Photo Courtesy of Ralph Eliason

Related Links

http://geopubs.wr.usgs.gov

http://pubs.usgs.gov/gip/volc/geysers.html

Courtesy of Ralph's Geyser's Yellowstone National Park

Literature Cited

Holden, Constance ed. 1997. Secrets of old
faithful. Science. 393

Jones, B., Robin W. Renaut and Michael R. Rosen.
2000. Microbial construction of silicieous stalactites
at geysers and hot springs: examples from the
whakarewarewa geothermal area north island, new
zealand. Palious Vol.16:73-94. File name?. Item #.
Fulltext. (Accessed 2002 March 8).

Nemiroff, R. and Jerry Bonnell. 1995. Astronomy
picture of the day. http://antwrp.gsfc.nasa.gov/apod/ap950805.html. Accessed 2002 March 10.

Tarbuck, E.J. and Frederick K. Lutgens. 2002.
Earth: an introduction to physical geology.
Upper Saddle River, NJ. Prentice Hall Inc.

The Learning Network. 2000-2002. Geysers in
the United States. http://www.infoplease.com/ipa/A0001803.html. Accessed 2002 March 11.

United States Geological Service. 2000 February
11. Abrupt physical and chemical changes during
1992-1999, anderson springs, se geysers geothermal field,
ca. http://geopubs.wr.usgs.gov/open-file/of00-037.
Accessed 2002 March 10.

United States Geological Service. 1997 January 31.
Geysers, fumaroles and hot springs. http://pubs.usgs.gov/gip/volc/geysers.html. Accessed 2002 March 8.

U.S.-Parks.com Inc. 2000-2002. Geysers and how they
work. http://www.us./parks.com/US_National_Parks/ yellowstone/yellowstone_geysers.shtml. Accessed
2002 March 8.

Wyojones' Geyser Page. 2002. Geysers/hot springs
damaged or destroyed by man. http://geology.about.com /gi/dynamic/offsite.htm?once=true&site=http://www.web-net.com/jonesy/nevadalinks.htm. Accessed 2002 March 11.

Wright, Michael. 1997. The geysers field. Geotimes. V.2: 26.

Photo Courtesy Yellowstone Park.Com

Author: Katie Baum

Creation/revision date: March 8, 2002

Geysers

Introduction

Geysers are hot springs or fountains which, occur when columns of water are forcefully ejected into the air at odd intervals. Geysers rise between 30-60 meters in the air. When the water has been ejected, it is followed by a column of steam and a loud "thunderous roar". This geological phenomenon usually occurs where underground chambers are found within igneous rock (Tarbuck and Lutgens, 2002). Geysers are found in volcanic regions throughout the world. Most notable, however, are the developments in Iceland, New Zealand, and Yellowstone National Park (The Learning Network, 2000-2).

Geologic Processes

As I mentioned in the introduction, geysers occur where underground chambers are found within igneous rock or magma reservoirs. These reservoirs remain hot and are either active or solidified (USGS, 2000). Cool groundwater enters the chambers and is heated by the surrounding rock. The water at the bottom of the chamber is under great pressure due to the overlying water's weight. Because of this pressure, water does not boil at the normal surface temperature, 100 degrees Celsius. While heat causes the water to expand, it is unable to boil which causes an eruption in which some water is forced to the surface; this reduces the pressure on the water, which remains. At this point, the cycle begins again: cool groundwater seeps into these great underground chambers (U.S.-Parks, 2000-2; Tarbuck and Lutgens, 2002). The USGS describes this same phenomenon differently explaining that "water is heated, becomes less dense and rises back to the surface along fissures and cracks"(USGS,2000). The USGS also tells us, as we see in the varying explanation of this geothermal activity, that "…their mechanisms are not completely understood"(USGS, 2000).

Photo Courtesy of Meg Streepey, University of Michigan

Products of the Geologic Process

In the 1997 October issue of Geology, geologists James Westphal and Susan Kieffer describe their findings after lowering a video camera seven meters below the surface of old Faithful. Old Faithful's shaft constricts from 20 centimeters to eleven. At a greater depth, the shaft opens into a larger chamber with a boiling mixture of steam, water and what appeared to be Carbon Dioxide bubbles. At a depth of 10.5 meters, jets of boiling water rise "nearly horizontally" from the chamber wall"(USGS, 1997). According to Westphal, this physical structure fits the standard hypothesis that "the jets fill the caverns from below, and water is forced slowly through constriction. Pressure in the lower rises and the overlying water makes its way out of the shaft (USGS, 1997).

When groundwater erupts to the surface, material in a solution is precipitated and deposited. This deposit reflects the chemical makeup of the rock, which surrounded the groundwater, during its circulation (Tarbuck and Lutgens, 2002). The earth surfaces found below the dripping water from the "overhanging edges of gesyerite rims" are sites, in which, siliceous stalactites form. The growth of these stalactites is dependent on a variety of factors: volume, temperature and silica concentration of the water at each particular site. The water that forms stalactites originates from the discharge of geysers. Microbial evidence suggests that "silica precipitation took place after these waters had cooled"(Jones, Renant and Rosen, 2000).

Impacts

Geysers represent a very fragile earth process that experiences rapid changes in terms of a geological time scale. There a many natural processes which result in the "death" of a geyser; for example, a change or move in the water or heat source influencing thermal activity. In other instances, a geyser will breech its' seal (blow up) or be destroyed by a land slide. Human beings, however, also influence the destruction of this fragile geothermal activity. Human activity is damaging to geyser activity in a variety of ways. Human can damage geysers from activity as small as throwing debris into the geyser's vent. And, of course, the development of hydroelectric projects such as geothermal drilling and power plant development poses a large threat to natural geothermal activity (Wyojones'Geyser Page, 2002).

In a specific example of the rapid changes which occur in geyser activity, the maximum temperature of a geyser cluster in Anderson Springs (near San Francisco, California) fell from 63 degrees Celsius in 1889 to 48 degrees Celsius in 1992. In 1995, however, the temperature rose again to 77 degrees Celsius and a new cluster of "boiling vents and small fumaroles formed just north of the old cluster. Along with changes in the maximum temperature, changes in the cluster pressure and gas composition changed. The causes for these changes are still undetermined (possible because the geothermal activity of geysers is not entirely understood). It is possible, however, that the withdrawal of steam by several electric power plants over the past 20 years has taken its toll. It is clear that geysers are a fragile earth process, which are quickly (on a geological time scale) effected by human behavior and use (Wright, 1997).

A Fascinating Tidbit

In August 1989, the Voyager 2 spacecraft passed by Neptune's largest moon Triton. This moon was surveyed by a robot space probe at a distance of 24,000 miles. The temperature was found to be 400 degrees Fahrenheit. A complex system of "geyser like eruptions" from small volcanoes was observed as well (Nemiroff and Bonnell, 1995).

Photo Courtesy of Embassy of Iceland website

[Links to all class members sites will be inserted here.]

Copyright ©-2001 Earlham College. Revised 25 February 2002. Send corrections or comments to baumka@earlham.edu