Bruce Lindsey, age 13, of Santa Cruz, Calif., for his question:
CAN YOU EXPLAIN GEOTHERMICS?
Geothermics is the science pertaining to the earth's inner heat. Its main practical application is in finding sources of energy and harnessing them for electrical power generation, heating, agriculture and industrial processing.
Heat deep within the crust and upper mantle of the earth is produced by decay of radioactive minerals, interactions of converging tectonic plates and upwelling of magma, the deep lying molten rock that is located in regions of crustal weakness, such as long mid ocean ridges.
Surface manifestations include volcanoes, geysers and fumaroles, hot springs, warm ground and mud pots.
The first hand drilled wells for tapping geothermal energy produced hot fluids for year round greenhouse agriculture, more than a century ago, in Hungary. Modern drilling reaches fluids and steam in natural reservoirs, heated by magma, that are 10,000 feet deep or more.
Today geothermal fluids heat districts of Budapest, a Paris suburb, all of Reykjavik and other Icelandic cities, many communities in the U.S.S.R., most of Klamath Falls, Ore., and part of Boise, Ids.
The world's largest geothermal power complex is operated today by Pacific Gas and Electric Co. at the Geysers in Sonoma County, 105 miles north of San Francisco. Sixteen units currently are in operation, with a combined generating capacity of 1,018 megawatts. Other plants are scheduled elsewhere in the western continental United States.
Smaller plants are now under study or construction in Hawaii, Utah and in California's Imperial Valley. The U.S. has a conservatively estimated capacity of 450,000 megawatts if sources of 300 degrees Fahrenheit or hotter are developed.
Geothermal power plants do not burn anything, and so no smoke pollutes the air.
Geothermal power is generated wherever water comes into contact with heated underground rocks and turns into steam. Power companies drill into areas where underground steam is trapped and direct it into the blades of steam turbines.
In areas where underground steam does not exist naturally, man can create it by injecting water into hot rocks.
Some of the world's geothermal plants produce electricity more cheaply than do ordinary power plants.
Los Alamos Scientific Laboratory in New Mexico has drilled into the hot, dry rock beneath Valles Caidera and injected surface water that returns as superheated steam, which could be used to generate electricity.
New Zealand, Mexico, El Salvador, Japan, Iceland, Italy, the Philippines, Indonesia, China, the Azores, Kenya and the Soviet Union all have geothermal power plants today and another 50 nations are in the exploratory and planning stages for similar geothermal developments.