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At least 19 recordsLinked to original sources
USGS2023

60 years and beyond of Reviews of Geophysics

Reviews of Geophysics is an AGU journal, first established in February 1963. It is a hybrid open access invitation-only journal that publishes comprehensive review articles across various disciplines within the Earth and Space Sciences. The selection criteria are rigorous and many submissions are declined without review. The journal is the highest ranked in the fields of Geochemistry and Geophysics, with a high Journal Impact Factor (JIF 2021 = 24.9), which is indicative of its high visibility and influence within the scientific community. The journal's published review papers, beyond a mere summary of literature, provide crucial context for current work, and establish the framework for comprehensive understanding of research progress, challenges, and interconnections between different communities, so that research may be appreciated by a broad audience. We emphasize the importance of publishing studies that provide a comprehensive overview and synthesis of the current state of knowledge in a field, especially in the case of geophysics, where knowledge is rapidly developing, increasing and becoming more specialized.

Reviews of Geophysics↗
USGS2008

Advancing process‐based watershed hydrological research using near‐surface geophysics: A vision for, and review of, electrical and magnetic geophysical methods

We want to develop a dialogue between geophysicists and hydrologists interested in synergistically advancing process based watershed research. We identify recent advances in geophysical instrumentation, and provide a vision for the use of electrical and magnetic geophysical instrumentation in watershed scale hydrology. The focus of the paper is to identify instrumentation that could significantly advance this vision for geophysics and hydrology during the next 3–5 years. We acknowledge that this is one of a number of possible ways forward and seek only to offer a relatively narrow and achievable vision. The vision focuses on the measurement of geological structure and identification of flow paths using electrical and magnetic methods. The paper identifies instruments, provides examples of their use, and describes how synergy between measurement and modelling could be achieved. Of specific interest are the airborne systems that can cover large areas and are appropriate for watershed studies. Although airborne geophysics has been around for some time, only in the last few years have systems designed exclusively for hydrological applications begun to emerge. These systems, such as airborne electromagnetic (EM) and transient electromagnetic (TEM), could revolutionize hydrogeological interpretations. Our vision centers on developing nested and cross scale electrical and magnetic measurements that can be used to construct a three‐dimensional (3D) electrical or magnetic model of the subsurface in watersheds. The methodological framework assumes a ‘top down’ approach using airborne methods to identify the large scale, dominant architecture of the subsurface. We recognize that the integration of geophysical measurement methods, and data, into watershed process characterization and modelling can only be achieved through dialogue. Especially, through the development of partnerships between geophysicists and hydrologists, partnerships that explore how the application of geophysics can answer critical hydrological science questions, and conversely provide an understanding of the limitations of geophysical measurements and interpretation.

Hydrological Processes↗
USGS2012

A review of the regional geophysics of the Arizona Transition Zone

A review of existing geophysical information and new data presented in this special section indicate that major changes in crustal properties between the Basin and Range and Colorado Plateau occur in, or directly adjacent to, the region defined as the Arizona Transition Zone. Although this region was designated on a physiographic basis, studies indicate that it is also the geophysical transition between adjoining provinces. The Transition Zone displays anomalous crustal and upper mantle seismic properties, shallow Curie isotherms, high heat flow, and steep down-to-the-plateau Bouguer gravity gradients. Seismic and gravity studies suggest that the change in crustal thickness, from thin crust in the Basin and Range to thick crust in the Colorado Plateau, may occur as a series of steps rather than a planar surface. Anomalous P wave velocities, high heat flow, shallow Curie isotherms, and results of gravity modeling suggest that the upper mantle is heterogeneous in this region. A relatively shallow asthenosphere beneath the Basin and Range and Transition Zone contrasted with a thick lithosphere beneath the Colorado Plateau would be one explanation that would satisfy these geophysical observations.

Journal of Geophysical Research↗
USGS1999

Crustal and lithospheric structure of the west Antarctic Rift System from geophysical investigations: A review

The active West Antarctic Rift System, which extends from the continental shelf of the Ross Sea, beneath the Ross Ice Shelf and the West Antarctic Ice Sheet, is comparable in size to the Basin and Range in North America, or the East African rift systems. Geophysical surveys (primarily marine seismic and aeromagnetic combined with radar ice sounding) have extended the information provided by sparse geologic exposures and a few drill holes over the ice and sea covered area. Rift basins developed in the early Cretaceous accompanied by the major extension of the region. Tectonic activity has continued episodically in the Cenozoic to the present, including major uplift of the Transantarctic Mountains. The West Antarctic ice sheet, and the late Cenozoic volcanic activity in the West Antarctic Rift System, through which it flows, have been coeval since at least Miocene time. The rift is characterized by sparse exposures of late Cenozoic alkaline volcanic rocks extending from northern Victoria Land throughout Marie Byrd Land. The aeromagnetic interpretations indicate the presence of > 5 x 105 km2 (> 106 km3) of probable late Cenozoic volcanic rocks (and associated subvolcanic intrusions) in the West Antarctic rift. This great volume with such limited exposures is explained by glacial removal of the associated late Cenozoic volcanic edifices (probably hyaloclastite debris) concomitantly with their subglacial eruption. Large offset seismic investigations in the Ross Sea and on the Ross Ice Shelf indicate a ~ 17-24-km-thick, extended continental crust. Gravity data suggest that this extended crust of similar thickness probably underlies the Ross Ice Shelf and Byrd Subglacial Basin. Various authors have estimated maximum late Cretaceous-present crustal extension in the West Antarctic rift area from 255-350 km based on balancing crustal thickness. Plate reconstruction allowed < 50 km of Tertiary extension. However, paleomagnetic measurements suggested about 1000 km of post-middle Cretaceous translation between East Antarctica and Pacific West Antarctica. Because a great amount of crustal extension in late Cenozoic time is unlikely, alternate mechanisms have been proposed for the late Cenozoic volcanism. Its vast volume and the ocean island basalt chemistry of the exposed late Cenozoic alkaline volcanic rocks were interpreted as evidence for a mantle plume head. An alternative or supplemental explanation to the mantle plume hypothesis is significantly greater lower lithosphere (mantle) stretching resulting in greater decompression melting than the limited Cenozoic crustal extension allows. Because of very slow rates of late Cenozoic extension in the West Antarctic Rift System, the amount of advected heat is small compared with the conductive heat. Therefore, phase transition probably would not explain the large subsidence with low extension observed in the West Antarctic Rift System.

Global and Planetary Change↗
USGS2026

Computational electromagnetic geophysics for groundwater system studies: A review on established practices and recent advances

Identifying effective solutions for locating groundwater resources and ensuring the quality of drinking water is increasingly urgent, given the challenges posed by climate change and population growth. This review investigates electromagnetic geophysical imaging techniques, in both time- and frequency-domain, that can provide valuable insights for groundwater assessment. We explore computational electromagnetic methods used to evaluate electromagnetic data and several recent hydrogeophysical case studies. As open-source frameworks for modeling electromagnetic geophysical problems become available, a broader range of researchers can interpret their data with computationally advanced software. We provide an overview of documented open-source codes for evaluating electromagnetic data and analyze various hydrological targets in relation to their electromagnetic surveying technique and the computational method applied. Furthermore, we evaluate the potential of advanced computational techniques, including three-dimensional modeling, non-deterministic inversion and machine learning, to couple geophysical with numerical groundwater modeling and apply it in groundwater system studies. Despite obstacles such as complexity and resource demands, our findings indicate that the quantification and integration of predictive uncertainties from both electromagnetic and hydrological data and simulations would significantly improve the reliability of hydrogeophysical models. This can lead to a deeper understanding of groundwater systems and improved management practices.

Journal of Hydrology↗
USGS2022

Northern Cascadia Margin gas hydrates — Regional geophysical surveying, IODP drilling leg 311, and cabled observatory monitoring

This article reviews extensive geophysical survey data, ocean drilling results and long-term seafloor monitoring that constrain the distribution and concentration of gas hydrates within the accretionary prism of the northern Cascadia subduction margin, located offshore Vancouver Island in Canada. Seismic surveys and geologic studies conducted since the 1980s have mapped the bottom simulating reflector (BSR), detected gas hydrate occurrence and estimated gas hydrate and free gas concentrations. Additional constraints were obtained from seafloor-towed, controlled-source electromagnetic surveying. A component of these studies has been the examination of low-temperature seafloor vents and seeps that emit gas and fluids into the ocean. These features are identified seismically as chimney-like zones of reduced acoustic reflectivity within the sediment stratigraphy, functioning as conduits for gas and fluid migration from below the BSR to the seafloor. Gas hydrates have been recovered from the seafloor and from sediment cores at vent sites, mostly in massive (nodular) form and as a vein-like fracture filling. The Ocean Networks Canada cabled NEPTUNE observatory has gathered extensive continuous, long-term observations on gas hydrate dynamics at the seafloor and in boreholes at two nodes on the continental slope featuring high gas hydrate concentrations. Measurements taken at the observatory include a time-series of gas bubble emission rates, changes in the near-seafloor electromagnetic structure and seafloor compliance linked to gas hydrate formation and dissociation. Two Integrated Ocean Drilling Program (IODP) expeditions collected cores, measured downhole properties and deployed downhole instruments within the central accretionary prism. At IODP Site U1364, pore pressures are being monitored above and below the base of the gas hydrate stability zone at a slope setting using an “Advanced Circulation Obviation Retrofit Kit” (A-CORK). Downhole pore pressures, temperatures and electrical resistivities also are being monitored at IODP Site U1416 using the “Simple Cabled Instrument for Measuring Parameters In Situ” (SCIMPI) tool at a vent site from near-seafloor to just above the base of the gas hydrate stability zone.

British Columbia↗
USGS2023

Hydrogeologic characterization of Area B, Fort Detrick, Maryland

Groundwater in the karst groundwater system at Area B of Fort Detrick in Frederick County, Maryland, is contaminated with chlorinated solvents from the past disposal of laboratory wastes. In cooperation with U.S. Army Environmental Command and U.S. Army Garrison Fort Detrick, the U.S. Geological Survey performed a 3-year study to refine the conceptual model of groundwater flow in and around Area B of Fort Detrick at the site- to regional-scale. The investigation was designed to review the geologic setting, assess the temporal variability of the hydrologic system, evaluate the potential for interbasin groundwater flow, determine the degree of vertical connectivity of the aquifer, characterize the sources and timing of groundwater recharge, and identify if dyes from previous tracer tests continue to drain from the aquifer. This study established a continuous hydrologic monitoring network of 12 water level gages, 2 streamgages, a precipitation gage, and in situ fluorometric monitoring. A water budget analysis was performed using hydrologic monitoring data and a soil-water balance model constructed for the study. In this study each individual water budget term is calculated using available data or through modeling, and a water budget residual term is calculated. If the water budget residual term is small relative to the uncertainty of the underlying data, then an additional import or export of water (in other words, interbasin transfer) is not needed to fully describe the hydrologic system. Groundwater and spring samples from 20 locations were collected in a 2019 synoptic geochemical sampling event and analyzed for a suite of analytes that included groundwater age tracer constituents. The karst groundwater system was found to be highly responsive to hydrologic events, with strong water level and stream base flow responses to individual storm events and a historic wet period in 2017 and 2018. The water budget analysis included historic flooding in May 2018, though more typical hydrologic patterns were observed in 2019 and 2020. During most evaluated intervals, the water budget residual was less than the estimated uncertainty on the residual for the two Carroll Creek watersheds, which suggested no substantial net interbasin flow occurs from these watersheds. The watershed difference area, a region that includes Area B, had a significant negative water budget residual, which may be the result of a net interbasin import of groundwater or the result of focused groundwater recharge not simulated by the soil-water balance model. Geochemical analysis and groundwater age dating reveals shallow groundwater (approximately less than [<] 150 feet deep) appears to be relatively young (approximately <30 years) and to be recharged in the vicinity of Area B. In the deep groundwater sampled in this study (approximately greater than [>] 150 feet deep), older groundwater from a differing recharge source, based on stable isotopes and noble gas analyses, is observed and interpreted to represent less direct connectivity to the surface and increased proportions of water recharged to the north and (or) west of Area B. A clustering analysis to reveal groupings within the suite of geochemical data was used to define seven groups. The groupings generally show that wells in similar depths and lateral aquifer positions generally cluster together, with some exceptions. Although limited by suspended sediments, the in situ fluorometric monitoring at springs did not detect any dye leaving the system above the limit of detection for the method. Dye was only detected above the limit of detection in one well, which was used as an injection well during a previous dye tracer test. The results of this study support and refine the conceptual site model of groundwater hydrology at Area B. The geologic and geophysical log review in this study agrees with prior assessments of physical controls on groundwater flow. A literature review of mid-Atlantic karst studies identified similar controls reported in these environments. The additional characterization of hydrologic responsiveness in this study suggests that hydrologic conditions and events are important considerations when interpreting potentiometric surfaces and contaminant trends over time and highlights the importance of continuous hydrologic monitoring. There is evidence to suggest that either intense focused groundwater recharge occurs in the vicinity of Area B or net along-valley groundwater interbasin flow from the upper study watershed enters the lower watershed and discharges to Carroll Creek. Geochemical analyses also suggest that water recharged from Catoctin Mountain and the elevated areas to the north and (or) west of the site may be present in the older and deeper Area B groundwater.

Maryland↗
USGS2001

Evolution of the conceptual model of unsaturated zone hydrology at Yucca Mountain, Nevada

Yucca Mountain is an arid site proposed for consideration as the United States’ first underground high-level radioactive waste repository. Low rainfall (approximately 170 mm/yr) and a thick unsaturated zone (500–1000 m) are important physical attributes of the site because the quantity of water likely to reach the waste and the paths and rates of movement of the water to the saturated zone under future climates would be major factors in controlling the concentrations and times of arrival of radionuclides at the surrounding accessible environment. The framework for understanding the hydrologic processes that occur at this site and that control how quickly water will penetrate through the unsaturated zone to the water table has evolved during the past 15 yr. Early conceptual models assumed that very small volumes of water infiltrated into the bedrock (0.5–4.5 mm/yr, or 2–3 percent of rainfall), that much of the infiltrated water flowed laterally within the upper nonwelded units because of capillary barrier effects, and that the remaining water flowed down faults with a small amount flowing through the matrix of the lower welded, fractured rocks. It was believed that the matrix had to be saturated for fractures to flow. However, accumulating evidence indicated that infiltration rates were higher than initially estimated, such as infiltration modeling based on neutron borehole data, bomb-pulse isotopes deep in the mountain, perched water analyses and thermal analyses. Mechanisms supporting lateral diversion did not apply at these higher fluxes, and the flux calculated in the lower welded unit exceeded the conductivity of the matrix, implying vertical flow of water in the high permeability fractures of the potential repository host rock, and disequilibrium between matrix and fracture water potentials. The development of numerical modeling methods and parameter values evolved concurrently with the conceptual model in order to account for the observed field data, particularly fracture flow deep in the unsaturated zone. This paper presents the history of the evolution of conceptual models of hydrology and numerical models of unsaturated zone flow at Yucca Mountain, Nevada (Flint, A.L., Flint, L.E., Kwicklis, E.M., Bodvarsson, G.S., Fabryka-Martin, J.M., 2001. Hydrology of Yucca Mountain. Reviews of Geophysics in press). This retrospective is the basis for recommendations for optimizing the efficiency with which a viable and robust conceptual model can be developed for a complex site.

Nevada↗
USGS2022

Achievements and prospects of global broadband seismographic networks after 30 years of continuous geophysical observations

Global seismographic networks (GSNs) emerged during the late nineteenth and early twentieth centuries, facilitated by seminal international developments in theory, technology, instrumentation, and data exchange. The mid- to late-twentieth century saw the creation of the World-Wide Standardized Seismographic Network (1961) and International Deployment of Accelerometers (1976), which advanced global geographic coverage as seismometer bandwidth increased greatly allowing for the recording of the Earth's principal seismic spectrum. The modern era of global observations and rapid data access began during the 1980s, and notably included the inception of the GEOSCOPE initiative (1982) and GSN (1988). Through continual improvements, GEOSCOPE and the GSN have realized near-real time recording of ground motion with state-of-art data quality, dynamic range, and timing precision to encompass 180 seismic stations, many in very remote locations. Data from GSNs are increasingly integrated with other geophysical data (e.g., space geodesy, infrasound and Interferometric Synthetic Aperture Radar). Globally distributed seismic data are critical to resolving crust, mantle, and core structure; illuminating features of the plate tectonic and mantle convection system; rapid characterization of earthquakes; identification of potential tsunamis; global nuclear test verification; and provide sensitive proxies for environmental changes. As the global geosciences community continues to advance our understanding of Earth structure and processes controlling elastic wave propagation, GSN infrastructure offers a springboard to realize increasingly multi-instrument geophysical observatories. Here, we review the historical, scientific, and monitoring heritage of GSNs, summarize key discoveries, and discuss future associated opportunities for Earth Science.

Reviews of Geophysics↗
USGS1980

A summary report of the regional geology, petroleum potential, environmental geology, and operational considerations in the area of proposed lease sale No. 68, offshore southern California

This report reviews geological, geophysical and technological data that are pertinent to proposed OCS Lease Sale 68. Under consideration are 26,000 mi 2 (67,400 km 2 ) of the California Continental Borderland north of the U.S.-Mexico boundary. The area includes both leased and unleased tracts and lies adjacent to the highly productive coastal basins of southern California. Factors that have contributed to petroleum generation in the onshore basins, such as thickness, burial depth and hydrocarbon content, are less favorable in parts of the offshore region. Nevertheless, regional geologic and geophysical mapping together with data from stratigraphic test wells and bottom samples suggest that source beds, reservoir rocks and traps are present beneath the borderland. Strata of Miocene age are widespread within the area of proposed OCS Lease Sale 68 and contain fair to excellent potential source rocks. Eocene and early Miocene sandstone beds in the Cortes Bank test well and late Miocene and Pliocene rocks in the Point Conception test well have porosities that are within the range of good reservoir rocks. Late middle Miocene through Pliocene sandy turbidites of reservoir quality possibly occur in some outer borderland basins. Additional prospective targets are fractured Miocene shale beds that may be present in the deeper basins and on the down-flank margins of major uplifts. Numerous structural and stratigraphic traps, which formed in response to late Cenozoic wrench tectonics, are distributed throughout the borderland.

California↗
USGS1980

A summary report of the regional geology, environmental geology, OCS resource appraisal, petroleum potential, and operational considerations in the area of proposed lease sale 73, offshore California

This report reviews geological, geophysical and technological data pertinent to proposed Lease Sale 73. Under consideration is the entire continental margin of California that is bounded on the west by the 2500 meter isobath. This area encompasses the whole of the southern California Borderland, the continental shelves of central and northern California, and the upper part of the continental slope from Mexico on the south to Oregon on the north. The area includes both leased and unleased tracts and lies adjacent to highly productive coastal basins of central and northern California . Because the geology of the south and north parts of this large area differ, they are considered separately in this report.

California↗
USGS1985

Remote sensing; a geophysical perspective

In this review of developments in the field of remote sensing from a geophysical perspective, the subject is limited to the electromagnetic spectrum from 0.4 mu m to 25 cm. Three broad energy categories are covered: solar reflected, thermal infrared, and microwave.The reflected solar region has been the most intensely studied. Photointerpretation of images from individual spectral bands or from color composites remains the most widely used method of analysis. New instrumentation and digital processing, based on analysis of laboratory and field spectra, provide significant advances that are beginning to be applied to resource exploration. Color compositing techniques have been effectively used to detect the characteristic spectral reflectance features of iron oxides and hydroxyl-bearing materials in satellite multispectral data for mapping areas of hydrothermal alteration. Airborne spectrometers can now detect individual spectral features of many minerals which are diagnostic of different stages of hydrothermal alteration. Evolution was from discrimination, based on empirical experience, to mineralogic identification and leading to quantification. Current developments also indicate new, promising extensions to vegetated terrains.Advances in thermal infrared studies are due to development of thermal models that permit mapping of physical property variations and to detection of spectral differences that provide important compositional information. Analysis techniques are still in their infancy, and thermal satellite data remain appropriate only for regional investigations.Microwave data have been acquired mainly with radar systems, which can provide very high resolution from space, but use of textural and slope information has had limited application. Long-wavelength radiation has been shown to penetrate dry materials, and this may be applicable in extremely arid regions.

Geophysics↗
USGS1999

Geophysical framework of the southwestern Nevada volcanic field and hydrogeologic implications

Gravity and magnetic data, when integrated with other geophysical, geological, and rock-property data, provide a regional framework to view the subsurface geology in the southwestern Nevada volcanic field. The region has been loosely divided into six domains based on structural style and overall geophysical character. For each domain, the subsurface tectonic and magmatic features that have been inferred or interpreted from previous geophysical work has been reviewed. Where possible, abrupt changes in geophysical fields as evidence for potential structural lithologic control on ground-water flow has been noted. Inferred lithology is used to suggest associated hydrogeologic units in the subsurface. The resulting framework provides a basis for investigators to develop hypotheses from regional ground-water pathways where no drill-hole information exists.

Nevada↗
USGS2002

Abstracts of the annual meeting of Planetary Geologic Mappers: June 21-22, 2002, Tempe, Arizona

The annual meeting of planetary geologic mappers allows mappers the opportunity to exchange ideas, experiences, victories, and problems. In addition, presentations are reviewed by the Geologic Mapping Subcommittee (GEMS) to provide input to the Planetary Geology and Geophysics Mapping Program review panel’s consideration of new proposals and progress reports that include mapping tasks. Funded mappers bring both oral presentation materials (slides or viewgraphs) and map products to post for review by GEMS and fellow mappers. Additionally, the annual meetings typically feature optional field trips that offer Earth analogs and parallels to planetary mapping problems or workshops that provide information and status of current missions. The 2002 meeting of planetary geologic mappers was held June 21-22 at the Mars Flight Facility, Arizona State University, Tempe, Arizona. Dr. Phil Christensen graciously offered the use of the newly renovated facility, and Ms. Kelly Bender not only proved to be a courteous hostess, but also arranged a short workshop on June 23 regarding TES and THEMIS data. Approximately 30 people attended each day of the 2-day meeting, although not the same 30—some attended only on Thursday and others only on Friday. On Thursday, eight mappers gave oral presentations of Mars mapping, and an additional two presentations were presented as posters only. Eight oral presentations on Venus mapping were given on Friday, and an additional four presentations were posters only. Twelve people attended the TES/THEMIS workshop. Presentations of Ganymede mapping and Europa mapping (the latter not yet financially sponsored by PG&G mapping program) were also given on Friday. Aside from the regular presentations of maps-in-progress, there were some additional talks. Lisa Gaddis (USGS) presented a proposal seeking support for a new lunar mapping program in light of all the new data available; she made a good case that the GEMS panel discussed. Jim Skinner (USGS) gave a short presentation on free (or nearly so) software available for 3D viewing of planetary surfaces. Healthy discussions focused on the review time for some maps and the use of different styles of correlation charts observed on the presented maps. Next year’s meeting will be held June 19-20 at Brown University, Providence, RI.

Open-File Report↗
USGS2002

Abstracts of the annual Planetary Geologic Mappers Meeting, June 18-19, 2001, Albuquerque, New Mexico

The annual Planetary Geologic Mappers Meeting serves two purposes. In addition to giving mappers the opportunity to exchange ideas, experiences, victories, and problems with others, presentations are reviewed by the Geologic Mapping Subcommittee (GeMS) to provide input to the Planetary Geology and Geophysics Mapping Program review panel’s consideration of new proposals and progress reports that include mapping tasks. Funded mappers bring both oral presentation materials (slides or viewgraphs) and map products to post for review by GeMS and fellow mappers. Additionally, the annual meetings typically feature optional field trips offering earth analogs and parallels to planetary mapping problems. The 2001 Mappers Meeting, June 18-19, was convened by Tim Parker, Dave Senske, and Ken Tanaka and was hosted by Larry Crumpler and Jayne Aubele of the New Mexico Museum of Natural History and Science in Albuquerque, New Mexico. Oral presentations were given in the Museum’s Honeywell Auditorium, and maps were posted in the Sandia Room. In addition to active mappers, guests included local science teachers who had successfully competed for the right to attend and listen to the reports. It was a unique pleasure for mappers to have the opportunity to interact with and provide information to teachers responding so enthusiastically to the meeting presentation. On Sunday, June 17, Larry and Jayne conducted an optional pre-meeting field trip. The flanks of Rio Grande Rift, east and west of Albuquerque and Valles Caldera north of town presented tectonic, volcanic, and sedimentary examples of the Rift and adjoining areas analogous to observed features on Mars and Venus. The arid but volcanically and tectonically active environment of New Mexico’s rift valley enables focus on features that appear morphologically young and spectacular in satellite images and digital relief models. The theme of the trip was to see what, at orbiter resolution, "obvious" geologic features look like at lander (outcrop) scales. Trips to the top of the rift-flanking mountains (Sandia Peak, 10,600 ft) and the Valles Caldera, as well as various active spring deposits highlighted the day. After welcoming remarks from the host, Larry Crumpler, opening remarks by Tim Parker and Dave Senske and a report on mapping program status by Ken Tanaka, the mappers’ oral presentations began the morning of June 18, with a session on Venus Geologic Mapping. The afternoon continued with an exciting USGS Planetary GIS on the Web (PIGWAD) demonstration and ended with an open discussion of issues in planetary mapping. Posted maps of Venus quadrangles were viewed during the morning break. Tuesday’s Mars Geologic Mapping session began with a pep talk from Tim Parker encouraging mapping community input to the MER landing site selection committee and continued with Steve Saunders describing the potential contribution of Odyssey Mission data to the geologic mapping of Mars. A Mars map poster session was held during the morning break, and the meeting was adjourned mid-afternoon. After the mappers meeting on Tuesday, attendants were treated to a "Field trip to Mars." The Institute of Meteoritics at the University of New Mexico houses an outstanding collection of meteorites, including those that have been identified as originating from Mars. The Institute tour featured examples of most of the different lithologies exhibited by martian meteorites identified to date, as well as some of the analytical tests (scanning electron microscope) they are conducting on specimens from ALH84001. Wednesday, June 20, featured an optional post-meeting field trip to see a travertine quarry and nearby sites of travertine deposition, the Very Large Array near Socorro, and other volcanic features within the Rio Grande Rift.

New Mexico↗