primary source of energy.
That wasn't always the case. Until the late eighteenth century, the United States
was an agrarian society, in which wind and water provided much of the power used
to mill flour, saw wood, or irrigate crops. Burning wood or peat provided heat to
