Geology Reference
In-Depth Information
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development among all the world's nations. Geologists will
continue to play an important role in meeting these demands
by locating the needed resources and ensuring protection of
the environment for the benefi t of future generations.
What Would You Do
An important environmental issue facing the world today is
global warming. How can this problem be approached from
a global systems perspective? What are the possible con-
sequences of global warming, and can we really do anything
about it? Are there ways to tell whether global warming oc-
curred in the geologic past?
GLOBAL GEOLOGIC AND
ENVIRONMENTAL ISSUES
FACING HUMANKIND
Most scientists would argue that overpopulation is the
greatest environmental problem facing the world today. The
world's population reached 6.7 billion in 2007, and projec-
tions indicate that this number will grow by at least another
billion people during the next two decades, bringing Earth's
human population to more than 7.7 billion. Although this
may not seem to be a geologic problem, remember that
these people must be fed, housed, and clothed, and all with
a minimal impact on the environment. Much of this popu-
lation growth will be in areas that are already at risk from
such hazards as earthquakes, tsunami, volcanic eruptions,
and floods. Adequate water supplies must be found and
protected from pollution. Additional energy resources will
be needed to help fuel the economies of nations with ever-
increasing populations. New techniques must be developed
to reduce the use of our dwindling nonrenewable resource
base and to increase our recycling efforts so that we can de-
crease our dependence on new sources of these materials.
The problems of overpopulation and how it affects the
global ecosystem vary from country to country. For many poor
and non-industrialized countries, the problem is too many
people and not enough food. For the more developed and in-
dustrialized countries, it is too many people rapidly depleting
both the nonrenewable and renewable natural resource base.
And in the most industrially developed countries, it is people
producing more pollutants than the environment can safely
recycle on a human timescale. The common thread tying these
varied situations together is an environmental imbalance
created by a human population exceeding Earth's short-term
carrying capacity.
An excellent example of how Earth's various subsystems
are interrelated is the relationship between the greenhouse ef-
fect and global warming (see Geo-Focus on pages 10 and 11).
As a by-product of respiration and the burning of organic ma-
terial, carbon dioxide is a component of the global ecosystem
and is constantly being recycled as part of the carbon cycle. The
concern in recent years over the increase in atmospheric car-
bon dioxide levels is related to its role in the greenhouse effect.
The recycling of carbon dioxide between Earth's crust
and atmosphere is an important climate regulator because
carbon dioxide and other gases, such as methane, nitrous
oxide, chlorofl uorocarbons, and water vapor, allow sunlight
to pass through them, but trap the heat refl ected back from
Earth's surface. This retention of heat is called the greenhouse
effect. It results in an increase in the temperature of Earth's
surface and, more importantly, its atmosphere, thus produc-
ing global warming (
Figure 1.4).
Figure 1.4 The Greenhouse Effect and Global Warming
Short-wavelength radiation
from the Sun that is not
reflected back into space
penetrates the atmosphere
and warms Earth's surface.
Earth's surface radiates heat in the form
of long-wavelength radiation back into
the atmosphere, where some of it escapes
into space. The rest is absorbed by
greenhouse gases and water vapor
and reradiated back toward Earth.
Increased concentrations of greenhouse gases
trap more heat near Earth's surface, causing a
general increase in surface and atmospheric
temperatures, which leads to global warming.
a
c
b
 
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