Earlham College - Geology 211 - Geysers

Geysers are essentially hot springs that become thermodynamically and/or hydrodynamically unstable. They are made when rain water soaks into the ground and percolates into deep cracks in the earth. There, the water may encounter hot rocks that warm the water well over the boiling point. The hot water pushes through the cracks and emerges as either steam or water. Geysers erupt randomly or regularly, depending on the conditions of the underground passageways. The intervals between eruptions range from minutes to years, and an eruption may last anywhere from a few minutes to few hours. The height of a geyser may vary from 3 feet to 328 feet. (Leathers/Geysers) They are extremely rare on the surface of the earth, indicating that a complex set of conditions must be exactly right for geysers to occur.

These three critical components are:

1 An abundant supply of water
2 An intense source of heat
3 Special plumbing systems

The first two critera are naturally very abundant. The third, the correct geology to support geyser plumbing, is very rare. Geyser plumbing must be water and pressure tight. Scientists believe the answer to this difficult problem lies with a volcanic rock called rhyolite. High in silica, rhyolite composes most of the geyser fields in the world. The only problem is that rhyolite fields are scarce.

Geologic Processes

The dominant geologic process that is resposible for the majority of all geysers is volcanism. Geysers are essentially linked to volcanoes because they require intense geothermal heat close to the surface. Water flows through the fractured rocks and into the chambers. This filling and flashing of the water against the hot rocks then causes a sudden discharge of gas, steam, and water from the chamber. This makes geysers the only natural two-phase discharge feature of all hydrothermal systems.(Sigurdsson/p.851)

There are less than 7000 geysers in the world, and places where many geysers can be found in one area include Iceland, New Zealand, and the U.S. One of the most famous geyser sites is Yellowstone National Park. There are more than 3000 geysers and hot springs in the park, including the most famous geyser Old Faithful.(Leather/Geysers)

Products of the Geologic Process

Geysers, like all other geological processes, are dynamic. Newly formed geysers are discovered constantly, just as others become inactive. This, of course, is due to the fact that the earth's tectonic plates are unstable and constantly changing, and the chambers that make geysers possible are subject to alterations from earthquakes and volcano eruptions. There is still much to be learned about geysers, and this field of study could quite possibly open up new areas of research to be used to society's advantage.

Impacts

Geysers have impacted the earth and it's inhabitants for countless years, if only by their majestic and mysterious behavior. Now, we are realizing how much more geysers can do for us. 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. Could geysers save the lives of people by predicting earthquakes?(Geysers/msu)

Another way geysers may affect us is in the use of power. Steam from the geyser is purified, transported in insulated pipes, pressurized, and made into electrical power. These geothermal power plants can be found in northern California, Nevada, Utah, and Hawaii.

"Given the magnitude of the resource and it's ability to provide energy with an environmental impact significantly less than that of energy produced by combustion of fuels, geothermal energy must become a major potential source of energy for the future."(Geoscience Canada/40)