DESCRIPTION:
Geothermal Energy and Hydrothermal Activity
Fumaroles, Hot Springs, Geysers

Hydrothermal - pertains to hot water or the action of heated water, often considered heated by magma or in association with magma.

Hydrothermal alteration - alteration of rocks or minerals by the reaction of hot water (and other fluids) with pre-existing rocks. The hot water is generally heated groundwater and dissolved minerals.

[Image,37K,JPG]
Hot Spring, Yellowstone National Park
-- USGS Photo by David E. Wieprecht

Geysers, fumaroles (also called solfataras), and hot springs are generally found in regions of young volcanic activity. Surface water percolates downward through the rocks below the Earth's surface to high-temperature regions surrounding a magma reservoir, either active or recently solidified but still hot. There the water is heated, becomes less dense, and rises back to the surface along fissures and cracks. Sometimes these features are called "dying volcanoes" because they seem to represent the last stage of volcanic activity as the magma, in depth, cools and hardens.

Erupting geysers provide spectacular displays of underground energy suddenly unleashed, but their mechanisms are not completely understood. Large amounts of hot water are presumed to fill underground cavities. The water, upon further heating, is violently ejected when a portion of its suddenly flashes into steam. This cycle can be repeated with remarkable regularity, as for example, Old Faithful Geyser in Yellowstone National Park, which has erupted on an average of about once every 65 minutes.

Fumaroles, which emit mixtures of steam and other gases, are fed by conduits that pass through the water table before reaching the surface of the ground. Hydrogen sulfide (H2S), one of the typical gases issuing from fumaroles, readily oxidizes to sulphuric acid and native sulfur. This accounts for the intense chemical activity and brightly colored rocks in many thermal areas.

Hot springs occur in many thermal areas where the surface of the Earth intersects the water table. The temperature and rate of discharge of hot springs depend on factors such as the rate at which water circulates through the system of underground channelways, the amount of heat supplied at depth, and the extent of dilution of the heated water by cool ground water near the surface.

Geothermal energy. can be harnessed from the Earth's natural heat associated with active volcanoes or geologically young inactive volcanoes still giving off heat at depth. Steam from high-temperature geothermal fluids can be used to drive turbines and generate electrical power, while lower temperature fluids provide hot water for space-heating purposes, heat for greenhouses and industrial uses, and hot or warm springs at resort spas. For example, geothermal heat warms more than 70 percent of the homes in Iceland, and The Geysers geothermal field near Santa Rosa, in Northern California produces enough electricity to meet the power demands of San Francisco. The Geysers area is the largest geothermal development in the world. In addition to being an energy resource, some geothermal waters also contain sulfur, gold, silver, and mercury that can be recovered as a byproduct of energy production.

MORE Geothermal Energy Information

The Casa Diablo Hot Springs site is located on the southwestern edge of the resurgent dome along a major fault system. The fault forms the east side of the down-dropped block that transects the resurgent dome. This down-dropped block is called the medial graben. Three binary-cycle generators built here in 1985 and 1990 produce about 45 megawatts of electricity. Wells, each about 200 meters deep, supply the powerplants with 170 degree water. Heat exchangers transfer the thermal energy from the water to isobutane, which vaporizes and drives turbine generators.

The Coso volcanic field is also well known as a geothermal area. Fumaroles are present along faults bounding the rhyolite-capped horst and locally within the rhyolite field. A multi-disciplinary program of geothermal assessment carried out in the 1970s defined a potential resource of 650 megawatts electric with a nominal life span of 30 years. Judged by the youthfulness of the rhyolite lavas and by a zone of low seismic velocity crust roughly beneath the rhyolite, a magma body may be the source of thermal energy for the geothermal system. Commercial development beginning in the 1980's resulted in the startup of a geothermal steam-driven 3-MW electric power plant in 1987.

Coso Volcanic Field Menu

Present thermal activity at Mount Hood is in fumarole fields near Crater Rock, at the apex of a semi-circular zone of fumaroles and hydrothermally-altered, heated ground. In summer 1987, maximum ground temperatures were near 85 degrees C and maximum fumarole temperatures were about 92 degrees C, slightly above the boiling point of water at 3,100 meters. Many of the fumaroles are actively precipitating crystalline sulfur. Comparison of modern and historical photographs shows that the amount of perpetually snow-free ground surrounding the fumarole fields has been increasing since last century. Until the 1980 eruption of Mount St. Helens, the only volcanically related human fatality in the Cascades occurred in the thermal area at Mount Hood in 1934, when a climber exploring ice caves in Coalman Glacier melted by fumaroles suffocated in the oxygen-poor gas.

Mount Hood Volcano Menu

Baker81_gas_sampling_fumarole_mount_baker_1981.jpg
Sampling gases, fumarole, on top of Mount Baker, Washington.
USGS Photograph taken in 1981 by W. Chadwick.
[medium size] ... [large size] ... [TIF Format, 24 M]

Most hydrothermal activity at Mount Baker is concentrated within Sherman Crater, although a small area of fumaroles, known as the Dorr Fumarole Field, is present on the north flank of the volcano at an altitude of 2,300 to 3,500 meters.

Mount Baker Volcano Menu

Gravity and teleseismic studies suggest that a large silicic magma chamber, approximately 14 kilometers in diameter, lies 7 kilometers and deeper beneath the (Clear Lake) volcanic field. This reservoir is thought to be the heat source for the Geysers geothermal field (on the southwest side of the volcanic field), which is the largest producing geothermal field in the world, with installed electrical generating capacity of around 2,000 megawatts in 1988, enough electricity for about two cities the size of San Francisco.

Clear Lake Volcanic Field Menu

In May 1914 Lassen Peak burst into eruption, beginning a seven-year cycle of sporadic volcanic outbursts. The climax of this episode took place in 1915, when the peak blew an enormous mushroom cloud some seven miles into the stratosphere. The reawakening of this volcano, which began as a vent on a larger extinct volcano known as Tehama, profoundly altered the surrounding landscape. The area was made a National Park in 1916 because of its significance as an active volcanic landscape. The park is a compact laboratory of volcanic phenomena and associated thermal features (except true geysers). It is part of a vast geographic unit - a great lava plateau with isolated volcanic peaks - that also encompasses Lava Beds National Monument, California, and Crater Lake National Park, Oregon.

Before the 1980 eruption of Mount Saint Helens in Washington, Lassen Peak was the most recent volcanic outburst in the contiguous 48 states. The peak is the southernmost volcano in the Cascade Range, which extends from here into Canada. The western part of the park features great lava pinnacles (huge mountains created by lava flows), jagged craters, and steaming sulphur vents. It is cut by spectacular glaciated canyons and is dotted and threaded by lakes and rushing clear streams. Snowbanks persist year-round and beautiful meadows are spread with wildflowers in spring. The eastern part of the park is a vast lava plateau more than one mile above sea level. Here are found small cinder cones (Fairfield Peak, Hat Mountain, and Crater Butte). Forested with pine and fir, this area is studded with small lakes, but it boasts few streams. Warner Valley, marking the southern edge of the Lassen Plateau, features hot spring areas (Boiling Springs Lake, Devils Kitchen, and Terminal Geyser). This forested, steep valley also has gorgeous large meadows. ...

Lassen geothermal area - Sulphur Works, Bumpass Hell (largest), Little Hot Springs Valley, Boiling Springs Lake, Devils Kitchen, and Terminal Geyser - offer bubbling mud pots, steaming fumaroles, and boiling water. Some of these thermal features are getting hotter. Scientists think that Lassen Park and Mount Shasta are the most likely candidates in the Cascades to join Mount Saint Helens as active volcanoes.

Bumpass Hell:

This is Lassen's most spectacular and diversified hydrothermal area, with hot springs, mudpots, fumaroles, and mud volcanoes.

Sulphur Works:

... hydrothermal area is the most accessible hot springs area in Lassen Volcanic National Park. It is thought to be part of the central vent system of ancient Mount Tehama ... A short paved trail leads to sputtering hot springs, steaming fumaroles and hot bubbling mudpots. ... Slippery clay and thin crusty coverings could lead to a dunking in 195 degree F (76 degrees C) water and mud. Most water in the thermal areas of the park contains sulphurous or sulphuric acid ... The odor is mainly that of hydrogen sulphide. Much of the white clay is tinted yellow, tan, or pink by minerals, chiefly iron oxides.

Lassen Peak Menu

The Deschutes National Forest is one of the few national forests with potential for geothermal energy development. Such potential offers a great economic opportunity for the area, while providing a long-term renewable energy resource.

Here in the Pacific Northwest and the Western Pacific, a series of volcanoes formed a "Ring of Fire" where underground heat has escaped. These volcanoes range from dormant ones, such as the Three Sisters in central Oregon and Mount Fujiyama in Japan, to active ones, such as Mount St. Helens in southwestern Washington and Mount Pinatubo in the Philippines. This energy can be tapped by drilling wells, usually less than 10,000 feet deep, to bring hot fluids or steam to the surface where it can be used to generate electricity. The world's largest geothermal development is located at The Geysers near San Francisco. This facility produces about twice the amount of energy as the Bonneville Dam on the Columbia River near Portland, which produces about 1,000 megawatts, enough for a city of one million people.

Geologically young volcanoes found in our area suggest that central Oregon may contain some of the best prospects for geothermal exploration in the continental United States. One study done at Newberry Volcano estimated the energy potential to be up to 13,000 megawatts. Another study by Bonneville Power Administration estimates a 16,000 megawatt potential. ...

Newberry Volcano holds the most promise for a viable geothermal development. Located southeast of Bend, Newberry Volcano covers 500 square miles. Hot springs in the caldera have water temperatures ranging from 95 to 175 degrees Fahrenheit. In 1990, the Newberry Volcano area was designated as Newberry National Volcanic Monument. This Congressional designation restricts geothermal development within the caldera, but provides for exploration outside the Monument's boundaries. Before any development occurs, considerable effort is spent on exploration. Test wells drilled to date show that they need to be over 2,000 feet deep to reach beyond the cool ground water, and possibly go 1 to 2 miles or more deep to reach high temperatures and fluids. ...

In June 1994, the Deschutes National Forest and the Prineville District Bureau of Land Management issued a joint Record of Decision to implement the Newberry Geothermal Pilot Project. The decision was based on the environmental analysis and Final Environmental Impact Statement, and included mitigation measures and an extensive monitoring program. In October 1994, the Bonneville Power Administration released their Record of Decision adopting the same alternative as Forest Service and BLM. The approved project included exploration, development, and production operations for 14 well pads, a 33-megawatt power plant, a 115-kv transmission line, and supporting facilities on the west flank of Newberry Volcano, outside of the Newberry National Volcanic Monument. Approval from all three federal agencies allowed the operator, CE Exploration Company, to begin implementation. ...

Newberry Caldera Menu

Haroharo Caldera and Okataina Volcanic Center lie in the northern half of the Taupo Volcanic Zone (TVZ), a region of intense volcanic and geothermal activity.

Rotorua Caldera formed as a result of eruption of the 200 cubic kilometer (dense-rock equivalent) Mamaku ignimbrite. Subsequent lava domes in the calder, from 1 to 10 cubic kilometers in volume, have not been dated. No eruptions (other than hydrothermal explosions) are known within the past 10,000 years, but the Rotorua-Whakarawarewa area is known for numerous hot springs, geysers, and other geothermal features that support a significant tourist industry.

New Zealand Volcanoes and Volcanics Menu

Active fumaroles were recognized at the summit of Mount Rainier at the time of the first authenticated climb to the top of the volcano in 1870, and the lavas of the summit cone have locally been hydrothermally altered to a loose, sandy, clay-bearing material. ... The evidence now available clearly indicates that all the large clayey lahars at Mount Rainier were derived from areas of hydrothermally altered rock on the volcano.

Mount Rainier Information -- includes Hydrothermal System Section

Mount Rainier Volcano Menu

The Salton Buttes lie within the Salton Sea geothermal field, where temperatures at 1.5 to 2.5 kilometers reach 360 degrees C, and sediments of the Colorado River delta are begin metamorphosed to greenschist facies.

The Salton Sea geothermal field lies in the Salton Trough, the landward extension of the Gulf of California, an area of active crustal spreading. The Salton Buttes volcanoes lie within the Salton Sea geothermal field where temperatures measured in wells drilled for geothermal brines range up to 360 degrees C at depths of 1,500 to 2,500 meters (Helgeson, 1968). The wells produce a hot brine containing up to 160,000 ppm of dissolved solids, chiefly Cl, Na, K, Ca, and Fe (White, 1968). Under the influence of this hot saline brine, the sediments of the Salton Trough are being transformed into metamorphic rocks of the greenschist facies (Muffler and White, 1969).

Salton Buttes Menu

The extensive Steamboat Springs geothermal area, containing numerous hot springs and steam vents, is located just west of U.S. 395 and south of the Mount Rose Highway. Steamboat Springs, so named for the huffing and puffing sight and sound of the escaping steam, is just south of the emigrant trail that crossed the Truckee Meadows on its way to California and by the 1850s the springs had become a favorite camping ground for westward bound travelers. By 1862 Steamboat Springs had a commercial bathhouse, cottages, and a hospital. With the development of the Comstock Mines, Steamboat became a junction point on the road between Reno and Virginia City and, later, became a station on the Virginia &Truckee Railroad. In the 1870s, Steamboat was a fashionable spa, with a fine hotel, drugstore, cottages, and medicinal baths but, by 1900, the resort had almost completely deteriorated. Drilling and geothermal exploration in the area over the past 30 or so years has caused the huffing and puffing (active geysering) to cease, but steam still vents at times. A small resort still operates on the east side of U.S. 395, and the Steamboat Post Office, established in 1880, is still operating.

The springs at Steamboat are near boiling, and exploration and production steam wells at the three geothermal generating plants have encountered temperatures as high as 190 degrees C. The thermal waters contain trace amounts of metals, including mercury, antimony, arsenic, silver, and gold. Small amounts of stibnite, gold, silver, and cinnabar have been deposited in both hot-spring sinter and in the altered wall rock adjacent to the hot-spring vents.

At the present time, there are three geothermal power-generating plants in operation in the Steamboat area. One plant, consisting of two 12-MW, air-cooled, binary units, is located on the low terrace near the intersection of U.S. 395 and State Route 431. The plant was brought on line in December 1992. An older 7-MW plant is located about 1/3 mile to the west, slightly higher on the terrace. These plants are operated by S.B. Geo, Inc. The geothermal fluid cycle at these plants is completely contained and the fluids are injected back into the ground (closed binary-cycle system). The existing resource is expected to last 30 years or more and can support an additional 36 MW of production capacity. Higher on the side of the Steamboat Hills (near the steam plume) Yankee Caithness operates a 14.4-MW flash turbine system. The Yankee Caithness Steamboat plant came on line in 1988, and the produced power is purchased by Sierra Pacific Power Co. on a 30-year contract.

Nevada is second only to California in installed geothermal capacity. In 1999, Nevada produced approximately 1.6 million MWh of geothermal power, with a sales value of about $90 million. The lower generating complex a Steamboat Springs is the second largest in Nevada. In 1999, the Steamboat geothermal plants generated about 475,000 MWhr, or about 30 percent of the total Nevada geothermal power output.

Nevada Volcanoes and Volcanics Menu

[Image,37K,JPG]
Hot Spring, Yellowstone National Park
-- USGS Photo by David E. Wieprecht

Geysers, fumaroles (also called solfataras), and hot springs are generally found in regions of young volcanic activity. Surface water percolates downward through the rocks below the Earth's surface to high-temperature regions surrounding a magma reservoir, either active or recently solidified but still hot. There the water is heated, becomes less dense, and rises back to the surface along fissures and cracks. Sometimes these features are called "dying volcanoes" because they seem to represent the last stage of volcanic activity as the magma, in depth, cools and hardens.

Erupting geysers provide spectacular displays of underground energy suddenly unleashed, but their mechanisms are not completely understood. Large amounts of hot water are presumed to fill underground cavities. The water, upon further heating, is violently ejected when a portion of its suddenly flashes into steam. This cycle can be repeated with remarkable regularity, as for example, Old Faithful Geyser in Yellowstone National Park, which has erupted on an average of about once every 65 minutes.

Fumaroles, which emit mixtures of steam and other gases, are fed by conduits that pass through the water table before reaching the surface of the ground. Hydrogen sulfide (H2S), one of the typical gases issuing from fumaroles, readily oxidizes to sulphuric acid and native sulfur. This accounts for the intense chemical activity and brightly colored rocks in many thermal areas.

Hot springs occur in many thermal areas where the surface of the Earth intersects the water table. The temperature and rate of discharge of hot springs depend on factors such as the rate at which water circulates through the system of underground channelways, the amount of heat supplied at depth, and the extent of dilution of the heated water by cool ground water near the surface.

The Yellowstone caldera region hosts the world's largest know hydrothermal system, highlighted by numerous geysers. This hydrothermal system accounts for an average heat flow from the caldera area 40 times greater than the global average. Although the latest eruptions were approximately 70,000 years ago, the immense hydrothermal system and a variety of geophysical characteristics indicate that magma still underlies the Yellowstone caldera at a shallow depth. A large negative gravity anomaly, low magnetic intensity, high electrical conductivity, shallow swarm seismicity, and large delays and high attenuation of seismic waves are all consistent with this inference.

Yellowstone Caldera Menu

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