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USGS2009

Thermodynamic model for uplift and deflation episodes (bradyseism) associated with magmatic-hydrothermal activity at the Campi Flegrei (Italy)

Campi Flegrei (CF) is a large volcanic complex located west of the city of Naples, Italy. Repeated episodes of bradyseism (slow vertical ground movement) near the town of Pozzuoli have been documented since Roman times. Bradyseismic events are interpreted as the consequence of aqueous fluid exsolution during magma solidification on a slow timescale (10 3 –10 4 yr) superimposed upon a shorter (1–10 yr) timescale for the episodic expulsion of fluid from a deep (~ 3–5 km) lithostatically-pressured low-permeability reservoir to an overlying hydrostatic reservoir. Cycles of inflation and deflation occur during short duration transient events when connectivity is established between deep and shallow hydrothermal reservoirs. The total seismic energy released (4 × 10 13 J) during the 1983–1984 bradyseismic crisis is consistent with the observed volume change (uplift) and consistent with the notion that seismic failure occurs in response to the shear stress release induced by volume change. Fluid transport and concomitant propagation of hydrofractures as fluid expands from lithostatic to hydrostatic pressure during decompression leads to ground surface displacement. Fluid decompression occurs along the fluid isenthalp (Joule–Thompson expansion) during transient periods of reservoir connectivity and leads to mineral precipitation. Each kilogram of fluid precipitates about 3 × 10 − 3 kg of silica along a typical decompression path along the isenthalp. Mineral precipitation modifies the permeability and acts to reseal connection paths thereby isolating lithostatic and hydrostatic reservoirs ending one bradyseism phase and beginning another. Crystallization and exsolution of the magmatic fluid generates ≈ 7 × 10 15 J of mechanical ( P Δ V ) energy, and this is sufficient to accomplish the observed uplift at CF. Although magma emplacement is the ultimate origin of bradyseism, fresh recharge of magma is not a prerequisite. Instead, short to intermediate timescale phenomena associated with fluid decompression and expansion in the crust with large variations in permeability, including permeability anisotropy, are the key elements at CF.

Naples↗

USGS2011

International heat flow commission celebrates 40 years

The outflow of heat from the Earth's interior is, in terms of energy, the most impressive terrestrial phenomenon. Its present rate of about 1021 joules per year is order‐of‐magnitudes greater than the energy dissipation of earthquakes or heat loss from volcanic eruptions. The study of the Earth's internal heat plays an important role in understanding the Earth's origin, internal constitution, and plate tectonics. The thermal structure of the Earth, generally referred to as the geothermics, or also as the (terrestrial) heat flow, has been studied for a long time. However, modern geothermics, one of the fundamental geophysical disciplines, is relatively young. The International Heat Flow Commission (IHFC), under which the academic geothermal research on the international scale is organized, was created only in 1963. The IHFC, operating under the International Association of Seismology and Physics of the Earth's Interior (IASPEI), covers a broad scope of geophysical studies, and links the activities of other associations of the International Union of Geodesy and Geophysics (IUGG).

Eos, Earth and Space Science News↗

USGS2002

Predation on exotic zebra mussels by native fishes: Effects on predator and prey

1. Exotic zebra mussels, Dreissena polymorpha, occur in southern U.S. waterways in high densities, but little is known about the interaction between native fish predators and zebra mussels. Previous studies have suggested that exotic zebra mussels are low profitability prey items and native vertebrate predators are unlikely to reduce zebra mussel densities. We tested these hypotheses by observing prey use of fishes, determining energy content of primary prey species of fishes, and conducting predator exclusion experiments in Lake Dardanelle, Arkansas. 2. Zebra mussels were the primary prey eaten by 52.9% of blue catfish, Ictalurus furcatus; 48.2% of freshwater drum, Aplodinotus grunniens; and 100% of adult redear sunfish, Lepomis microlophus. Blue catfish showed distinct seasonal prey shifts, feeding on zebra mussels in summer and shad, Dorosoma spp., during winter. Energy content (joules g-1) of blue catfish prey (threadfin shad, Dorosoma petenense; gizzard shad, D. cepedianum; zebra mussels; and asiatic clams, Corbicula fluminea) showed a significant species by season interaction, but shad were always significantly greater in energy content than bivalves examined as either ash-free dry mass or whole organism dry mass. Fish predators significantly reduced densities of large zebra mussels (>5 mm length) colonising clay tiles in the summers of 1997 and 1998, but predation effects on small zebra mussels (???5 mm length) were less clear. 3. Freshwater drum and redear sunfish process bivalve prey by crushing shells and obtain low amounts of higher-energy food (only the flesh), whereas blue catfish lack a shell-crushing apparatus and ingest large amounts of low-energy food per unit time (bivalves with their shells). Blue catfish appeared to select the abundant zebra mussel over the more energetically rich shad during summer, then shifted to shad during winter when shad experienced temperature-dependent stress and mortality. Native fish predators can suppress adult zebra mussel colonisation, but are ultimately unlikely to limit population density because of zebra mussel reproductive potential.

Freshwater Biology↗

USGS1981

The Lake Bosumtwi impact crater, Ghana

The 1-m.y.-old Bosumtwi Crater, Ghana, has a nearly circular shape with a rim diameter of 11 km north-south and 10 km east-west. It is surrounded by a circular depression and an outer ridge of diameter 20 km. Polymict breccias averaging at least 20 m thick with clasts as much as 5 m long occur on the outer ridge, and the crater rim shows in situ shattered rock. Patches of suevite have been found in the circular depression north and south of the crater. Analogy with better-known craters suggests that Bosumtwi has a central uplift rising to 200 m beneath the lake floor. An aeromagnetic anomaly of amplitude 50 nanotesla (nT) over the northern half of the lake is interpreted as due to a layer of magnetized fallback breccia beneath the lake sediments. The normal polarity of the breccia shows that the crater was formed during the normal Jaramillo event of 0.97 to 0.85 m.y. ago, which agrees with the magnetic stratigraphy of the related Ivory Coast microtektites. A regional gravity survey indicates a negative Bouguer anomaly over the crater. There is some geochemical evidence that the meteorite was an iron, and its mass and energy are suggested as about 10 8 tons and 3 × 10 19 joules or 7.3 × 10 3 megatons.

Lake Bosumtwi↗

USGS1988

The formation and failure of natural dams

Of the numerous kinds of dams that form by natural processes, dams formed from landslides, glacial ice, and late-neoglacial moraines present the greatest threat to people and property. Landslide dams form in a wide range of physiographic settings. The most common types of mass movements that form landslide dams are rock and debris avalanches; rock and soil slumps and slides; and mud, debris, and earth flows. The most common initiation mechanisms for dam-forming landslides are excessive rainfall and snowmelt and earthquakes. Landslide dams can be classified into six categories based on their relation with the valley floor. Type I dams (11% of 184 landslide dams from around the world that we were able to classify) do not reach from one valley side to the other. Type II dams (44%) span the entire valley floor, in some cases depositing material high on opposite valley sides. Type III dams (41%) move considerable distances both upstream and downstream from the landslide failure. Type IV dams (<1%) are rare and involve the contemporaneous failure of material from both sides of a valley. Type V dams (<1%) also are rare and are created when a single landslide sends multiple tongues of debris into a valley and forms two or more landslide dams in the same reach of river. Type VI dams (3%) involve one or more failure surfaces that extend under the stream or valley and emerge on the opposite valley side. Many landslide dams fail shortly after formation. In our sample of 73 documented landslide-dam failures, 27% of the landslide dams failed less than 1 day after formation, and about 50% failed within 10 days. Over-topping is by far the most common cause of failure. The timing of failure and the magnitude of the resulting floods are controlled by dam size and geometry; material characteristics of the blockage; rate of inflow to the impoundment; size and depth of the impoundment; bedrock control of flow; and engineering controls such as artificial spill-ways, diversions, tunnels, and planned breaching by blasting or conventional excavation. Glacial-ice dams can produce at least nine kinds of ice-dammed lakes. The most dangerous are lakes formed in main valleys dammed by tributary glaciers. Failure can occur by erosion of a drainage tunnel under or through the ice dam or by a channel over the ice dam. Cold polar-ice dams generally drain supraglacially or marginally by downmelting of an outlet channel. Warmer, temperate-ice dams tend to fail by sudden englacial or subglacial breaching and drainage. Late-neoglacial moraine-dammed lakes are located in steep mountain areas affected by the advances and retreats of valley glaciers in the last several centuries. These late-neoglacial dams pose hazards because (1) they are sufficiently young that vegetation has not stabilized their slopes, (2) many dam faces are steeper than the angle of repose, (3) these dams and lakes are immediately downslope from steep crevassed glaciers and near-vertical rock slopes, and (4) downstream from these dams are steep canyons with easily erodible materials that can be incorporated in the flow and increase flood peaks. The most common reported failure mechanism is overtopping and breaching by a wave or series of waves in the lake generated by icefalls, rockfalls, or snow or rock avalanches. Melting of ice cores or frozen ground and piping and seepage are other possible failure mechanisms. Natural dams may cause upstream flooding as the lake rises and downstream flooding as a result of failure of the dam. Although data are few, for the same potential energy at the dam site, ownstream flood peaks from the failure of glacier-ice dams are smaller than those from landslide, moraine, and structed earth-fill and rock-fill dam failures. Moraine-dam failures appear to produce some of the largest downstream flood peaks for potential energy at the dam site greater than 10 11 -10 12 joules. Differences in flood peaks natural-dam failures appear to be controlled by dam characteristics and failure mechanisms.

Geological Society of America Bulletin↗

USGS1983

Geothermal resources of southern Idaho

The geothermal resource of southern Idaho as assessed by the U.S. Geological Survey in 1978 is large. Most of the known hydrothermal systems in southern Idaho have calculated reservoir temperatures of less than 150?C. Water from many of these systems is valuable for direct heat applications, but is lower than the temperature of interest for commercial generation of electricity at the present time. Most of the known and inferred geothermal resources of southern Idaho underlie the Snake River Plain. However, major uncertainties exist concerning the geology and temperatures beneath the plain. By far the largest hydrothermal system in Idaho is in the Bruneau-Grand View area of the western Snake River Plain with a calculated reservoir temperature of 107?C and an energy of 4.5? 10 20 joules. No evidence of higher temperature water associated with this system has been found. Although the geology of the eastern Snake River Plain suggests that a large thermal anomaly may underlie this area of the plain, direct evidence of high temperatures has not been found. Large volumes of water at temperatures between 90? and 150?C probably exist along the margins of the Snake River Plain and in local areas north and south of the plain. Areas that appear particularly promising for the occurrence of large high-temperature hydrothermal systems are: the area north of the Snake River Plain and west of the Idaho batholith, the Island Park area, segments of the margins of the eastern Snake River Plain, and the Blackfoot lava field.

Circular↗

USGS2009

Archive of digitized analog boomer and minisparker seismic reflection data collected from the Alabama-Mississippi-Louisiana Shelf during cruises onboard the R/V Carancahua and R/V Gyre, April and July, 1981

In April and July of 1981, the U.S. Geological Survey (USGS) conducted geophysical surveys to investigate the shallow geologic framework of the Alabama-Mississippi-Louisiana Shelf in the northern Gulf of Mexico. Work was conducted onboard the Texas A&M University R/V Carancahua and the R/V Gyre to develop a geologic understanding of the study area and to locate potential hazards related to offshore oil and gas production. While the R/V Carancahua only collected boomer data, the R/V Gyre used a 400-Joule minisparker, 3.5-kilohertz (kHz) subbottom profiler, 12-kHz precision depth recorder, and two air guns. The authors selected the minisparker data set because, unlike with the boomer data, it provided the most complete record. This report is part of a series to digitally archive the legacy analog data collected from the Mississippi-Alabama SHelf (MASH). The MASH data rescue project is a cooperative effort by the USGS and the Minerals Management Service (MMS). This report serves as an archive of high-resolution scanned Tagged Image File Format (TIFF) and Graphics Interchange Format (GIF) images of the original boomer and minisparker paper records, navigation files, trackline maps, Geographic Information System (GIS) files, cruise logs, and formal Federal Geographic Data Committee (FGDC) metadata.

Alabama, Louisiana, Mississippi↗

USGS1980

High-resolution seismic-reflection profiling data from the inner continental shelf of southeastern Massachusetts

Six hundred-seventy kilometers of closely spaced high-resolution seismic-reflection data have been collected from eastern Rhode Island Sound and Vineyard Sound, Mass, by the U.S. Geological Survey in cooperation with the Massachusetts Department of Public Works. These data were obtained during the June 1975 cruise of the R/V ASTERIAS as part of a continuing regional study of the Massachusetts offshore area to assess potential mineral resources, to evaluate environmental impact of mining of resources and of offshore disposal of solid waste and harbor dredge-spoil materials, and to map the offshore geology and shallow structure. The data were obtained by using a surface-towed EG&G Unit Pulse Boomer* (300 joules: 400 Hz-8kHz frequency) sound source. Reflected acoustic energy was detected by a 4.6-m, a-element hydrophone array, was amplified, was actively filtered (400 Hz-4kHz bandpass), and was graphically displayed on an EPC* dry paper recorder at a 0.25-second sweep rate. System resolution was generally 1 to 1.5 m. Navigational control was provided by Loran C (positional accuracy within 0.2 km) and was supplemented by radar and visual fixes. Positional information was logged at 15-minute intervals and at major course changes. The original records may be examined at the Data Library, U.S. Geological Survey, Woods Hole, MA 02543. Microfilm copies of the data are available for purchase from the National Geophysical and Solar-Terrestrial Data Center (NGSDC), Boulder, CO 80302.

Open-File Report↗

USGS1980

Single-channel seismic-reflection profiles from Massachusetts coastal waters and the western part of Georges Bank

The U.S. Geological Survey collected approximately 1,200 km each of airgun and minisparker single-channel seismic-reflection profiles during the R/V FAY cruise 023 in September 1976. The purpose of the 6-day cruise was to study the shallow sedimentary structure south and east of southern Massachusetts and to obtain magnetic and gravity data in these areas and in the vicinity of Great South Channel and Cape Ann. The survey was conducted by the U.S. Geological Survey as part of the Massachusetts Cooperative Marine Geologic Program. Seismic instruments used include a 1 Teledyne 600-joule minisparker system and a 20-in 3 airgun system. Navigational data during the cruise were obtained by the use of an Integrated Navigation System, which included the following subsystems: Teledyne Loran-C for both range-range and hyperbofic positions; Magnovox s'atellite receiver; Sperry Mark-29 gyrocompass; and Hewlett-Packard 21 MX computer system with dual 9-track magnetic tape recording. The original records may be studied at the U.S. Geological Survey offices in Woods Hole, Mass. Copies of the records can be purchased only from the National Geophysical and Solar-Terrestrial Data Center, NOAA/EDIS/NGSDC, Code D621, 325 Broadway, Boulder CO 80303- (303-497-6338).

Open-File Report↗

USGS1982

High-resolution seismic-reflection profiles collected aboard R/V James M. Gilliss Cruise GS-7903-3, over the Atlantic Continental Slope and Rise off New England

During June 1979, the U.S. Geological Survey (USGS) collected 4,032 km of single-channel seismic-reflection data from the Atlantic Continental Slope and Rise off New England. The work was conducted aboard R/V JAMES M. GILLISS (cruise GS-7903-3). The purpose of the cruise was to determine the characteristics of mass sediment movement on the Continental Slope, and to study and correlate the stratigraphy of the Jurassic and Cretaceous strata lying north and south of the New England seamount chain. Seismic instrumentation included 40-in 3 , 160-in 3 , and 500-in 3 airguns; a Teledyne 800-joule minisparker system; a 3-5-kHz to 7-kHz, hull-mounted tunable transducer; and a 7-channel analog tape recorder. Navigation control during the cruise was provided by a Western Integrated Navigation System capable of integrating satellite, rho-rho Loran-C, hyperbolic Loran-C, gyro compass, and doppler speed-log position data. The prime navigation sensor was the rho-rho Loran-C automatically recorded at 20-second intervals and manually plotted every 15 minutes, backed up by hyperbolic Loran-C fixes automatically recorded every 5 minutes. Of the 4,032 km of data collected, 3,257 km of 3-5-kHz, minisparker and 40-in 3 airgun were for the sediment-slump studand the other 775 km of 3-5-kHz, minis parker, 160-in 3 air gun and 500-in 3 airgun were for the deep stratigraphy study. Overall, the quality of the data is excellent with good resolution and penetration. The original data may be examined at the U.S. Geological Survey, Woods Hole, MA 02543. Copies of the data can be purchased only from the National Geophysical and Solar-Terrestrial Data Center, NOAA/EDIS/NGSDC, Code D621, 325 Broadway, Boulder, CO 80303 (303-497-6338).

Open-File Report↗

USGS1983

Shallow structure and stratigraphy of the carbonate West Florida continental slope and their implications to sedimentation and geohazards

An 1800-joule sparker survey of the West Florida continental slope between about 26?N and 29?15?N showed a top bed of Pleistocene age forming an irregular drape over a surface that is probably Pliocene. The contact between the top two layers is unconformable in the south and, in some places, shows karst collapse and solution features. Karst topography grades into a more hummocky erosional surface to the north, which in turn smoothes out; the contact become conformable still further north. A period of folding, which is widespread over the outer portion of the study area and which may be related to large scale mass wasting, occurred at about the same time represented by the unconformity. Significant subsidence has occurred as late as Pleistocene. The surface layer thins to a minimum (0 in the south) at about 525-meters water depth and then thickens again dramatically to the west, downslope. This thinning is interpreted to be due to the Loop Current, which flows from north to south in the area and which acts to block deposition and scour the bottom. Despite the fact that the margin is dominated by carbonates, usually associated with low sedimentation rates, there is widespread evidence of mass wasting affecting ancient and surficial deposits on the outer part of the upper slope. Three potential groups of geohazards identified are: 1. Potential bottom failure in areas where a thin top layer overlies the karst surface. 2. Potential for sliding and slumping. 3. Scour due to currents which could also affect drilling and engineering activities.

Open-File Report↗

USGS1974

The effect of heated water on the temperature and evaporation of Hyco Lake, North Carolina, 1966-72

Three levels of thermal loading of Hyco Lake by heat from two steam-electric generators have resulted in higher temperatures and increased evaporation in the 3,750-acre (1,518 square hectometer) lake. During the winter, local temperature increases of 34°F (19°C) were sometimes observed at the surface as heated water spread out on top of the cooler, more-dense, lake water, affecting areas as large as 2,590 acres (1,048 square hectometers) with temperature increases averaging up to 12°F (6.7°C) higher than natural lake temperatures. In the summer average temperature increases at the surface seldom exceeded 6°F (3.3°C) and the maximum area affected was 2,570 acres (1,040 square hectometers). Forced evaporation from the heated part of Hyco Lake increased in proportion to the added heat, reaching a maximum of 23.1 inches (586 millimeters) in 1970, as compared to 55.6 inches (1,412 millimeters) of natural evaporation for that year. In 1969, over the heated area, 210,600 British thermal units per square foot per year or 2,407,510,000 joules per square meter per year of heat were added to the lake. Of this amount, about 58 percent of the heat was utilized for evaporation, 24 percent for back radiation, 8.0 percent was conducted as sensible heat from the lake, 1.0 percent was removed through outflow, and 0.04 percent was advected by the evaporated water. These percentages are fairly typical of the first three stages of thermal loading.

North Carolina↗

USGS1976

High-resolution seismic reflection profiling for mapping shallow aquifers in Lee County, Florida

High-resolution continuous seismic reflection profiling equipment was utilized to define the configuration of sedimentary layers underlying part of Lee County, Florida. About 45 miles (72 kilometers) of profile were made on the Caloosahatchee River Estuary and San Carlos Bay. Two different acoustic energy sources, a high resolution boomer and a 45-electrode high resolution sparker, both having a power input of 300 joules, were used to obtain both adequate penetration and good resolution. The seismic profiles show that much of the strata of middle Miocene to Holocene age apparently are extensively folded but not faulted. Initial interpretations indicate that: (1) the top of the Hawthorn Formation (which contains the upper Hawthorn aquifer) has much relief due chiefly to apparent folding; (2) the limestone, sandstone, and unconsolidated sand and phosphorite, which together compose the sandstone aquifer, appear to be discontinuous; (3) the green clay unit of the Tamiami Formation contains large scale angular beds dipping eastward; and (4) numerous deeply cut alluvium-filled paleochannels underlie the Caloosahatchee River. (Woodard-USGS)

Florida↗

USGS1984

Seismicity and eruptive activity at Fuego Volcano, Guatemala: February 1975 -January 1977

We examine seismic and eruptive activity at Fuego Volcano (14??29???N, 90?? 53???W), a 3800-m-high stratovolcano located in the active volcanic arc of Guatemala. Eruptions at Fuego are typically short-lived vulcanian eruptions producing ash falls and ash flows of high-alumina basalt. From February 1975 to December 1976, five weak ash eruptions occurred, accompanied by small earthquake swarms. Between 0 and 140 (average ??? 10) A-type or high-frequency seismic events per day with M > 0.5 were recorded during this period. Estimated thermal energies for each eruption are greater by a factor of 106 than cumulative seismic energies, a larger ratio than that reported for other volcanoes. Over 4000 A-type events were recorded January 3-7, 1977 (cumulative seismic energy ??? 109 joules), yet no eruption occurred. Five 2-hour-long pulses of intense seismicity separated by 6-hour intervals of quiescence accounted for the majority of events. Maximum likelihood estimates of b-values range from 0.7 ?? 0.2 to 2.1 ?? 0.4 with systematically lower values corresponding to the five intense pulses. The low values suggest higher stress conditions. During the 1977 swarm, a tiltmeter located 6 km southeast of Fuego recorded a 14 ?? 3 microradian tilt event (down to SW). This value is too large to represent a simple change in the elastic strain field due to the earthquake swarm. We speculate that the earthquake swarm and tilt are indicative of subsurface magma movement. ?? 1984.

Journal of Volcanology and Geothermal Research↗

USGS1986

The initial giant umbrella cloud of the May 18th, 1980, explosive eruption of Mount St. Helens

The initial eruption column of May 18th, 1980 reached nearly 30 km altitude and released 1017 joules of thermal energy into the atmosphere in only a few minutes. Ascent of the cloud resulted in forced intrusion of a giant umbrella-shaped cloud between altitudes of 10 and 20 km at radial horizontal velocities initially in excess of 50 m/s. The mushroom cloud expanded 15 km upwind, forming a stagnation point where the radial expansion velocity and wind velocity were equal. The cloud was initiated when the pyroclastic blast flow became buoyant. The flow reduced its density as it moved away from the volcano by decompression, by sedimentation, and by mixing with and heating the surrounding air. Observations indicate that much of the flow, covering an area of 600 km2, became buoyant within 1.5 minutes and abruptly ascended to form the giant cloud. Calculations are presented for the amount of air that must have been entrained into the flow to make it buoyant. Assuming an initial temperature of 450??C and a magmatic origin for the explosion, these calculations indicate that the flow became buoyant when its temperature was approximately 150??C and the flow consisted of a mixture of 3.25 ?? 1011 kg of pyroclasts and 5.0 ?? 1011 kg of air. If sedimentation is considered, these figures reduce to 1.1 ?? 1011 kg of pyroclasts and 1.0 ?? 1011 kg of air. ?? 1986.

Journal of Volcanology and Geothermal Research↗

USGS2000

Reevaluation of tsunami formation by debris avalanche at Augustine Volcano, Alaska

Debris avalanches entering the sea at Augustine Volcano, Alaska have been proposed as a mechanism for generating tsunamis. Historical accounts of the 1883 eruption of the volcano describe 6- to 9-meter-high waves that struck the coastline at English Bay (Nanwalek), Alaska about 80 kilometers east of Augustine Island. These accounts are often cited as proof that volcanigenic tsunamis from Augustine Volcano are significant hazards to the coastal zone of lower Cook Inlet. This claim is disputed because deposits of unequivocal tsunami origin are not evident at more than 50 sites along the lower Cook Inlet coastline where they might be preserved. Shallow water (<25 m) around Augustine Island, in the run-out zone for debris avalanches, limits the size of an avalanche-caused wave. If the two most recent debris avalanches, Burr Point (A.D. 1883) and West Island (<500 yr. B.P.) were traveling at velocities in the range of 50 to 100 meters per second, the kinetic energy of the avalanches at the point of impact with the ocean would have been between 1014 and 1015 joules. Although some of this energy would be dissipated through boundary interactions and momentum transfer between the avalanche and the sea, the initial wave should have possessed sufficient kinetic energy to do geomorphic work (erosion, sediment transport, formation of wave-cut features) on the coastline of lowwer Cook Inlet. Because widespread evidence of the effects of large waves cannot be found, it appears that the debris avalanches could not have been traveling very fast when they entered the sea, or they happened during low tide and displaced only small volumes of water. In light of these results, the hazard from volcanigenic tsunamis from Augustine Volcano appears minor, unless a very large debris avalanche occurs at high tide.

Pure and Applied Geophysics↗

USGS2012

Bioenergy potential of the United States constrained by satellite observations of existing productivity

Background/Question/Methods Currently, the United States (U.S.) supplies roughly half the world’s biofuel (secondary bioenergy), with the Energy Independence and Security Act of 2007 (EISA) stipulating an additional three-fold increase in annual production by 2022. Implicit in such energy targets is an associated increase in annual biomass demand (primary bioenergy) from roughly 2.9 to 7.4 exajoules (EJ; 1018 Joules). Yet, many of the factors used to estimate future bioenergy potential are relatively unresolved, bringing into question the practicality of the EISA’s ambitious bioenergy targets. Here, our objective was to constrain estimates of primary bioenergy potential (PBP) for the conterminous U.S. using satellite-derived net primary productivity (NPP) data (measured for every 1 km2 of the 7.2 million km2 of vegetated land in the conterminous U.S) as the most geographically explicit measure of terrestrial growth capacity. Results/Conclusions We show that the annual primary bioenergy potential (PBP) of the conterminous U.S. realistically ranges from approximately 5.9 (± 1.4) to 22.2 (± 4.4) EJ, depending on land use. The low end of this range represents current harvest residuals, an attractive potential energy source since no additional harvest land is required. In contrast, the high end represents an annual harvest over an additional 5.4 million km2 or 75% of vegetated land in the conterminous U.S. While we identify EISA energy targets as achievable, our results indicate that meeting such targets using current technology would require either an 80% displacement of current croplands or the conversion of 60% of total rangelands. Our results differ from previous evaluations in that we use high resolution, satellite-derived NPP as an upper-envelope constraint on bioenergy potential, which removes the need for extrapolation of plot-level observed yields over large spatial areas. Establishing realistically constrained estimates of bioenergy potential seems a critical next step for effectively incorporating bioenergy into future U.S. energy portfolios.

Conference Paper↗

USGS1974

Stabilities of calcite and aragonite

A revaluation of the 25° C activity-product constants of calcite ( K C ) and aragonite ( K A ) was made on the basis of the known solubilities of these phases for which the activity of total dissolved calcium was corrected for the presence of the ion pair CaHCO 3 + in the aqueous phase. The value of the dissociation constant of CaHCO 3 + was taken to be 10 -1.225±0.02 . This value, combined with values of the analytical concentrations in solutions with partial pressure P CO2 =0.97 atmosphere, leads to K C =l0 -8.52±0.04 and K A = 10 -8.36±0.04 . Based on these K values, standard free energies of formation of calcite and aragonite were calculated to be -270,144±375 and -269,926±375 calories mole -1 , (-1,130,282±1,569 and -1,129,370±1,569 joules mole -1 ), respectively. From the 25°C K values, using appropriate entropy and heat capacity data, values of K C and K A were calculated over the temperature range 0° to 200°C. Possible errors in interpretation of measured pH values and inferred P CO2 values and the bearing of these errors on calculations of K values are discussed.

Journal of Research of the U.S. Geological Survey↗