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At least 271 records · Page 15

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NASA NTRS1972

Mariner 9 photographs of small-scale volcanic structures on Mars

Surface features on the flanks of Martian shield volcanoes photographed by Mariner 9 are identified as lava flow channels, rift zones, and partly collapsed lava tubes by comparisons with similar structures on the flanks of Mauna Loa shield volcano, Hawaii. From these identifications, the composition of the Martian lava flows is interpreted to be basaltic, with viscosities ranging from those of fluid pahoehoe to more viscous aa.

Greeley, R.↗

NASA NTRS1973

Mariner 9 photographs of small volcanic structures on Mars

Surface features on the flanks of martian shield volcanoes photographed by Mariner 9 are identified as lava flow channels, rift zones, and partly collapsed lava tubes by comparisons with similar structures on the flanks of Mauna Loa shield volcano, Hawaii. From these identification, the composition of the martian lava flows in interpreted to be basaltic, with viscosities ranging from those of fluid pahoehoe to more viscous aa.

Greeley, R.↗

NASA NTRS1991

Magma generation on Mars: Estimated volumes through time

Images of volcanoes and lava flows, chemical analysis by the Viking landers, and studies of meteorites show that volcanism has played an important role in the evolution of Mars. Photogeologic mapping suggests that half of Mars' surface is covered with volcanic materials. Here, researchers present results from new mappings, including estimates of volcanic deposit thicknesses based on partly buried and buried impact craters using the technique of DeHon. The researchers infer the volumes of possible associated plutonic rocks and derive the volumes of magmas on Mars generated in its post-crustal formation history. Also considered is the amount of juvenile water that might have exsolved from the magma through time.

Greeley, Ronald↗

NASA NTRS1992

Textural constraints on effusive silicic volcanism - Beyond the permeable foam model

The paper reports textural observations and presents isotopic evidence from active and recent silicic lava flows which show that at least some vesiculation occurs during surface advance of extrusions, after magma has reached the earth's surface. This view is in contrast to the widely promoted 'permeable foam' model, which states that all volatiles escape during ascent of the magma, and that all dense glassy material in lava flows forms from the collapse of pumiceous lava, i.e., that silicic lavas emerge as highly inflated foam flows. The permeable foam model also implies the unlikely requirement that explosive-to-effusive transitions be associated with an increase in the eruption rate. A more comprehensive model for the emplacement of silicic extrusions that allows for early gas loss during ascent, as well as late-stage vesiculation, is presented. The way in which the redistribution of volatiles during surface flow can increase explosive hazards from silicic lavas days, weeks, or months after the lava emerges from the event is discussed.

Fink, Jonathan H.↗

NASA NTRS1992

Zagami - Product of a two-stage magmatic history

Results of petrologic studies of new large samples of the Zagami shergottite are presented. Pyroxene crystals have homogeneous Mg-rich pigeonite and augite cores, overgrown by Fe-rich zoned pyroxene rims. Amphibole-bearing magmatic inclusions occur exclusively in the cores. It is concluded that Zagami experienced a two-stage crystallization history. The first stage occurred in a deep-seated, slowly cooling magma chamber. There, the homogeneous Mg-rich cores of the pyroxenes crystallized during relatively slow cooling. During the second stage, the Mg-rich pyroxenes were entrained into a magma that either intruded to the near-surface and cooled in a relatively thin dike or sill, or extruded to the surface and crystallized in a lava flow greater than 10 m thick, again without indications of crystal settling. The estimated depth of the magma chamber for Zagami of greater than 7.5 km and thickness of the putative lava flow of greater than 10 m are consistent with calculations and observations of volcanic constructs and flows in the Tharsis region of Mars.

Mccoy, Timothy J.↗

NASA NTRS2009

Volcanism on Io: Insights from Global Geologic Mapping

We are preparing a new global geo-logic map of Jupiter s volcanic moon, Io. Here we report the type of data that are now available from our global mapping efforts, and how these data can be used to investigate questions regarding the volcano-tectonic evolution of Io. We are using the new map to investigate several specific questions about the geologic evolution of Io that previously could not be well addressed, including (for example) a comparison of the areas vs. the heights of Ionian mountains to assess their stability and evolution (Fig. 1). The area-height relationships of Io s visible mountains show the low abundance and low relief of volcanic mountains (tholi) relative to tectonic mountains, consistent with formation from low-viscosity lavas less likely to build steep edifices. Mottled mountains are generally less high than lineated mountains, consistent with a degradational formation.

Williams, D. A.↗

NASA NTRS1979

Volcano-ice interactions on Mars

Central volcanic eruptions beneath terrestrial glaciers have built steep-sided, flat-topped mountains composed of pillow lava, glassy tuff, capping flows, and cones of basalt. Subglacial fissure eruptions produced ridges of similar composition. In some places the products from a number of subglacial vents have combined to form widespread deposits. The morphologies of these subglacial volcanoes are distinctive enough to allow their recognition at the resolutions characteristic of Viking orbiter imagery. Analogs to terrestrial subglacial volcanoes have been identified on the northern plains and near the south polar cap of Mars. The polar feature provides probable evidence of volcanic eruptions beneath polar ice. A mixed unit of rock and ice is postulated to have overlain portions of the northern plains, with eruptions into this ground ice having produced mountains and ridges analogous to those in Iceland. Subsequent breakdown of this unit due to ice melting revealed the volcanic features. Estimated heights of these landforms indicate that the ice-rich unit once ranged from approximately 100 to 1200 m thick.

Allen, C. C.↗

NASA NTRS2001

Estimating Expressed Temperature and Fractional Area of Hot Lava at the Kilauea Vent with AVIRIS Spectral Measurements

Imaging spectroscopy offers a framework based in physics and chemistry for scientific investigation of a wide range of phenomena of interest in the Earth environment. In the scientific discipline of volcanology knowledge of lava temperature and distribution at the surface provides insight into the volcano status and subsurface processes. A remote sensing strategy to measure surface lava temperatures and distribution would support volcanology research. Hot targets such as molten lava emit spectral radiance as a function of temperature. A figure shows a series of Planck functions calculated radiance spectra for hot targets at different temperatures. A maximum Lambertian solar reflected radiance spectrum is shown as well. While similar in form, each hot target spectrum has a unique spectral shape and is distinct from the solar reflected radiance spectrum. Based on this temperature-dependent signature, imaging spectroscopy provides an innovative approach for the remote-sensing-based measurement of lava temperature. A natural site for investigation of the measurement of lava temperature is the Big Island of Hawaii where molten lava from the Kilauea vent is present at the surface. In the past, Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data sets have been used for the analysis of hot volcanic targets and hot burning fires. The research presented here builds upon and extends this earlier work. The year 2000 Hawaii AVIRIS data set has been analyzed to derive lava temperatures taking into account factors of fractional fill, solar reflected radiance, and atmospheric attenuation of the surface emitted radiance. The measurements, analyses, and current results for this research are presented here.

Green, Robert O.↗

NASA NTRS1980

Volcanic features of Hawaii. A basis for comparison with Mars

Despite the difference in size Martian and Hawaiian volcanoes have numerous characteristics in common. Specific features such as lava channels, collapsed lava tubes, levees and flow fronts, all very common in Hawaii, are also abundant on the flanks of some of the Martian volcanoes. Striking differences also exist, such as the apparent lack of radial rift zones on some Martian volcanoes and the paucity of cinder and spatter cones. Some of the best photographs of Martian and Hawaiian volcanic features are presented. Descriptive legends are provided for each picture. An overview of the geological processes and structures depicted is included.

Carr, M. H.↗

NASA NTRS1992

Mylitta Fluctus, Venus - Rift-related, centralized volcanism and the emplacement of large-volume flow units

The flow morphology, stratigraphy, and evoluton of Mylitta Fluctus, a massive lava flow field on Venus, is characterized, and the link between its origin and the local tectonics is examined. The regional setting of the flow field is reviewed. A model for the stratigraphy and emplacement history of Mylitta is developed, flow morphology is discussed, and some preliminary estimates of effusion rates and eruption durations that may have characterized its emplacement are presented. The origin of Mylitta is discussed in relation to local rifting and possible hotspot activity, and the emplacement of Mylitta is compared to the origin of terrestrial flood basalts.

Roberts, Kari M.↗

NASA NTRSDate not supplied

The Project “Analogs for VENus’s GEologically Recent Surfaces” (AVENGERS): Unveiling Active Volcanism on Venus

The recently selected missions to Venus opened a new era for the exploration of the Earth’s hellish twin sister. One of the key questions that the selected missions to Venus will address is whether the planet is volcanically active. The identification of ongoing volcanic activity on Venus can indeed unveil important clues on the geologic evolution of the planet, also helping us to better understand how volcanic and atmospheric processes work on Earth, especially those related to the climate change produced by greenhouse gases. To fully contextualize the higher resolution datasets to be provided by the future missions to Venus, we need to be able to exploit the wealth of data to be produced in the best possible way. Different types of instruments will indeed perform unprecedent orbiting and in-situ investigations of the surface and subsurface of Venus. To this regard, the Project “Analogs for VENus’s GEologically Recent Surfaces” (AVENGERS) aims to build a comprehensive database of Terrestrial active volcanoes which may act as suitable analogs for identifying ongoing volcanic activity on Venus. To do this, the project AVENGERS will combine the implementation of terrestrial orbiter radar data analysis techniques (i.e., radar interferometry) with infrared and laboratory analyses of lava flow samples from Terrestrial active volcanoes. As a first suitable analog of the Project AVENGERS, we selected Mount Etna in Sicily for a direct comparison with potentially active volcanic structures of Venus, and with Idunn Mons, one of the most promising possibly active volcanoes of Venus. Given its composite nature, Mount Etna offers the opportunity to identify and study multiple types of eruptive products (both effusive and explosive) from the analysis of high-resolution radar images. The frequent eruptions characterizing this volcano will also allow to test techniques of radar interferometry. Moreover, its ease of access facilitates geologic field trips and in-situ investigations with related sample retrieving. Ongoing infrared laboratory analysis on several altered and unaltered samples retrieved by Mount Etna will help to distinguish spectral signatures of fresh vs weathered volcanic deposits.

P. D’Incecco↗

NASA NTRS2008

Global Geologic Mapping of Io: Preliminary Results

A new global geologic map of Jupiter's volcanic moon, Io is being prepared, with the focus being on completion of a draft map by July 2008. Here initial results of the mapping are reported: a preliminary distribution of material units in terms of areas and a visual representation. Additionally, the mapping hopes to address some of the problems in Io geology. Thus far it has been discovered that Io's surface is dominated by plains material, thought to consist of Io's silicate crust covered by pyroclastic deposits and lava flows of silicate and sulfur-bearing composition. Many plains areas contain flow fields that cannot be mapped separately due to a lack of resolution or modification by alteration processes. Discrete lava flows and flow fields are the next most abundant unit, with bright (sulfur?) flows in greater abundance than dark (silicate?) flows. The source of most of Io's heat flow, the paterae, are the least abundant unit in terms of areal extent.Upon completion of the draft map for peer review, it will be used to investigate several specific questions about the geological evolution of Io that previously could not be well addressed, including: comparison of the areas versus the heights of Ionian mountains to assess their stability and evolution; correlation and comparison of Galileo Near-Infrared Mapping Spectrometer and Photopolarimeter-Radiometer hot spot locations with the mapped location of dark versus bright lava flows and patera floors to assess any variations in the types of sources for Io's active volcanism; and the creation of a global inventory of the areal coverage of dark and bright laval flows to assess the relative importance of sulfur versus silicate volcanism in resurfacing Io, and to assess whether there are regional concentrations of either style of volcanism that may have implications on interior processes.

Williams, David A.↗

NASA NTRS1973

Some volcanic and structural features of Mare Serenitatis

Relationships between volcanic and structural features along the southern edge of Mare Serenitatis as determined from low angle lighting in Apollo 17 photographs are discussed. Observational summaries are given of: (1) contact relations between the dark border material and the central mare fill, (2) a late stage lava flow with associated cinder cones, and (3) certain structural features related to the development of the mare basin and its associated volcanic landforms. A chronologic summary is given of volcanic and structural events believed to be critical to understanding the development of Mare Serenitatis.

Bryan, W. B.↗

NASA NTRS1979

Volcanic features of Io

The various volcanic landforms observed on Io by Voyager 1 are described and compared with similar features on earth. Ionian calderas, observed to cover 5% of the surface, are generally found to be of low relief, similar to certain terrestrial calderas. Flow patterns observed include dark, linear markings with lobate margins resembling terrestrial lava flows, bright lobate markings originating at calderas, and a bright flow feature surrounding the calderas. Positive relief features associated with volcanic structures include pancake-like constructions similar to low volcanic cones, sheet-like structures, rugged mountains, and a type of surface upheaval. Bright and dark diffuse markings have also been found. The implications of the high rates of volcanic activity and the apparent abundance of sulfur on Io for the type of volcanism observed are discussed, and it is concluded that while there are strong arguments for sulfur flows on the surface of Io, silicate volcanism of the type observed on earth may also occur.

Carr, M. H.↗

NASA NTRS1973

Geological and geophysical remote sensing of Iceland

The author has identified the following significant results. A binational, multidisciplinary research effort in Iceland is directed at an analysis of MSS imagery from ERTS-1 to study a variety of geologic, hydrologic, oceanographic, and agricultural phenomena. Initial findings are: (1) recent lava flows can be delineated from older ones; (2) ERTS-1 and NOAA-2 recorded volcanic eruptions on Heimaey, Vestmann Islands; (3) coastline changes are mappable; (4) areas covered with new or residual snow can be mapped, and dark appearance of newly fallen snow on band 7 appears to be related to melting; (5) sediment plumes from discharge of glacial rivers can be delineated; (6) the area encompassed by glacial ice can be mapped, including the new position of a surging glacier, Eyjabakkajokull, and related phenomena of nunataks and moraines; (7) changes in position of rivers, lake sizes, and new lakes can be mapped; (8) low sun angle imagery enhances the morphologic expression of constructional glacial and volcanic landforms; (9) MSS color composites permit regional mapping of distribution of vegetation; and (10) at least at 1:250, 000 map scale and smaller, ERTS-1 imagery provides a means of updating various types of maps of Iceland and will permit the compilation of maps specifically aimed at those dynamic environmental phenomena which impact on the Icelandic economy.

Williams, R. S., Jr.↗

NASA NTRS1992

Global scale concentrations of volcanic activity on Venus: A summary of three 23rd Lunar and Planetary Science Conference abstracts. 1: Venus volcanism: Global distribution and classification from Magellan data. 2: A major global-scale concentration of volcanic activity in the Beta-Atla-Themis region of Venus. 3: Two global concentrations of volcanism on Venus: Geologic associations and implications for global pattern of upwelling and downwelling

As part of the analysis of data from the Magellan Mission, we have compiled a global survey of the location, dimensions, and subsidiary notes of all identified volcanic features on Venus. More than 90 percent of the surface area was examined and the final catalog comprehensively identifies 1548 individual volcanic features larger than approximately 20 km in diameter. Volcanic features included are large volcanoes, intermediate volcanoes, fields of small shield volcanoes, calderas, large lava channels, and lava floods as well as unusual features first noted on Venus such as coronae, arachnoids, and novae.

Crumpler, L. S.↗

NASA NTRS1995

The Spreading of Variable-Viscosity Axisymmetric Radial Gravity Currents: Applications to the Emplacement of Venusian 'Pancake' Domes

The Magellan images of Venus have revealed a number of intriguing volcanic features, including the steep-sided or 'pancake' domes. These volcanic domes or flows have morphologies that suggest formation by a single continuous emplacement of lava with a higher viscosity than that of the surrounding basaltic plains. Numerous investigators have suggested that such high viscosity is due to high silica content, leading to the conclusion that the domes are evidence of evolved magmatic products on Venus. However, viscosity depends on crystallinity as well as on silica content: high viscosity could therefore also be due to a cooler (and therefore higher crystal content) lava. Models of dome emplacement which include both cooling and composition factors are thus necessary in order to determine the ranges of crystallinity and silica content which might lead to the observed gross dome morphologies. Accordingly, in this study domes are modelled as radial viscous gravity currents with an assumed cooling-induced viscosity increase to include both effects. Analytical and numerical results indicate that pancake dome formation is feasible with compositions ranging from basaltic to rhyolitic. Therefore, observations of gross dome morphology alone are insufficient for determining composition and the domes do not necessarily represent strong evidence for evolved magmatism on Venus.

Sakimoto, S. E. H.↗

NASA NTRS1997

Temperature and Area Constraints of the South Volund Volcano on IO from the NIMS and SSI instruments during the Galileo G1 Orbit

Analysis of data from darkside and eclipse observations of Io by the NIMS and SSI instruments show that the South Volund hot spot is a manifestation of high temperature active silicate volcanism. The NIMS data are fitted with a two temperature model (developed from modelling terrestrial lavas) which yields a better fit to the data than a single temperature fit.

Eclipes↗