Page 493 - 9780077418427.pdf

/Users/user-f465/Desktop
tiL12214_ch18_455-476.indd Page 470 9/3/10 6:21 PM user-f465
tiL12214_ch18_455-476.indd Page 470 9/3/10 6:21 PM user-f465 /Users/user-f465/Desktop

Science and Society

Geothermal Energy
eothermal energy means earth (geo) In addition to producing electricity, Geothermal energy is considered to
Gheat (thermal) energy, or energy in the geothermal hot water is used directly for be one of the renewable energy resources
form of heat from Earth. Beneath the sur- space heating. Space heating in individual since the energy supply is maintained
face of Earth is a very large energy resource houses is accomplished by piping hot water by plate tectonics. Currently, geother-
in the form of hot water and steam that can from one geothermal well. District systems, mal energy production is ranked third
be used directly for heat or converted to on the other hand, pipe hot water from one behind hydroelectricity and biomass but
electricity. or more geothermal wells to several build- ahead of solar and wind. It has been esti-
Most of the U.S. geothermal resources ings, houses, or blocks of houses. Currently, mated that known geothermal resources
are located in the western part of the geothermal hot water is used in individual could supply thousands of megawatts more
nation where the Juan de Fuca Plate is sub- and district space-heating systems at more power beyond current production, and
ducted beneath the continental lithosphere. than 120 locations. There are more than development of the potential direct-use
The Juan de Fuca partially melts, form- 1,200 potential geothermal sites that could applications could displace the use—and
ing magma that is buoyed toward Earth’s be developed to provide hot water to more greenhouse gas emissions—of 18 million
surface, erupting as volcanoes (see Fig- than 370 cities in eight states. The creation barrels of oil per year.
ure 19.25). This subduction is the source of such geothermal districts could result in
of heating for the hot water and steam a savings of up to 50 percent over the cost of
QUESTIONS TO DISCUSS
resources in 10 western states. There are natural gas heating.
also geothermal resources in Hawaii from a Geothermal hot water is also used Discuss with your group the following
different geothermal source. directly in greenhouses and aquaculture questions concerning the use of geothermal
One use of geothermal energy is to facilities. There are more than 35 large energy:
generate electricity. Geothermal power geothermal-energized greenhouses rais-
1. Why is the development of geothermal
plants are located in California (10 sites), ing vegetables and flowers and more than
energy not proceeding more rapidly?
Hawaii, Nevada (10 sites), Oregon, and 25 geothermal- energized aquaculture facili-
2. Should the government provide
Utah (2 sites). These sites have a total gen- ties raising fish in Arizona, California, Colo-
incentives for developing geothermal
erating capacity of 2,700 megawatts (MW), rado, Idaho, Montana, Nevada, New York,
resources? Give reasons for your
which is enough electricity to supply the Oregon, South Dakota, Utah, and Wyoming
answer.
needs of 3.5 million people. The world’s (see http://geoheat.oit.edu/dusys.htm). A
largest geo thermal power plant is located food dehydration facility in Nevada, for 3. What are the advantages and dis -
at the Geysers Power Plant in northern example, uses geothermal energy to pro- advantages of a government-controlled
California. Dry steam provides the energy cess more than 15 million pounds of dried geothermal energy industry?
for 23 units at this site, which generate more onions and garlic per year. Other uses 4. As other energy supplies become
than 1,700 MW of electrical power. All of of geothermal energy include laundries, depleted, who should be responsible
the other sites use hot water rather than swimming pools, spas, and resorts. Over for developing new energy supplies,

steam to generate electricity, with a total 200 resorts are using geothermal hot water investor-owned industry or government
generating capacity of 1,000 MW. in the United States. agencies?

are engaged in a continual cycle of change. Oceanic crust
is subducted, melted, then partly returned to the crust as
volcanic igneous rocks in island arcs and along continental CONCEPTS Applied
plate boundaries. Other parts of the subducted crust become
mixed with the upper mantle, returning as new crust at
diverging boundaries. The materials of the crust and the man- New Earthquakes and Volcanoes
tle are thus cycled back and forth in a mixing that may include Locate and label the major plates of the lithosphere on
the deep mantle and the core as well. There is more to this an outline map of the world according to the most recent
story of a dynamic Earth that undergoes a constant change. findings in plate tectonics. Show all types of boundaries
The story continues in the next chapters with different cycles and associated areas of volcanoes and earthquakes.
to consider.

470 CHAPTER 18 Plate Tectonics 18-16