Generally found in areas of young volcanic activity, geysers are hot springs that erupt in a column of steam or hot water. They are created by surface water that percolates down through the earth's surface into high-temperature regions surrounding a reservoir of magma which heats the rock. When the water makes contact with these rocks, it warms the water until it is well over its boiling point. The water becomes less dense and rises back to the surface along fissures and cracks in the earth's crust, always in geothermal areas.
Geysers erupt with varying regularity depending on the condition of their underground passageways.
It is thought by many scientists that geysers are predictors of earthquakes. Only sixty hours before the October 1989, 7.1 - magnitutude quake in the San Francisco Bay Area, Old Faithful's usually dependable period suddenly lengthened too more that 100 minutes. Scientists believe that small earth movements preceding the quake could have altered the size of the resevoir beneath the geyser, effecting its pressure and water flow rate. Geysers also affect us in our use of power. Steam from geysers is purified, transported in pipes, pressurized, and turned into electrical power.