Newberry Volcano Research Articles

Plinian eruptions at Glacier Peak and Newberry volcanoes, United States: Implications for volcanic hazards in the Cascade Range

Several fall deposits from Glacier Peak and Newberry volcanoes, both located in the Cascade Range, United States, have been studied to determine eruptive column heights, intensities, and volumes. The late Pleistocene eruptions of Glacier Peak ranged from small phreatic explosions to two Plinian eruptions that each erupted more than 1 km 3 of magma at intensities >10 8 kg/s, generating plumes with heights >30 km. At Newberry volcano, the last Plinian eruption (ca. 1300 14 C yr B.P.) had an intensity of 2.8 × 10 7 kg/s and a plume height of 18 to 21 km. About 0.1 km 3 of magma was erupted in the Plinian phase, followed by eruption of a pyroclastic flow and an obsidian lava flow. Combined with similar data from Mount St. Helens, Mount Rainier, and Mount Mazama (Crater Lake), these eruptions define the range of Plinian events that have occurred in the Cascade volcanic arc in the past 12 k.y. During this period there have been Plinian eruptions with plume heights between 11 and 55 km, intensities between 10 6 and 10 9 kg/s, and volumes between 0.01 and >5 km 3 of magma. All eruptions with intensities greater than or equal to 10 8 kg/s also produced large-volume pyroclastic flows and surges. Monitoring column height (intensity) during eruptions could help mitigate hazards because it may indicate pending generation of pyroclastic flows. In the Cascade Range, there have been at least 12 eruptions of >1 km 3 of tephra in the past 12 k.y., suggesting that eruptions of such magnitude occur about once every 1 k.y., although such frequencies vary greatly at each volcano. The volume of magma erupted in each event correlates with both column height (intensity) and magma composition, suggesting that eruptions of these volcanoes relate to the accumulation rate of magma in their reservoirs.

Active high‐resolution compressional wave attenuation tomography at Newberry Volcano, Central Cascade Range

In this study, we use the seismic data from a previous study at Newberry to compute its three‐dimensional compressional wave attenuation structure. The data consist of eight explosions recorded on an array of about 120 seismograph stations. The shots are located on two concentric circles centered on the caldera with radii of 39 and 85 km. Attenuation is estimated using spectral ratios to compute δt* at each station for each shot. The data are inverted using a least squares technique. Our results indicate that regions of inferred boiling water (i.e., two‐phase pore fluid) are correlated spatially with regions of high attenuation not corresponding to low velocities. Two regions are of particular interest. One is underneath the Newberry II drill hole, in the central part of the caldera, where results from a flow test suggest that two‐phase fluid conditions existed in the bottom of the hole before the flow test. The other region is beneath the west flank of the volcano, which has been interpreted as an attractive geothermal prospect because of a shallow conductive anomaly. Our results are consistent with the suggestion made in an earlier paper by us that two‐phase geothermal reservoirs can be located within complex three‐dimensional structures by using jointly interpreted compressional wave velocity and attenuation images.

Experimental evidence of resistivity frequency-dispersion in magnetotellurics in the Newberry (Oregon), Snake River Plain (Idaho) and Campi Flegrei (Italy) volcano-geothermal areas

We show that magnetotelluric measurements carried out in volcano-geothermal areas can be significantly affected by the resistivity frequency-dispersion phenomenon. The polarization effects are recognized by comparing magnetotelluric and DC geoelectrical deep soundings performed in the same station. Indeed, the conventional separate analysis of the two data sets sometimes gives unconformable results, especially as it regards the resistivity and thickness of the conductive layers, ascribable to the geothermal fluid-filled rocks. These apparent discrepancies can be overcome by admitting the occurrence of intense induced polarization effects inside the rocks having extensive alterations due to hydrothermal paragenesis. The basic theory of the induced polarization effects over magnetotelluric measurements is at first briefly recalled. Then, three impressive field examples taken from previous experiments performed in the Newberry Volcano, Snake River Plain and Campi Flegrei geothermal areas are presented and discussed.

Magmatic inclusions in the Holocene rhyolites of Newberry Volcano, central Oregon

The 1350 years B.P. Big Obsidian Flow (BOF) at Newberry Volcano in central Oregon contains a wide variety of mafic magmatic inclusions. Although little grain size variation is observed within single inclusions, within the suite textures vary continuously from fine‐grained (“quench”) to coarse‐grained (“cumulate”). The BOF inclusion suite, therefore, defies conventional genetic classifications. Detailed petrographic and geochemical observations require a new model for inclusion formation. Only a few of the finer‐grained inclusions have margins suggestive of liquid‐liquid interaction. Interstitial glass content (≈ 20 vol %) and composition (high‐silica rhyolite) are approximately constant throughout the suite. Mineral compositional zoning is greater in the coarse‐grained than fine‐grained inclusions. Whole inclusion compositions vary significantly but do not correlate well with textural diversity. We interpret the BOF inclusion suite to be a heterogeneous sample set of whole inclusions and parts of disaggregated inclusions. The compositional variability of the suite can be explained by a combination of preentrapment (hybridization) and postentrapment (interstitial liquid loss/gain) processes. Preentrapment hybridization involved mixing of basaltic andesite magma similar to Holocene flank flows and up to 30% rhyolitic liquid. The BOF inclusions may demonstrate the recent existence of mafic magma in the Newberry system. Inclusion features characteristic of small ΔT are consistent with the crystal‐free nature of the BOF, suggesting that the rhyolite may have been superheated. If true, a crystal fractionation origin for the BOF rhyolite is unlikely. The disaggregation of grain size and compositionally zoned inclusions, which produced the observed textural diversity in the BOF suite, compounds problems of interpreting mafic inclusions in silicic volcanic rocks and, more so, in plutonic equivalents.

Crustal structure of east central Oregon: Relation between Newberry Volcano and regional crustal structure

A 180‐km‐long seismic refraction transect from the eastern High Cascades, across Newberry Volcano, to the eastern High Lava Plains is used to investigate the subvolcanic crustal and upper mantle velocity structure there. Near‐surface volcanic flows and sedimentary debris (1.6–4.7 km/s), ranging from 3 to 5 km in thickness, overlie subvolcanic Basin and Range structures. East and west of Newberry Volcano, the subvolcanic basement (5.6 km/s) has been downwarped, producing 5‐km‐deep basins. The midcrust (8‐ to 28‐km depth) is characterized by velocities ranging from 6.1 to 6.5 km/s and varies laterally in thicknesses. The lower crust is characterized by art unusually high velocity (about 7.4 km/s), and its geometry mirrors the subvolcanic basement geometry. The Moho is located at a depth of 37 km and represents a transition to an upper mantle velocity of 8.1 km/s. The shallow subsurface (1.2 km) beneath Newberry Volcano is characterized by high‐velocity (5.6 km/s, versus 4.1 km/s for the surrounding area) intrusions and appears to be located on a basement high. Beneath the seismic refraction array at Newberry Volcano, an absence of low‐velocity anomalies suggests that large silicic magma chambers do not exist in the upper crust, but apparent high attenuation of the seismic wave field may be consistent with either partial melts in small volumes, elevated crustal temperatures, and/or poor geophonerecording site coupling. The east central Oregon velocity structure is nearly identical to that of the northwestern Nevada Basin and Range and the Modoc Plateau of northeastern California, and variations in the deep crustal structure about Newberry Volcano are consistent with tectonism involving crustal underplating, melting, and extension. If paleomagnetic estimates of extension in the east central Oregon area are correct, the North American continent experienced significant growth through extension, underplating, and volcanism in east central Oregon. Comparison of east central Oregon with other continental back arc areas shows similarities in crustal thickness, velocity, and heat flow.

High‐resolution seismic tomography of compressional wave velocity structure at Newberry Volcano, Oregon Cascade Range

Compressional wave velocity structure is determined for the upper crust beneath Newberry Volcano, central Oregon, using a high‐resolution active‐source seismic‐tomography method. Newberry Volcano is a bimodal shield volcano east of the axis of the Cascade Range. It is associated both with the Cascade Range and with northwest migrating silicic volcanism in southeast Oregon. High‐frequency (∼7 Hz) crustal phases, nominally Pg and a midcrustal reflected phase, travel upward through a target volume beneath Newberry Volcano to a dense array of 120 seismographs. This arrangement is limited by station spacing to 1‐ to 2‐km resolution in the upper 5 to 6 km of the crust beneath the volcano's summit caldera. The experiment tests the hypothesis that Cascade Range volcanoes are underlain only by small magma chambers. A small low‐velocity anomaly delineated about 3 km below the summit caldera supports this hypothesis for Newberry Volcano and is interpreted as a possible magma chamber of a few to a few tens of km3 in volume. A ring shaped high‐velocity anomaly nearer the surface coincides with the inner mapped ring fractures of the caldera. It also coincides with a circular gravity high, and we interpret it as largely subsolidus silicic cone sheets. The presence of this anomaly and of silicic vents along the ring fractures suggests that the fractures are a likely eruption path between the small magma chamber and the surface.

Overview of the structure and geothermal potential of Newberry Volcano, Oregon

Evidence from a broad range of geological and geophysical investigations of Newberry Volcano in central Oregon suggests the presence of a small magma body beneath the summit caldera. Drilling has encountered temperatures indicative of a hydrothermal system above the hypothesized magma body. On the basis of hydrothermal mineralogy the temperature of the hydrothermal system is at or near its maximum value, indicating that the hydrothermal system is young. Basaltic underplating is postulated to replenish the magma body. The results of interdisciplinary studies at Newberry Volcano document that young, silicic volcanism in the Cascade Range can have geothermal potential. These results should be applied with caution to the rest of the Cascade Range because of the strong influence of Basin and Range extensional tectonics on Newberry Volcano's style of volcanism.

The hydrothermal system at Newberry Volcano, Oregon

Results of recent geological and geophysical studies at Newberry Volcano have been incorporated into conceptual and numerical models of a magma‐based hydrothermal system. Numerical simulations begin with emplacement of a small magma body, the presumed source of silicic eruptions at Newberry that began about 10,000 B.P., into a thermal regime representing 100,000 years of cooling of a large underlying intrusion. Simulated flow patterns and thermal histories for three sets of hypothetical permeability values are compatible with data from four geothermal drill holes on the volcano. Meteoric recharge cools the caldera‐fill deposits, but thermal water moving up a central conduit representing a permeable volcanic vent produces temperatures close to those observed in drill holes within the caldera. Meteoric recharge from the caldera moves down the flanks and creates a near‐isothermal zone that extends several hundred meters below the water table, producing temperature profiles similar to those observed in drill holes on the flanks. The temperatures observed in drill holes on the flanks are not influenced by the postulated Holocene magma body. The elevated temperature gradients measured in the lower portions of these holes may be related to the cumulative effect of older intrusions. The models also indicate that meteoric recharge to the deep hydrothermal system probably originates within or near the caldera. Relatively low fluid velocities at depth suggest that at least a significant fraction of the thermal fluid may be very old.

Three‐dimensional P velocity structure of the crust below Newberry Volcano, Oregon

Utilizing teleseismic P residuals, we have detected a column of high P velocity material extending from within 10 km of the surface below the summit of Newberry Volcano, Oregon, to midcrustal depths near 25 km. We interpret this column to be the expression of a swarm of predominantly subsolidus gabbroic sills and dikes which were intruded as the volcano was built. The high P velocities observed below the volcano severely limit the size of magma chambers which could presently exist in the crust below Newberry Volcano. Those possible include a few percent of partial melt distributed through large volumes of a mafic intrusion zone in the midcrust; a few, smaller, higher melt fraction zones in the midcrust with dimensions less than 6 km and whose aggregate volume is only a few percent of enclosing volumes of 200 km3; small magma bodies with dimensions of a few kilometers located within the upper 10 km of the crust; or a mafic, crystal‐rich magma of arbitrary dimensions located in the upper few km. The low P velocities detected in the upper 4 km beneath the center of the summit caldera may be partially caused by a magma chamber in the second of these catagories.

Gravity model studies of Newberry Volcano, Oregon

Newberry Volcano, a large Quaternary volcano located about 60 km east of the axis of the High Cascades volcanoes in central Oregon, has a coincident positive residual gravity anomaly of about 12 mGals. Model calculations of the gravity anomaly field suggest that the volcano is underlain by an intrusive complex of mafic composition of about 20‐km diameter and 2‐km thickness, at depths above 4 km below sea level. However, uplifted basement in a northwest trending ridge may form part of the underlying excess mass, thus reducing the volume of the subvolcanic intrusive. A ring dike of mafic composition is inferred to intrude to near‐surface levels along the caldera ring fractures, and low‐density fill of the caldera floor probably has a thickness of 0.7–0.9 km. The gravity anomaly attributable to the volcano is reduced to the east across a north‐northwest trending gravity anomaly gradient through Newberry caldera and suggests that normal, perhaps extensional, faulting has occurred subsequent to caldera formation and may have controlled the location of some late‐stage basaltic and rhyolitic eruptions. Significant amounts of felsic intrusive material may exist above the mafic intrusive zone but cannot be resolved by the gravity data.

Core hole drilling and the “rain curtain” phenomenon at Newberry Volcano, Oregon

Two core holes have been completed on the flanks of Newberry Volcano, Oregon. Core hole GEO N‐1 has a heat flow of 180 mW m−2, reflecting subsurface temperatures, sufficient for commercial exploitation of geothermally generated electricity. GEO N‐3, which has a heat flow of 86 mW m−2, is less encouraging. We emphasize the “rain curtain” effect with the hope that a detailed discussion of this phenomenon at two distinct localities will lead to a better understanding of the physical processes in operation. Core hole GEO N‐1 was cored to a depth of 1387 m at a site located 9.3 km south of the center of the volcano. Core hole GEO N‐3 was cored to a depth of 1220 m at a site located 12.6 km north of the center of the volcano. Both core holes penetrated interbedded pyroclastic lava flows and lithic tuffs ranging in composition from basalt to rhyolite, basaltic andésite being the most common rock type. Potassium‐argon age dates range up to 2 Ma. Caving and sloughing were encountered in both core holes at depths near the regional water table. Both core holes penetrate three distinct thermal regimes. The uppermost regime is isothermal at mean air temperature down to about 900–1000 m (the rain curtain). A thermally conductive regime exists near the bottom of each core hole. Separating these two thermal regimes is a transition zone exhibiting considerable hydrologic disturbance. The uppermost isothermal regime is characterized by (1) a low and fairly uniform response on the gamma ray log (N‐1, N‐3) and the electrical conductivity log (N‐1), (2) temperatures below surface ambient measured downhole with a maximum recording thermometer (MRT) during periodic pauses in drilling operations (N‐1, N‐3), and (3) drilling fluids whose chemistry does not reflect an influx of geothermal fluids (N‐3). In contrast, the thermally conductive regime is characterized by (1) a high and variable response on the gamma ray log (N‐1, N‐3) and on the electrical conductivity log (N‐1), (2) temperatures (MRT) measured downhole during pauses in drilling which are above ambient and which track in situ conditions (N‐1, N‐3) and (3) drilling fluids whose chemistry clearly reveals a geothermal component (N‐3). The transition zone is characterized by major washouts in the caliper log (N‐1, N‐3), a major anomaly in the mercury content of the rocks (N‐1), an extremely strong response on the gamma ray log (N‐1, N‐3) and electrical conductivity log (N‐1), and a major self‐potential anomaly (N‐1). Smectite alteration, which seems to control the results of surface geoelectrical studies, begins in the isothermal regime close to and perhaps associated with the regional water table.

Geologic evidence for a magma chamber beneath Newberry Volcano, Oregon

At Newberry Volcano, central Oregon, more than 0.5 m.y. of magmatic activity, including caldera collapse and renewed caldera‐filling volcanism, has created a structural and thermal chimney that channels magma ascent. Holocene rhyolitic eruptions (1) have been confined mainly within the caldera in an area 5 km in diameter, (2) have been very similar in chemical composition, phenocryst mineralogy, and eruptive style, and (3) have occurred as recently as 1300 years ago, with repose periods of 2000–3000 years between eruptions. Holocene basaltic andesite eruptions are widespread on the flanks but are excluded from the area of rhyolitic volcanism. Basaltic andesite in fissures at the edge of the rhyolite area has silicic inclusions and shows mixed basalt‐rhyolite magma relations. These geologic relations and the high geothermal gradient that characterizes the lower part of a drill hole in the caldera (U.S. Geological Survey Newberry 2) indicate that a rhyolitic magma chamber has existed beneath the caldera throughout the Holocene. Its longevity probably is a result of intermittent underplating by basaltic magma.

Electrical structure of Newberry Volcano, Oregon

From the interpretation of magnetotelluric, transient electromagnetic, and Schlumberger resistivity soundings, the electrical structure of Newberry Volcano in central Oregon is found to consist of four units. From the surface downward, the geoelectrical units are (1) very resistive, young, unaltered volcanic rock, (2) a conductive layer of older volcanic material composed of altered tuffs, (3) a thick resistive layer thought to be in part intrusive rocks, and (4) a lower‐crustal conductor. This model is similar to the regional geoelectrical structure found throughout the Cascade Range. Inside the caldera, the conductive second layer corresponds to the steep temperature gradient and alteration minerals observed in the USGS Newberry 2 test hole. Drill hole information on the south and north flanks of the volcano (test holes GEO N‐1 and GEO N‐3, respectively) indicates that outside the caldera the conductor is due to alteration minerals (primarily smectite) and not high‐temperature pore fluids. On the flanks of Newberry the conductor is generally deeper than inside the caldera, and it deepens with distance from the summit. A notable exception to this pattern is seen just west of the caldera rim, where the conductive zone is shallower than at other flank locations. The volcano sits atop a rise in the resistive layer, interpreted to be due to intrusive rocks. The intrusive material has served as a heat source to produce enhanced hydrothermal alteration and, perhaps in the case of the west‐flank anomaly, elevated fluid temperatures. While no public drill hole information is available to confirm this hypothesis, the west‐flank anomaly appears to be a good geothermal target. In addition to the possibility that a region on the west side of the volcano could be favorable for prospecting, part of the resistive structure under the center of the volcano could be due to a vapor‐dominated environment with temperatures above 300°C. In other parts of the Cascades, pervasive alteration has produced mixed layer clays and zeolites, resulting in low‐resistivity anomalies. Low resistivities cannot be assumed to indicate high‐temperature pore fluids. The use of electrical methods that measure resistivity as a function of excitation frequency, such as spectral induced polarization, may provide a way of obtaining information about the type and extent of alteration.

Petrology and hydrothermal mineralogy of U.S. geological survey Newberry: 2. Drill core from Newberry Caldera, Oregon

U.S. Geological Survey Newberry 2 was drilled to a depth of 932 m within Newberry caldera. The bottom‐hole temperature of 265°C is the highest reported temperature of any drill hole in the Cascades region of the United States. The upper part of the stratigraphic section penetrated by Newberry 2 consists of caldera fill below which are increasingly more mafic lavas ranging from rhyodacite at 501 m to basalt at 932 m. Measured temperatures shallower than 300 m are less than 35°C, and rock alteration consists of hydration of glass and local palagonitization of basaltic tuffs. Incipient zeolitization and partial smectite replacement of ash and pumice occurred throughout the pumiceous lithic tuffs from 300 to 500 m. Higher‐temperature alteration of the tuffs to chlorite and mordenite occurs adjacent to a rhyodacite sill at 460–470 m; alteration minerals within the sill consist of pyrrhotite, pyrite, quartz, calcite, and siderite. Below 697 m the rocks are progressively more altered with depth mainly because of increased temperature along a conductive gradient from 100°C at 697 m to 265°C at 930 m. Fluid inclusions in quartz and calcite indicate that temperatures in the past have been higher than at present, most likely due to local confining pressures between impermeable lava flows. Flow breccias are more altered than the adjacent dense massive lava flows, regardless of composition, because of their much higher permeability. Hydrothermal minerals in this zone are mainly mixed‐layer chlorite‐smectite, quartz, calcite, and pyrite. Chlorite becomes more abundant than mixed‐layer clays near the bottom of the hole. In the lowest two lava flows, epidote, anhydrite, and scarce hematite occur locally. Alteration and leaching in the basal 2 m are unique and have led to the postulation of a localized two‐phase fluid zone consisting mainly of steam and CO2. The hydrothermal system of Newberry 2 is a simple evolving system associated with the evolution of Newberry Volcano. Only a few localized highly altered intervals where fracturing controlled fluid access occur in the core. There are no crosscutting fractures to indicate multiple hydrothermal systems. Chemical analyses of altered rocks and equivalent fresh rocks indicate that little chemical migration has taken place.

Isotope geochemistry of minerals and fluids from Newberry volcano, Oregon

Isotopic compositions were determined for hydrothermal quartz, calcite, and siderite from core samples of the Newberry 2 drill hole, Oregon. The δ15O values for these minerals decrease with increasing temperatures. The values indicate that these hydrothermal minerals precipitated in isotopic equilibrium with water currently present in the reservoirs. The δ18O values of quartz and calcite from the andesite and basalt flows (700–932 m) have isotopic values which require that the equilibrated water δ18O values increase slightly (− 11.3 to −9.2‰) with increasing measured temperatures (150–265°C). The lithic tuffs and brecciated lava flows (300–700 m) contain widespread siderite. Calculated oxygen isotopic compositions of waters in equilibrium with siderite generally increase with increasing temperatures (76–100°C). The δ18O values of siderite probably result from precipitation in water produced by mixing various amounts of the deep hydrothermal water (− 10.5 ‰) with meteoric water (− 15.5 ‰) recharged within the caldera. The δ13C values of calcite and siderite decrease with increasing temperatures and show that these minerals precipitated in isotopic equilibrium with CO2 of about −8 ‰. The δ18O values of weakly altered (<5% alteration of plagioclase) whole-rock samples decrease with increasing temperatures above 100°C, indicating that exchange between water and rock is kinetically controlled. The water/rock mass ratios decrease with decreasing temperatures. The δ18O values of rocks from the bottom of Newberry 2 show about 40% isotopic exchange with the reservoir water. The calculated δ18O and δD values of bottom hole water determined from the fluid produced during the 20 hour flow test are −10.2 and −109‰, respectively. The δD value of the hydrothermal water indicates recharge from outside the caldera.

Geothermal drilling in the Cascade Range: Preliminary results from a 1387‐m core hole, Newberry Volcano, Oregon

The Cascade Mountain Range, which consists of a series of Quaternary and late Tertiary andesitic volcanos that extend from Northern California to Southern British Columbia, is a geologic province with immense potential for the generation of electricity from geothermal energy resources. The geothermal potential for the Cascades Province may well be thousands if not tens of thousands of megawatts [see Bloomquist et al., 1985]. Yet to date there are no geothermal power plants operating in the Cascades Province, and none are planned. Furthermore, except for the obvious heat sources represented by the active volcanos, very little is known about the geothermal resources in the Cascades.

Oregon Seismic Experiment

The United States Geological Survey (USGS), with support from the Geothermal and Hydropower Technologies Division of the U.S. Department of Energy, will be conducting an active seismic experiment in central Oregon using nine large explosions during the last week of August 1984. A major goal of this experiment is to detect kilometersize magma chambers in the upper crust below Newberry Volcano (Figure 1). The planned experiment is a small‐scale version of one type of seismic‐imaging experiment proposed by the Program for Array Seismic Studies of the Continental Lithosphere (PASSCL). Because of the required density of the recording array, the USGS recording effort will be concentrated in and around the summit caldera and leave ample opportunity for additional recording of the large shots, by interested parties, to study the rest of the volcano and surrounding geologic provinces.

Oil and Gas Developments in West Coast Area in 1981

The total exploratory footage and number of wells drilled in the onshore area of California during 1981 increased approximately 10% and 20%, respectively, over the 1980 figures. Both the average footage drilled per well (5,579 ft) and the percentage of success (32.7%) showed declines from 1980. Eight wildcats established new fields in 1981. Two of the wildcats discovered new oil fields and 6 found new gas fields. An additional gas find has been treated as a discovery because of its stratigraphic significance. Onshore development drilling included 2,078 wells; 97% of these were completed as successful producers, the same percentage as in 1980. For the California offshore, just 5 exploratory well completions were reported to the Committee on Statistics of Drilling in 1981; only 2 were successful. Texaco announced its Pitas Point gas field extension in May, and Chevron announced a new oil field discovery, the Point Arguello, in October. There were 118 development wells drilled, of which 99 (83.9%) were successful. Development footage and number of wells were up, but the percentage of success declined from 90% in 1980. California's oil production reached an all-time high of 384.8 million bbl in 1981. The state's previous record, set in 1968, was 375.4 million bbl. Geothermal activity in California centered on development of the proven Imperial Valley and Geysers areas and the discovery of the Coso area in Inyo County. Activity in Oregon included evaluation of the Mount Hood and Newberry Volcano areas. Oil and gas exploratory drilling in Oregon during 1981 led to the discovery of a new gas field by American Quasar in Linn County and to the establishment of a new gas pool by Reichhold Energy at the Mist field in Columbia County. The major portion of Washington's exploratory drilling in 1981 was carried out by Shell in Kittitas County in the south-central part of the state. At last report, the hydrocarbon accumulations found had been deemed noncommercial.

Hottest Oregon geothermal find

A geothermal test hole drilled 810 m into the summit crater of Newberry Volcano in Oregon measured 190°C, the hottest temperature measured so far in an Oregon geothermal energy prospect. What's more, a high temperature gradient discovered in the lower sixth of the test hole may point to greater potential than was previously thought for geothermal energy in the Cascade Range.Scientists from the U.S. Geological Survey found that in the hole's lower 140 m the temperature rose at a rate equivalent to about 600°C per kilometer. The worldwide continental average is about 30°C per kilometer. Edward Sammel, a USGS hydrologist, is the leader of the geothermal drilling project at Newberry. David Blackwell of the Southern Methodist University made the temperature measurements in the hole.

Pacific Northwest meeting

The Twenty‐Sixth Annual Meeting of Pacific Northwest AGU was held in Bend, Oregon, September 17–18, 1979, attracting 101 papers and approximately 400 participants. A special symposium on volcanism included five topical sessions: Large Explosive Eruptions, Volatiles in Volcanism, Rates of Magma Supply and Ages of Volcanic Systems, Magma Mixing, and Glacier‐Volcano Interactions. Prior to and following formal sessions, field trips were taken to Columbia River Basalt‐Clarno and John Day formations (Swanson, Wright, Robinson); Medicine Lake Highlands (Donnelly‐Nolan, Eichelberger, Heiken, Fink); Newberry Volcano (Macleod, Chitwood, Sherrod); High Cascades (Ed Taylor); Christmas Lake Valley (Heiken, Fisher); Brothers Fault Zone‐Harney Basin (Walker, Nolf). Session summaries follow.