Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “volcanics”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Ambient airborne solids concentrations including volcanic ash at Hanford, Washington sampling sites subsequent to the Mount St. Helens eruption

Airborne solids concentrations were measured on a near daily basis at two Hanford, Washington sites after the eruption of Mount St. Helens on May 18, 1980. These sites are about 211 km east of Mount St. Helens. Collected airborne solids included resuspended volcanic ash plus normal ambient solids. Average airborne solids concentrations were greater at the Hanford meteorological station sampling site which is 24 km northwest of the Horn Rapids dam sampling site. These increased concentrations reflect the sampling site proximity to greater ash fallout depths. Both sites are in low ash fallout areas although the Hanford meteorological station site is closer to the greater ash fallout areas. Airborne solids concentrations were decreased by rain, but airborne solids concentrations rapidly increased as surfaces dried. Airborne concentrations tended to become nearly the same at both sampling sites only for July 12 and 13.

Sehmel, G. A.↗
NASA NTRS1981

Imaging radar observations of volcanic features in Medicine Lake Highland, California

Synthetic aperture L-band radar images of Medicine Lake Highland, California, as obtained from the JPL-NASA aircraft and Seasat orbital systems, are presented. Image interpretation is based on two types of information: slope and topographic effects for geomorphic information, and reflectivity or backscatter in flat terrain which is related to surface roughness and to the surface dielectric constant. Cinder cones and lava tubes are visible (geomorphic features), and three types of lava surfaces are: aa, pahoehoe, and block. In addition, to infer lava flow relative ages, overlapping flow fronts and roughness attenuation observations may be used. It is hoped that this research will improve the understanding of the radar signature of volcanic areas, and will be helpful in interpreting data obtained from spaceborne sensors over the earth and, in particular, Venus.

Farr, T. G.↗
NASA NTRS1982

Mechanisms for lithospheric heat transport on Venus Implications for tectonic style and volcanism

The mechanisms of plate recycling, lithospheric conduction, and hot spot volcanism are each evaluated to determine which is the dominant mode of lithospheric heat transfer on Venus, with attention given to the implications of each mechanism for the interpretation of Venus surface features. It is thought that plate recycling on Venus cannot be excluded on the basis of either theoretical arguments or present observations on topography and radar backscatter. Landforms caused by plate convergence and divergence on Venus, it is noted, would differ substantially from those on the earth owing to the high surface temperature and the absence of oceans on Venus, the lack of free or hydrated water in subducted material, the possibility that subduction would more commonly be accompanied by lithospheric delamination, and the rapid spreading rates that would be required if plate recycling removed a significant fraction of the internal heat. The possibility that the dominant mechanism early in the history of the planet was different from the one at work now is thought to merit consideration.

Solomon, S. C.↗
NASA NTRS1982

Io - A volcanic flow model for the hot spot emission spectrum and a thermostatic mechanism

The hot spots of Io are modeled as a steady state of active areas at 600 K, continuing creation of new lava flows and calderas, cooling off of recent flows and calderas, and the cessation of radiation of old flows and calderas from the accumulation of insulation added by resurfacing. There are three adjustable parameters in this model: the area of active sources at 600 K, the rate of production of new area that is cooling, and the temperature of cessation of emission as the result of resurfacing. The resurfacing rate sets constrains on this last parameter. The emission spectrum computed with reasonable values for these parameters is an excellent match to the spectrum from recent observations. A thermostatic mechanism is described whereby the volcanic activity is turned on for a long period of time and is then turned off for a nearly equal period. As a result the presently observed internal heat flow of approximately 1.5 W/sq m may be as much as twice the rate of production of internal heat. Thus the restrictions placed on theories of tidal dissipation by the observed heat flow may be partially relieved.

Sinton, V. M.↗
NASA NTRS1982

Evolution of the Tharsis province of Mars - The importance of heterogeneous lithospheric thickness and volcanic construction

A new model for the origin and evolution of the Tharsis province that emphasizes that the topography of Tharsis may be produced largely by construction, rather than uplift, is proposed. Underlying the model is the premise that the elastic lithosphere of Mars was laterally heterogeneous early in Martian history; such heterogeneity is discernible later in Martian history from the variable tectonic response of the lithosphere to local surface loads. It is contended that the mechanism for the evolution of Tharsis described here led to permanent topographic and gravity highs and a greatly thickened crust in the Tharsis region. An important advantage of the model is that no anomalous dynamical or chemical properties need be sustained in the Martian mantle beneath Tharsis for billions of years. The mantle beneath Tharsis is thus seen as playing a passive rather than an active role in the regional volcanic and tectonic activity, much like the role of the mantle beneath major midocean ridges on earth.

Solomon, S. C.↗
NASA NTRS1982

Martian volcanic materials - Preliminary thickness estimates in the eastern Tharsis region

Mars displays a variety of volcanic materials from high standing constructs to smooth plains. These materials are evaluated in terms of their susceptibility to thickness determination, and a representative area is analyzed. The Martian ridged plains are much like lunar maria in both surface expression and apparent mode of emplacement. Flooded craters within the ridged plains materials provide an estimate of the thickness distribution. In the Tharsis region, ridged plains materials occur as part of the layered sequence on the east flank of the Tharsis dome. Partially buried craters indicate that the ridged plains materials range from zero meters thick at their eastern limit to over 1.5 km thick westward on the flank of the dome where they are overlain by younger materials. These materials are responsible for only a small portion of the total relief of the Tharsis dome.

De Hon, R. A.↗
NASA NTRS1982

Explosive volcanism on Hecates Tholus, Mars - Investigation of eruption conditions

From a reexamination of the medium and high-resolution Viking images of Amazonian and Hesperian age volcanic centers on Mars, it is believed that an excellent example of well-preserved explosive activity does indeed exist close to the summit of Hecates Tholus. A mantled region to the west of the summit caldera is seen as an example of a geologically very recent plinian air fall ash deposit. Morphological evidence is presented for describing this as explosively generated material, and numerical models of magma ascent and eruption in the Martian environment are used to estimate the physical characteristics (eruption cloud height, magma discharge rate, magma volatile content, duration of activity, and vent size) for this event. Attention is also given to the implication of this eruptive style for the composition of the erupted magma.

Mouginis-Mark, P. J.↗
NASA NTRS1983

Beginning and end of lunar mare volcanism

The distribution and characteristics of the early phases of mare vulcanism on the moon are discussed. Breccias have been observed that indicate the presence of magma flows before 3900 Myr BP. A mafic feature has been identified in more than 100 craters at least 1 km across. The absence of buried mare surfaces on the nearside and western hemispheres is attributed to ejecta deposits, and farside basins with no mare fill are suggested to have experienced early mare flooding. Photographs of the bright-rayed Lichtenberg crater have revealed that mare volcanism occurred within the time frame 1700-2000 Myr BP. It is concluded that the moon featured two periods of igneous activity, the last happening at 1000 Myr BP, and beginning 4300 BP.

Schultz, P. H.↗
NASA NTRS1983

Stratospheric sulfuric acid fraction and mass estimate for the 1982 volcanic eruption of El Chichon

The stratospheric sulfuric acid fraction and mass for the 1982 volcanic eruptions of El Chichon are investigated using data from balloon soundings at Laramie (41 deg N) and in southern Texas (27-29 deg N). The total stratospheric mass of these eruptions is estimated to be approximately 8 Tg about 6.5 months after the eruption with possibly as much as 20 Tg in the stratosphere about 45 days after the eruption. Observations of the aerosol in Texas revealed two primary layers, both highly volatile at 150 C. Aerosol in the upper layer at about 25 km was composed of an approximately 80 percent H2SO4 solution while the lower layer at approximately 18 km was composed of a 60-65 percent H2SO4 solution aerosol. It is calculated that an H2SO4 vapor concentration of at least 3 x 10 to the 7th molecules/cu cm is needed to sustain the large droplets in the upper layer. An early bi-modal nature in the size distribution indicates droplet nucleation from the gas phase during the first 3 months, while the similarity of the large particle profiles 2 months apart shows continued particle growth 6.5 months after the explosion.

Hofmann, D. J.↗
NASA NTRS1982

Climatic influence of background and volcanic stratosphere aerosol models

A simple modelization of the earth atmosphere system including tropospheric and stratospheric aerosols has been derived and tested. Analytical expressions are obtained for the albedo variation due to a thin stratospheric aerosol layer. Also outlined are the physical procedures and the respective influence of the main parameters: aerosol optical thickness, single scattering albedo and asymmetry factor, and sublayer albedo. The method is applied to compute the variation of the zonal and planetary albedos due to a stratospheric layer of background H2SO4 particles and of volcanic ash.

Deschamps, P. Y.↗
NASA NTRS1983

Two classes of volcanic plumes on Io

Results of an analysis of the properties, source regions and deposits of volcanic plumes on Io are presented which suggest the presence of two plume types. Eruptions at the Aten Patera caldera in the south polar region and the Surt caldera in the far north, which were deduced to have taken place between the times of the Voyager 1 and Voyager 2 encounters from evidence of surface changes, are similar to the Pele eruption. These Pele-type eruptions are characterized by durations of from a few days to a few weeks, dark-red annular deposits of about 1400 km in diameter, temperatures of about 650 K and locations restricted to areas with large, silicate landforms. Smaller, more numerous eruptions of the Prometheus type were observed on both encounters, being characterized by durations in excess of several years, bright ringed deposits about 250 km in diameter, restriction to an equatorial location high in SO2 and temperatures less than 400 K. In addition, an intermediate type of feature was noted at either end of the linear feature Loki. Two separate mechanisms, involving SO2 and sulfur as driving sources, are proposed to account for the Pele- and Prometheus-type eruptions, respectively, and the discrete temperatures of the plumes are suggested to reflect the temperatures at which sulfur is a low-viscosity fluid.

Mcewen, A. S.↗
NASA NTRS1982

SIR-A radar images of sand dunes and volcanic fields

Shuttle Imaging Radar (SIR-A) synthetic aperture radar images of sand dunes and volcanic fields are presented and preliminary interpretation provided. The SIR-A images are compared with Seasat images where available. Unvegetated sand dunes are recorded as black areas on SIR-A images due to the specular reflection away from the sensor at the SIR-A incidence angle. Even a very small amount of vegetation provides some backscatter, however. Interdune areas frequently contain rough lag gravels which outline the dunes. Lava flows are typically very rough surfaces which are bright areas on radar images. Cinder cones are smooth and therefore black on the image unless they have a blocky crater rim at the SIR-A incidence angle. Ash dunes and ash fields are smooth and imaged as dark areas.

Blom, R.↗
NASA NTRS1983

Clastic sedimentary rocks of the Michipicoten Volcanic-sedimentary belt, Wawa, Ontario

The Wawa area, part of the Michipicoten greenstone belt, contains rock assemblages representative of volcanic sedimentary accumulations elsewhere on the shield. Three mafic to felsic metavolcanic sequences and cogenetic granitic rocks range in age from 2749 + or - 2Ma to 2696 + or - 2Ma. Metasedimentary rocks occur between the metavolcanic sequences. The total thickness of the supracrustal rocks may be 10,000 m. Most rocks have been metamorphosed under greenschist conditions. The belt has been studied earlier and is currently being remapped by Sage. The sedimentrologic work has been briefly summarized; two mainfacies associations of clastic sedimentary rocks are present - a Resedimented (Turbidite) Facies Association and a Nonmarine (Alluvial Fan Fluvial) Facies Association.

Ojakangas, R. W.↗
NASA NTRS1984

Volcanism and rift formation in Beta Regio, Venus: New radar results

A high-resolution (approximately 2 km) image of Beta Regio, Venus, obtained with the Arecibo radar system, reveals additional details of its structure which seem to confirm past suggestions that this region consists of a rift system and associated volcanism. Numerous long linear features approximately parallel to the north-south trending trough discovered by the Pioneer-Venus Orbiter are interpreted as being indicative of extensive faulting and the detail for the radar reflectivity anomaly coincident with Theia Mons suggests that it is a major volcano situated on what would be the western bounding fault of the rift system.

Campbell, D. B.↗
NASA NTRS1983

Size-specific composition of aerosols in the El Chichon volcanic cloud

A NASA U-2 research aircraft flew sampling missions in April, May, July, November, and December 1982 aimed at obtaining in situ data in the stratospheric cloud produced from the March-April 1982 El Chichon eruptions. Post flight analyses provided information on the aerosol composition and morphology. The particles ranged in size from smaller than 0.05 m to larger than 20 m diameter and were quite complex in composition. In the April, May, and July samples the aerosol mass was dominated by magmatic and lithic particles larger than about 3 m. The submicron particles consisted largely of sulfuric acid. Halite particles, believed to be related to a salt dome beneath El Chichon, were collected in the stratosphere in April and May. On the July 23 flight, copper-zinc oxide particles were collected. In July, November, and December, in addition to the volcanic ash and acid particles, carbon-rich particles smaller than about 0.1 m aerodynamic diameter were abundant.

Woods, D. C.↗
NASA NTRS1983

Relationships between mineralization and silicic volcanism in the central Andes

Existing models for the genesis of porphyry copper deposits indicate that they formed in granodioritic stocks located in the infrastructure of andesitic stratovolcanoes. It is noted that sites of porphyry-type subvolcanic tin mineralization in the Eastern Cordillera of Bolivia are distinguished by the absence of such andesitic structures. The surface expression of a typical subvolcanic porphyry tin deposit is thought to be an extrusive dome of quartz latite porphyry, sometimes related to a larger caldera structure. Evidence from the El Salvador porphyry copper deposit in the Eocene magmatic belt in Chile indicates that it too may be more closely related to a silicic volcanic structure than to an andesitic stratovolcano. The dome of La Soufriere, Guadeloupe is offered as a modern analog for the surface expression of subvolcanic mineralization processes, with the phreatic eruptions there indicating the formation of hydrothermal breccia bodies in depths. It is pointed out that the occurrence of mineralized porphyries, millions of years after caldera formation, does not necessarily indicate that tin intrusions and mineralization are not genetically related to the subcaldera pluton, but may be a consequence of the long thermal histories (1-10 million years) of the lowermost parts of large plutons.

Francis, P. W.↗
NASA NTRS1983

The magma budget of Volcan Arenal, Costa Rica from 1968 to 1980

The magma volume emitted by Volcan Arenal, Costa Rica, has been calculated to be 304 x 10 to the 6th cu m. A near-continuous rise from very deep within the crust is proposed as an explanation for Arenal's magma supply, and the long-term seismic pattern is interpreted as individual batches of magma using previously fractured pathways. During a break in activity (1973) the effusion site moved from Crater A to Crater C, approximately 400 m higher. It is maintained that the steady downward tilting of the volcano's summit was caused by the loading of the volcano's western side by about 19 x 10 to the 6th cu m of lava. Also noted is the abrupt decrease in effusion rate compatible with the increased magmatic head needed to reach Crater C. It is concluded that the constancy of magma composition and effusion rate from 1974 to 1980 indicates a homogeneous magma reservoir.

Wadge, G.↗