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30 records · Page 2Linked to original sources

Volatiles in basaltic glasses from a subglacial volcano in northern British Columbia (Canada): Implications for ice sheet thickness and mantle volatiles

Dissolved H 2 O, CO 2 , S and Cl concentrations were measured in glasses from Tanzilla Mountain, a 500 m-high, exposed subglacial volcano from the Tuya-Teslin region, north central British Columbia, Canada. The absence of a flat-topped subaerial lava cap and the dominance of pillows and pillow breccias imply that the Tanzilla Mountain volcanic edifice did not reach a subaerial eruptive phase. Lavas are dominantly tholeiitic basalt with minor amounts of alkalic basalt erupted at the summit and near the base. Tholeiites have roughly constant H 2 O (c.0.56 ± 0.07 wt%), CO 2 (<30 ppm), S ( 980+ or -30 ppm) and Cl ( 200+ or -20 ppm) concentrations. Alkalic basalts have higher and more variable volatile concentrations that decrease with increasing elevation (0.62-0.92 wt% H2O, <30 ppm CO 2 , 870-1110 ppm S and 280-410 ppm Cl) consistent with eruptive degassing. Calculated vapour saturation pressures for the alkalic basalts are 36 to 81 bars corresponding to ice thicknesses of 400 to 900 m. Maximum calculated ice thickness (c. 1 km) is at the lower end of the range of predicted maximum Fraser glaciation (c. 1-2 km), and may indicate initiation of volcanism during the waning stages of glaciation. Temporal evolution from tholeiitic to alkalic compositions may reflect compositional gradients within a melting column, instead of convective processes within a stratified magma chamber. The mantle source region for the subglacial volcanoes is enriched in incompatible elements similar to that for enriched mid-oceanic ridge basalt (e.g. Endeavour Ridge) and does not contain residual amphibole. Thus, metasomatic enrichment most likely reflects small degree partial melts rather than hydrous fluids.

Geological Society Special Publication↗

Esperance: Multiple episodes of aqueous alteration involving fracture fills and coatings at Matijevic Hill, Mars

In the search for evidence of past aqueous activity by the Mars Exploration Rover Opportunity, fracture-filling veins and rock coatings are prime candidates for exploration. At one location within a segment of remaining rim material surrounding Endeavour Crater, a set of &ldquo;boxwork&rdquo; fractures in an outcrop called Esperance are filled by a bright, hydrated, and highly siliceous (SiO 2 ~ 66 wt%) material, which has overall a montmorillonite-like chemical composition. This material is partially covered by patches of a thin, dark coating that is sulfate-rich (SO 3 ~ 21 wt%) but also contains significant levels of Si, Fe, Ca, and Mg. The simultaneous presence of abundant S, Si, and Fe indicates significant mineralogical complexity within the coating. This combination of vein and coating compositions is unlike previous analyses on Mars. Both materials are heterogeneously eroded, presumably by eolian abrasion. The evidence indicates at least two separate episodes of solute precipitation from aqueous fluids at this location, possibly widely separated in time. In addition to the implications for multiple episodes of alteration at the surface of the planet, aqueous chemical environments such as these would have been habitable at the time of their formation and are also favorable for preservation of organic material.

American Mineralogist↗

Shuttle Radar Topography Mission (SRTM)

Under an agreement with the National Aeronautics and Space Administration (NASA) and the Department of Defense's National Imagery and Mapping Agency (NIMA), the U.S. Geological Survey (USGS) is now distributing elevation data from the Shuttle Radar Topography Mission (SRTM). The SRTM is a joint project between NASA and NIMA to map the Earth's land surface in three dimensions at a level of detail unprecedented for such a large area. Flown aboard the NASA Space Shuttle Endeavour February 11-22, 2000, the SRTM successfully collected data over 80 percent of the Earth's land surface, for most of the area between 60? N. and 56? S. latitude. The SRTM hardware included the Spaceborne Imaging Radar-C (SIR-C) and X-band Synthetic Aperture Radar (X-SAR) systems that had flown twice previously on other space shuttle missions. The SRTM data were collected specifically with a technique known as interferometry that allows image data from dual radar antennas to be processed for the extraction of ground heights.

Fact Sheet↗

Shuttle Radar Topography Mission (SRTM)

Under an agreement with the National Aeronautics and Space Administration (NASA) and the Department of Defense's National Geospatial-Intelligence Agency (NGA), the U.S. Geological Survey (USGS) is distributing elevation data from the Shuttle Radar Topography Mission (SRTM). The SRTM is a joint project of NASA and NGA to map the Earth's land surface in three dimensions at an unprecedented level of detail. As part of space shuttle Endeavour's flight during February 11-22, 2000, the SRTM successfully collected data over 80 percent of the Earth's land surface for most of the area between latitudes 60 degrees north and 56 degrees south. The SRTM hardware included the Spaceborne Imaging Radar-C (SIR-C) and X-band Synthetic Aperture Radar (X-SAR) systems that had flown twice previously on other space shuttle missions. The SRTM data were collected with a technique known as interferometry that allows image data from dual radar antennas to be processed for the extraction of ground heights.

Fact Sheet↗

Digital shaded-relief map of Venezuela

The digital shaded relief map of Venezuela is a composite of 3-arc-second (approximately 90-meter) elevation data, captured during the Shuttle Radar Topography Mission (SRTM) in February 2000. The SRTM, a joint project between the National Geospatial-Intelligence Agency (NGA) and the National Aeronautics and Space Administration (NASA), provides the most comprehensive international digital elevation dataset ever produced. The 11-day flight mission aboard the U.S. Space Shuttle Endeavour obtained elevation data for about 80% of the world's landmass through the use of single-pass Interferometric Synthetic Aperture Radar (InSAR) technology. This publication includes a colorized relief image of Venezuela (GeoTIFF format) and the elevation data (ESRI Grid format) used for rendering the image. These datasets are intended to accompany U.S. Geological Survey Open-File Report 2005–1038 ( http://pubs.usgs.gov/of/2005/1038/ ) and U.S. Geological Survey Data Series 199 ( http://pubs.usgs.gov/ds/2006/199/ ). SRTM data in version 2.0 have been processed using the latest data-void filling algorithms and represent a significant improvement to the data used in version 1.0.

Open-File Report↗

GEOS seismograms recorded for aftershocks of the earthquakes of December 7, 1988, near Spitak, Armenia SSR, during the time period 26 December 1988 14:00 through 29 December 1988 (UTC)

The earthquakes of December 7, 1988, near Spitak, Armenia SSR, serve as another grim reminder of the serious hazard that earthquakes pose throughout the world. We extend our heartfelt sympathies to the families of the earthquake victims and intend that our cooperative scientific endeavours will help reduce losses in future earthquakes. Only through a better understanding of earthquake hazards can earthquake losses be reduced for all peoples in seismically active regions of the world. The tragic consequences of these earthquakes remind scientists and public officials alike of their urgent responsibilities to understand and mitigate the effects of earthquakes. On behalf of the U.S. Geological Survey, I would like to express appreciation to our Soviet colleagues for their kind invitation to participate in joint scientific and engineering studies. Without their cooperation and generous assistance, the conduct of these studies would not have been possible. This report provides seismologic and geologic data collected during the time period December 21, 1988, through February 2, 1989. These data are presented in their entirety to expedite analysis of the data set for inferences regarding hazard mitigation actions, applicable not only in Armenia but other regions of the world exposed to high seismic risk.

Open-File Report↗

GEOS seismograms for aftershocks of the earthquakes of December 7, 1988, near Spitak, Armenia SSR, during the time period 30 December 1988 14:00 through 2 January 1989 (UTC): Chapter D in Results and data from seismologic and geologic studies following earthquakes of December 7, 1988, near Spitak, Armenia SSR (Open-File Report 89-163)

The earthquakes of December 7, 1988, near Spitak, Armenia SSR, serve as another grim reminder of the serious hazard that earthquakes pose throughout the world. We extend our heartfelt sympathies to the families of the earthquake victims and intend that our cooperative scientific endeavours will help reduce losses in future earthquakes. Only through a better understanding of earthquake hazards can earthquake losses be reduced for all peoples in seismically active regions of the world. The tragic consequences of these earthquakes remind scientists and public officials alike of their urgent responsibilities to understand and mitigate the effects of earthquakes. On behalf of the U.S. Geological Survey, I would like to express appreciation to our Soviet colleagues for their kind invitation to participate in joint scientific and engineering studies. Without their cooperation and generous assistance, the conduct of these studies would not have been possible. This report provides seismologic and geologic data collected during the time period December 21, 1988, through February 2, 1989. These data are presented in their entirety to expedite analysis of the data set for inferences regarding hazard mitigation actions, applicable not only in Armenia but other regions of the world exposed to high seismic risk

Spitak↗

GEOS seismograms recorded for aftershocks of the earthquakes of December 7, 1988, near Spitak, Armenia SSR, during the time period 3 January 1989 through 2 February 1988 (UTC)

The earthquakes of December 7, 1988, near Spitak, Armenia SSR, serve as another grim reminder of the serious hazard that earthquakes pose throughout the world. We extend our heartfelt sympathies to the families of the earthquake victims and intend that our cooperative scientific endeavours will help reduce losses in future earthquakes. Only through a better understanding of earthquake hazards can earthquake losses be reduced for all peoples in seismically active regions of the world. The tragic consequences of these earthquakes remind scientists and public officials alike of their urgent responsibilities to understand and mitigate the effects of earthquakes. On behalf of the U.S. Geological Survey, I would like to express appreciation to our Soviet colleagues for their kind invitation to participate in joint scientific and engineering studies. Without their cooperation and generous assistance, the conduct of these studies would not have been possible. This report provides seismologic and geologic data collected during the time period December 21, 1988, through February 2, 1989. These data are presented in their entirety to expedite analysis of the data set for inferences regarding hazard mitigation actions, applicable not only in Armenia but other regions of the world exposed to high seismic risk

Open-File Report↗

Increasing the availability of national mapping products.

A discussion of the means employed by the US Geological Survey to facilitate map usage, covering aspects of project Map Accessibility Program including special rolled and folded map packaging, new market testing, parks and campgrounds program, expanded map dealer program, new booklet-type State sales index and catalog and new USGS map reference code. The USGS is seen as the producer of a tremendous nation-wide inventory of topographic and related map products available in unprecedented types, formats and scales, and as endeavouring to increase access to its products. The new USGS map reference code is appended. -J.C.Stone

Information Bulletin, Western Association of Map L↗

Managing harvest and habitat as integrated components

In 2007, several important initiatives in the North American waterfowl management community called for an integrated approach to habitat and harvest management. The essence of the call for integration is that harvest and habitat management affect the same resources, yet exist as separate endeavours with very different regulatory contexts. A common modelling framework could help these management streams to better understand their mutual effects. Particularly, how does successful habitat management increase harvest potential? Also, how do regional habitat programmes and large-scale harvest strategies affect continental population sizes (a metric used to express habitat goals)? In the ensuing five years, several projects took on different aspects of these challenges. While all of these projects are still on-going, and are not yet sufficiently developed to produce guidance for management decisions, they have been influential in expanding the dialogue and producing some important emerging lessons. The first lesson has been that one of the more difficult aspects of integration is not the integration across decision contexts, but the integration across spatial and temporal scales. Habitat management occurs at local and regional scales. Harvest management decisions are made at a continental scale. How do these actions, taken at different scales, combine to influence waterfowl population dynamics at all scales? The second lesson has been that consideration of the interface of habitat and harvest management can generate important insights into the objectives underlying the decision context. Often the objectives are very complex and trade-off against one another. The third lesson follows from the second &ndash; if an understanding of the fundamental objectives is paramount, there is no escaping the need for a better understanding of human dimensions, specifically the desires of hunters and nonhunters and the role they play in conservation. In the end, the compelling question is how to better understand, guide and justify decisions about conservation investments in waterfowl management. Future efforts to integrate harvest and habitat management will include completion of the species-specific case-studies, initiation of policy discussions around how to integrate the decision contexts and governing institutions, and possible consideration of a new level of integration &ndash; integration of harvest and habitats management decisions across waterfowl stocks.

Wildfowl↗

A journey to the center of the USGS National Strong-motion Project processing and beyond

The United States Geological Survey (USGS) National Strong Motion Project (NSMP) has the primary U.S. government responsibility to acquire, process, and disseminate significant strong-motion earthquake ground motion records measured at surficial free-field stations, structures (buildings, dams, and bridges, and geotechnical arrays to the earthquake engineering community. As a result of the deployment of modern seismic instrumentation and growth of tools such as web-services, earthquake data from U.S. and international seismic networks are more accessible than ever. Our mission is to provide raw and processed strong-motion waveforms with PGA values greater than 0.1%g for M3.0 earthquakes and larger in California and M4.0 and larger within the conterminous US, Hawaii, Puerto Rico, and Alaska. Datasets of interest to the engineering and geophysics communities, such as event sequences in areas of induced seismicity and significant global events, are also processed and posted at the Center for Engineering Strong Motion Data (CESMD) at strongmotioncenter.org when available through collaboration with the international strong-motion data community. Here we outline (1) the NSMP’s current workflow to acquire, process, and distribute data at CESMD; (2) our new endeavours and collaborations focusing on comparison and integration of waveform processing software, development of techniques for metadata quality checks before and after earthquakes, and construction of a dynamic site characterization repository; and (3) our topics for possible collaboration topics across the global strong-motion community.

Conference Paper↗

Water erosion on mars and its biologic implications

The Martian surface shows abundant evidence of water erosion. Liquid water is unstable under present climatic conditions but conditions may have been different in the past. The planet has been volcanically active throughout its history. The combination of water and volcanism must have commonly resulted in hydrothermal environments similar to those in which grow the most primitive terrestrial life-forms.

Endeavour↗