Geothermal Energy


Matt Arnold
9/17/96
Physics 009
Professor Arns

The human population is currently using up its fossil fuel supplies at
staggering rates. Before long we will be forced to turn somewhere else for
energy. There are many possibilities such as hydroelectric energy, nuclear
energy, wind energy, solar energy and geothermal energy to name a few. Each one
of these choices has its pros and cons. Hydroelectric power tends to upset the
ecosystems in rivers and lakes. It affects the fish and wild life population.
Nuclear energy is a very controversial subject. Although it produces high
quantities of power with relative efficiency, it is very hard to dispose of the
waste. While wind and solar power have no waste products, they require enormous
amounts of land to produce any large amounts of energy. I believe that
geothermal energy may be an alternative source of energy in the future. There
are many things that we must take into consideration before geothermal energy
can be a possibility for a human resource. I will be discussing some of these
issues, questions, and problems.
In the beginning when the solar system was young, the earth was still
forming, things were very different. A great mass of elements swirled around a
dense core in the middle. As time went on the accumulation elements with
similar physical properties into hot bodies caused a slow formation of a
crystalline barrier around the denser core. Hot bodies consisting of iron were
attracted to the core with greater force because they were more dense. These
hot bodies sunk into and became part of the constantly growing core. Less dense
elements were pushed towards the surface and began to form the crust. The early
crust or crystalline barrier consisted of ultra basic, basic, calc-alkaline, and
granite. The early crust was very thin because the core was extremely hot. It
is estimated that the mantel e 200 to 300 degrees Celsius warmer than it is
today. As the core cooled through volcanism the crust became thicker and cooler.
The earth is made up of four basic layers, the inner solid core, the outer
liquid core, the mantel and the lithosphere and crust. The density of the
layers gets greater the closer to the center of the earth that one gets. The
inner core is approximately 16% of the planet\'s volume. It is made up of iron
and nickel compounds. Nobody knows for sure but the outer core is thought to
consist of sulfur, iron, phosphorus, carbon and nitrogen, and silicon. The
mantel is said to be made of metasilicate and perovskite. The continental crust
consists of igneous and sedimentary rocks. The oceanic crust consists of the
same with a substantial layer of sediments above the rock.
The crust covers the outer ridged layer of the earth called the
lithosphere. The lithosphere is divided into seven main continental plates.
These continental plates are constantly moving on a viscous base. The viscosity
of this base is a function of the temperature. The study of shifting
continental plates is called Plate Tectonics. Plate Tectonics allows scientists
to locate regions of geothermal heat emission. Shifting continental plates
cause weak spots or gaps between plates where geothermal heat is more likely to
seep through the crust. These gaps are called Subduction Zones. Heat emission
from subduction zones can take many forms, such as volcanoes, geysers and hot
springs. When lateral plate movement induced gaps occur between plates,
collisions occur between other plates. This results in partial plate
destruction. This causes mass amounts of heat to be produced due to frictional
forces and the rise of magma from the mantle through propagating lithosphere
fractures and thermal plumes sometimes resulting in volcanism. During plate
movement, continental plates are constantly being consumed and produced changing
plate boundaries. When collisions between plates occur, the crust is pushed up
sometimes forming ranges of mountains. This is the way that most Midoceanic
ranges were formed. Continental plates sometimes move at rates of several
centimeters per year. Currently the Atlantic ocean is growing and the Pacific
ocean is shrinking due to continental plate movement.
In Rome people first used geothermal resources to heat public bath
houses that were used for bathing or balneology. The mineral water was thought
to be therapeutic. The minerals in the water have been used since the beginning
of time. Through out the years geothermal heated water or steam has been used
in many different systems from heating houses and baths to being a source of
boric acids and salts. Today geothermal fluids provide energy for electricity
production and mechanical work. Boric acid is still extracted and sold. Other
byproducts of geothermal heated liquid are carbon dioxide, potassium