Terrance Long, age 12, of Tulsa, Oklahoma, for his question:
What exactly are geysers?
People travel miles to watch the geysers spout up their steamy foun¬tains from the ground. But these show offs are much more than just tourist attractions. One possibility to ease the present energy crisis is geothermal energy, which is the underground heat that boils the geysers.
Geysers are related to hot springs and funaroles. All of them are powered by vast reservoirs of heat, trapped deep down in the earth's crust. These mysterious regions occur in warm and cold climates like Alaska and Africa, Iceland and Aew Zealand, the Andes and Yellowstone National Park.
Everywhere there is heat down underground. On the average, for every 60 feet we descend, the temperature rises about one degree Fahrenheit. However, in geyser territory, the temperature may be 400 degrees at 500 feet below the surface. These zones of geothermal energy seem to be left from fairly recent volcanic upheavals.
Possible pockets of molten ma ma are trapped miles below the surface, or maybe old lava flows intruded between deep layers of the crust and failed to cool. In any case, the buried heat tries to escape through cracks and crevices to the surface. When ground water percolates through the buried hot rocks, it ushes up to the surface in bubbling hot springs.
A geyser is actually a hot spring that spurts. Its behavior is very complicated and scientists are not exactly certain about how it works. But since no two geysers are alike, they agree that the particular underground rock formation has a lot to do with it.
The typical roots of a geyser may include a series of connected cracks and cavities reaching down perhaps 1,000 feet. A crooked vent leads to the surface. Groundwater from rainfall percolates into the cavities and is heated by the rocks. Deep underground, the water is under pressure, and extra pressure raises the boiling point of water.
Down at 500 feet, the water would not boil until it reached 395 decrees Fahrenehit. At 300 feet it would boil at 356 degrees and near the surface at the normal 212 degrees. This would fill the underground kettle with levels of superheated water. Eventually the surface level would boil and slop over. This would release pressure down through the plumbing. Suddenly all the superheated water flashes into steam and erupts high above the surface in a foamy fountain.
This theory most likely explains what happens. In any case, where there is one geyser there are bound to be others, large and small. All of them occur in regions of geothermal energy where rocks are permeated by groundwater.