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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 649 records · Page 36Linked to original sources
USGS1985

SEISMIC STUDY OF THE AGUA DE PAU GEOTHERMAL PROSPECT, SAO MIGUEL, AZORES.

A 16 station array was operated over the 200 km**2 central portion of Sao Miguel utilizing 8 permanent Instituto Nacional de Meterologia e Geofisica stations and 8 USGS portable stations. Forty four local events with well constrained solutions and 15 regional events were located. In addition, hundreds of unlocatable seismic events were recorded. The most interesting seismic activity occurred in a swarm on September 6 and 7, 1983 when over 200 events were recorded in a 16 hour period. The seismic activity around Agua de Pau was centered on the east and northeast slopes of the volcano. The data suggest a boiling hydrothermal system beneath the Agua de Pau volcano, consistent with a variety of other data.

Conference Paper↗
USGS1985

CHEMISTRY OF LOW-TEMPERATURE GEOTHERMAL WATERS AT KLAMATH FALLS, OREGON.

Chemical and isotopic analyses of well discharges indicate that in the aquifer mixing occurs between shallow cold groundwater containing 2. 0 TU tritium and a deeper tritium-free thermal groundwaer at 100 to 120 degree C. This deeper water apparently results from the mixing of old, tritium-free cold groundwater and deep thermal groundwater at about 190 degree C and 120 mg/kg Cl. The temperature and chlorinity of the deep thermal water are based on SO//4-isotope and silica geothermometers and chloride and silica mixing models.

Conference Paper↗
USGS1989

Assessment of geothermal resources at Newcastle, Utah

Integrated geology, geophysics, and geochemistry studies in the Newcastle area of southwest Utah are used to develop a conceptual geologic model of a blind, moderate-temperature hydrothermal system. Studies using 12 existing and 12 new, thermal gradient test holes, in addition to geologic mapping, gravity surveys, and other investigations have helped define the thermal regime. Preliminary results indicate that the up-flow region is located near the west-facing escarpment of an adjacent mountain range, probably related to the bounding range-front fault. Chemical geothermometers suggest equilibration temperatures ranging from 140??C to 170??C. The highest temperature recorded in the system is 130??C from an exploration well drilled by the Unocal Corporation.

Conference Paper↗
USGS1990

Geologic map and geothermal assessment of the Mount Adams volcanic field, Cascade Range of southern Washington

More than 60 Quaternary vents make up the basalt-to-rhyodacite Mount Adams volcanic field and have erupted scoriae and lavas with a total volume of >370 km3. The Mount Adams andesite-dacite stratocone itself is a compound edifice that includes the high cone above 2300 m (20-10 ka), remnants of at least two earlier andesite-dacite cones as old as 0.5 Ma, and 7 Holocene flank vents. Four other Holocene vents and tens of vents contemporaneous with Mount Adams are peripheral to the stratocone. All of these vents, including Mount Adams, lie within a N-S eruptive zone 55 km long and 5 km wide. The age of all known Mount Adams silicic products (>100 ka) and the heterogeneous mafic compositions of the summit cone and Holocene lavas make it unlikely that the stratocone is underlain by an upper-crustal reservoir. Rather, the stratocone at the focus is built up of fractionated hybrid magmas that rise from MASH zones (melting-assimilation-storage-homogenization). The pyroclastic core of breccia and scoria at Mount Adams has undergone acid-sulfate leaching and deposition of alunite, kaolinite, silica, gypsum, sulfur, and Fe-oxides and has been a constant source of avalanches and debris flows. Most heat supplied from depth to the fumarolically altered core is dispersed by the high precipitation rate and high permeability of the rubbly lava flows so that a hydrothermal convection pattern is not maintained. Summit-restricted fumaroles are weak and diffuse.

Conference Paper↗
USGS1993

Dynamic behavior of Kilauea Volcano and its relation to hydrothermal systems and geothermal energy

Exploitation of hydrothermal systems on active basaltic volcanoes poses some unique questions about the role of volcanism and hydrothermal system evolution. Volcanic activity creates and maintains hydrothermal systems while earthquakes create permeable fractures that, at least temporarily, enhance circulation. Magma and water, possibly hydrothermal water, can interact violently to produce explosive eruptions. Finally, we speculate on whether volcanic behavior can be affected by high rates of heat extraction.

Conference Paper↗
USGS1993

Non-shear focal mechanisms of earthquakes at The Geysers, California and Hengill, Iceland, geothermal areas

Several thousand earthquakes were recorded in each area. We report an initial investigation of the focal mechanisms based on P-wave polarities. Distortion by complicated three-dimensional crustal structure was minimized using tomographically derived three-dimensional crustal models. Events with explosive and implosive source mechanisms, suggesting cavity opening and collapse, have been tentatively identified at The Geysers. The new data show that some of these events do not fit the model of tensile cracking accompanied by isotropic pore pressure decreases that was suggested in earlier studies, but that they may instead involve combination of explosive and shear processes. However, the confirmation of earthquakes dominated by explosive components supports the model that the event are caused by crack opening induced by thermal contraction of the heat source.

Conference Paper↗
USGS1993

Heat-flow studies in the northwest geysers geothermal field, California

Temperature and thermal conductivity data were acquired from 3 idle production wells in the Northwest Geysers. Heat-flow profiles derived from data recorded in the caprock which overlies the steam reservoir reveal a decrease of heat flow with depth in 2 of the 3 wells. These observations contradict the generally accepted theory that conductive heat flow is constant with depth within The Geysers caprock. There are several possible explanations for this, but the available data suggest that these profiles reflect a local recession or cooling of the reservoir top within the past 5000 to 10000 years.

Conference Paper↗
USGS1993

Taming a wild geothermal research well in yellowstone national park

In November 1992 the valve at the top of a U.S. Geological Survey drill hole in Yellowstone National Park parted from the casting as a result of corrosion. This allowed uncontrolled venting of boiling water and steam from the well at an estimated liquid flow rate of about 25-50 gallons per minute. A flow diverter assembly was designed, fabricated and installed on the well within 16 days, which allowed drill rods to be safely stripped into the well through on annular Blow-Out Preventer. Once this was accomplished it was a relatively routine matter to set a packer in the casting and cement the well shut permanently. The drill hole was brought under control and cemented shut within 18 days of the wellhead failure at a total cost of $47,066, which was about $5,000 less than anticipated.

Conference Paper↗
USGS1976

Geology and geophysics of the southern Raft River Valley geothermal area, Idaho, USA

The Raft River valley, near the boundary of the Snake River plain with the Basin and Range province, is a north-trending late Cenozoic downwarp bounded by faults on the west, south, and east. Pleistocene alluvium and Miocene-Pliocene tuffaceous sediments, conglomerate, and felsic volcanic rocks aggregate 2 km in thickness. Large gravity, magnetic, and total field resistivity highs probably indicate a buried igneous mass that is too old to serve as a heat source. Differing seismic velocities relate to known or inferred structures and to a suspected shallow zone of warm water. Resistivity anomalies reflect differences of both composition and degree of alteration of Cenozoic rocks. Resistivity soundings show a 2 to 5 ohm·m unit with a thickness of 1 km beneath a large part of the valley, and the unit may indicate partly hot water and partly clayey sediments. Observed self-potential anomalies are believed to indicate zones where warm water rises toward the surface. Boiling wells at Bridge, Idaho are near the intersection of north-northeast normal faults which have moved as recently as the late (?) Pleistocene, and an east-northeast structure, probably a right-lateral fault. Deep circulation of ground water in this region of relatively high heat flow and upwelling along faults is the probable cause of the thermal anomaly.

Idaho↗
USGS1978

Natural radioactivity in geothermal waters, Alhambra Hot Springs and nearby areas, Jefferson County, Montana

Radioactive hot springs issue from a fault zone in crystalline rock of the Boulder batholith at Alhambra, Jefferson County, in southwestern Montana. The discharge contains high concentrations of radon, and the gross alpha activity and the concentration of adium-226 exceed maximum levels recommended by the Environmental Protection Agency for drinking water. Part of the discharge is diverted for space heating, bathing, and domestic use. The radioactive thermal waters at measured temperatures of about 60°C are of the sodium bicarbonate type and saturated with respect to calcium carbonate. Radium-226 in the rock and on fractured surfaces or coprecipitated with calcium carbonate probably is the principal source of radon that is dissolved in the thermal water and discharged with other gases from some wells and springs. Local surface water and shallow ground water are of the calcium bicarbonate type and exhibit low background activity. The temperature, percent sodium, and radioactivity of mixed waters adjacent to the fault zone increase with depth. Samples from most of the major hot springs in southwestern Montana have been analyzed for gross alpha and beta activity. The high level of radioactivity at Alhambra appears to be related to leaching of radioactive material from siliceous veins by ascending thermal waters and is not a normal characteristic of hot springs issuing from fractured crystalline rock in Montana.

Montana↗