: This report describes the concept for a geographical information system (GIS) that can infer subsurface geology and material properties. The hypotheses were that a GIS can be programmed to 1) follow the fundamental logic sequence developed for traditional terrain- and image-analysis procedures to infer geologic materials; 2) augment that sequence with correlative geospatial data from a variety of sources; and 3) integrate the inferences and data to develop best-guess estimates. Structured logic trees were developed to guide a terrain analyst through an interactive, geologic analysis based on querying and mentoring logic primarily using imagery and map data as input. The logic trees allow a terrain analyst with limited geology background and experience to rapidly infer the most likely geologic material. A new surface projection method was also developed to estimate depth to bedrock, and an existing method to determine depth to the water table was significantly expanded. The concept was proven to be feasible during blind evaluations conducted at Camp Grayling, MI, a cool, temperate, vegetation-covered site, and at Yuma Proving Ground, AZ, and Fort Irwin, CA, both hot, arid, barren sites. The results show that an analyst can infer the correct geologic conditions 70 80% of the time using these inferential methods.

Heat, fresh- and sea-water balances indicate that the late-summer rate of submarine melting at the terminus of tidewater LeConte Glacier, Alaska, U.S.A., in 2000 was about 12 in d(-1) w.e., averaged over the submerged face. This is 57 % of the estimated total ice loss at the terminus (calving plus melting) at this time. Submarine melting may thus provide a significant contribution to the overall ablation of a tidewater glacier. Oceanographic measurements (conductivity-temperature-depth) made 200-500 in from the terminus identified an isohaline (27 ppt) and isothermal (7.2degreesC) layer extending from 130 in depth to the fjord floor. Capping this is a 40 in thick overflow plume, distinguished by high outflow rates, low salinity (22-25 ppt) and lower temperatures (5-6degreesC). Mixing models indicate that fresh water comprised about 11 % of this plume; it originates mostly as subglacial discharge whose buoyancy drives convection at the terminus. Deep, warm saline waters are incorporated into the plume as it ascends, causing substantial melting of ice along the submarine face. The calving terminus undergoes seasonal changes that coincide with changes in subglacial discharge and fjord water temperatures, and we suggest that these fluctuations in terminus position are directly related to changes in submarine melting.

Abstract In August 2000, we used cross-borehole ground penetrating radar (GPR) measurements to investigate sites on Fort Wainwright, Alaska, and east of the Cold Regions Research and Engineering Laboratory (CRREL) permafrost tunnel near Fox, Alaska. The sites are characterized by perennially frozen soils characteristic of much of interior Alaska. The purpose of this investigation was to define variations in GPR signal velocity and attenuation that may be indicative of hydrocarbon contamination and to determine if downhole GPR methods could detect petroleum contaminants. To acquire background information for comparison, we conducted detailed investigations in non-contaminated areas to define general conditions before we profiled at the Fort Wainwright Tank Farm where extensive contamination has been documented. Results showed that cross-borehole GPR is a useful tool for detecting changes in electrical characteristics in permafrost and contaminated environments. Bulk electrical properties (velocity and attenuation) were observed to vary systematically between frozen and unfrozen materials, and produced distinct signal responses to frozen/unfrozen sediments, bedrock and massive ground ice. There is considerable overlap in both velocity and attenuation for soils and rock. Fine-grained silts exhibit higher attenuation (9–10 dB m−1) than coarser sand and gravel (1.5–2 dB m−1). Bedrock values are intermediate (2–7 dB m−1). Unfrozen sediment and rock exhibit velocities between 0.05 m ns−1 and 0.1 m ns−1 and attenuation ranges from 4 dB m−1 to 11 dB m−1 at 100 Mhz while frozen materials are between the velocities of 0.1 m ns−1 and 0.18 m ns−1 and 1.5 dB m−1 and 10 dB m−1 at −0.3 °C. The general trend is for frozen materials to have higher velocities than their unsaturated or saturated counterparts. Preliminary results where petroleum contamination was pervasive show that the attenuation decreases from 6 dB m−1 to 7 dB m−1 in uncontaminated schist to 4 dB m−1 in the hydrocarbon-contaminated schist. Additional measurements are required to determine that the observed decrease in attenuation is primarily related to petroleum contamination.

: The glacial stratigraphy of Fort Richardson reflects deposition in glacial and glacial-marine environments during multiple retreat phases following the last glacial maximum. A preliminary model relied heavily on the glacial history off the region, mapping by the U.S. Geological Survey, and limited borehole logs. This report expands on that model and describes new subsurface data obtained from field observations and descriptions of stratigraphic exposures and core samples from 28 new boreholes between 1997 and 1998. Geophysical techniques were applied to seven of the new boreholes and 25 existing monitoring wells, augmenting surface techniques (ground resistivity and ground penetrating radar). Beneath the cantonment is a thick unconfined aquifer, apparently deposited as a large alluvial fan (Mountain View fan), that overlies a fine-grained confining layer composed of mud and diamicton. The diamicton is a subglacial lodgement deposit bracketed by stratified debris flow deposits, being thickest to the southeast, dipping and thinning to the north and west where deposits of the Mountain View fan truncate the confining horizon, providing potential hydraulic communication between the tipper (unconfined) and lower (confined) aquifers. A second mud-diamicton horizon forms a deeper (38-66 m depth) confining layer and also appears to extend across the cantonment. Between the upper and lower confining diamicton horizons are coarse, sandy gravels that make up a confined aquifer. Ground water in the unconfined aquifer flows generally to the northwest, presumably recharged by Ship Creek. When ground water levels are low (i.e., winter), flow is locally diverted by irregularities in the surface of the upper confining layer. When recharge is high, regional flow is unaffected by these irregularities. Ground water in the confined aquifer also flows to the northwest, following the slope of the potentiometric surface.

: Eagle River Flats (ERF) is a subarctic estuarine salt marsh where human and natural forces are causing significant changes in the environment. Multiple internal and external forces govern the physical and chemical processes by actively altering surface conditions, sometimes in unpredictable ways. ERF is also used as an artillery range by the U.S. Army, where past use has resulted in white phosphorous (WP) contamination of the sediments within ponds and mudflats. Bottom-feeding waterfowl ingest this WP, which causes rapid death. This report documents analyses of the physical environment, describing the nature of the physical systems and factors controlling them. It includes data on sedimentation, erosion and hydrology. These investigations provide knowledge necessary to designing and evaluating remedial technologies. They also help determine the system's capacity to naturally attenuate the WP contamination.

: This report describes the results of investigations into the role of tidal flat physical systems in the natural attenuation of white phosphorus (WP) contamination in Eagle River Flats (ERF) on Fort Richardson, Alaska. Waterfowl feeding in ponds and marshes here ingest the WP and die. These investigations found that natural attenuation and in-situ degradation of the WP could result from certain physical phenomena operating within the EFF ecosystem. Specifically, the on-going erosion and headward recession in the gullies will drain large areas of contaminated ponds in an estimated 1 to 10 years. Lowering of water levels should lead to in-situ WP degradation and natural attenuation as pond sediments dry. Annual sedimentation rates in some ponds and marshes are sufficient to bury WP in several years or more and thereby reduce the exposure to feeding waterfowl. Ice and water are also effective transporters of WP, moving it about ERF and into Eagle River and eventually into Knik Arm where its fate is unknown. Certain areas of ERF will require artificial drainage, but natural conditions can be restored following treatment. Recommendations are made for the use of natural attenuation and additional studies that are required to ensure the successful clean-up of ERF.