Filters: Tags: MONITORING 5-PHYSICAL SCIENCE (X)348 results (131ms)
Monitoring Geohazards near Pipeline Corridors with an Advanced InSAR Technique and Geomechanical Modelling
Active and Potentially Active Faults in Or Near the Alaska Highway Corridor, Dot Lake to Tetlin Junction, Alaska
In 2005 the Alaska Division of Geological & Geophysical Surveys initiated a multi-year geologic field study focused on a corridor centered along the Alaska Highway between Delta Junction and the Canada border. The purpose of this project is to provide geologic information relevant to a proposed Alaska-Canada natural gas pipeline and other future development in the corridor. Identification of active faults and characterization of seismic hazards were included in the project. During the 2006 and 2007 field seasons, lineaments and geologic features indicative of possible youthful surface faulting in or near the western half of the corridor between Delta Junction and Dot Lake were identified and evaluated. Four of the...
Regional baseline geochemistry and environmental effects of gold placer mining operations on the Fortymile River, eastern Alaska
A systematic water-quality study of the Fortymile River and many of its major tributaries in eastern Alaska was conducted in June of 1997 and 1998. Surface-water samples were collected for chemical analyses to establish regional baseline geochemistry values and to evaluate the possible environmental effects of suction-dredge placer gold mining and bulldozer-operated placer gold mining (commonly referred to as “cat mining”). In general, the water quality of the Fortymile River is very good, with low total dissolved solids and only two cases in which the concentration of any element exceeded primary or secondary drinking-water quality standards. In both cases, iron exceeded secondary drinking-water limits. At...
The Geochemistry of Three Tin-Bearing Skarns and Their Related Plutonic Rocks, Atlin, Northern British Columbia
The Late Cretaceous Surprise Lake batholith in the Atlin district of northern British Columbia is a highly differentiated, fluoritic, and peraluminous subalkaline body of adamellite-granite composition. The presence of miarolitic cavities and chilled, fine-grained margins suggests it was emplaced at a high structural level, and its trace element signature indicates it has some within-plate granitoid characteristics. The batholith shows many chemical similarities to the I-type igneous rocks associated with W skarns in British Columbia, although it averages >2,700 ppm F, whereas plutons related to W skarns average <400 ppm F. It also shares similar characteristics to the Seagull batholith in south-central Yukon which,...
Variations in late Quaternary wind intensity from grain-size partitioning of loess deposits in the Nenana River Valley, Alaska
A high-resolution column of 57 loess samples was collected from the Dry Creek archaeological site in the Nenana River Valley in central Alaska. Numerical grain-size partitioning using a mixed Weibull function was performed on grain-size distributions to obtain a reconstructed record of wind intensity over the last ~15,000 yr. Two grain-size components were identified, one with a mode in the coarse silt range (C1) and the other ranging from medium to very coarse sand (C2). C1 dominates most samples and records regional northerly winds carrying sediment from the Nenana River. These winds were strong during cold intervals, namely, the Carlo Creek glacial readvance (14.2–14 ka), a late Holocene Neoglacial period (4.2–2.7...
Analyses of Historic U.S. Bureau of Mines Samples for Geochemical Trace-Element and Rare-Earth-Element Data from the Ray River Watershed, and Kanuti and Hodzana Rivers Uplands, Central Alaska
The article discusses the analysis of geochemical samples from the Geological Survey and Bureau of Mines (USBM) by the Alaska Division of Geological & Geophysical Surveys (DGGS). Topics included are the evaluation of Strategic and Critical Minerals (SCM) content of central Alaska Ray River watershed specimen, the documentation of location coordinates and pulp preparation methodology, and the analysis of rare earth and ore elements by ALS Minerals Laboratories.
Flank collapse at Mount Wrangell, Alaska, recorded by volcanic mass-flow deposits in the Copper River lowland
Quaternary glacial, lacustrine, and fluvial interactions in the western Noatak basin, northwest Alaska
Characteristics of discontinuous permafrost based on ground temperature measurements and electrical resistivity tomography, southern Yukon, Canada
Cryostratigraphic mapping in the main shaft of the CRREL tunnel indicates secondary modification of original Pleistocene-age syngenetic permafrost. Layered, lenticular-layered and micro-lenticular cryostructures within undisturbed silt characterise the syngenetic permafrost. Thawed and refrozen deposits are characterised by massive and reticulate-chaotic cryostructures. The micro-morphology of typical cryostructures, as observed through an environmental scanning electron microscope (ESEM), is described. It is inferred that preferential cryogenic modification has occurred due to fluvio-thermal erosion operating along ice wedges. Soil and ice pseudomorphs are the manifestation of this process. Gravel, silt, ice and...
We measured the surface velocity field during the summers of 1999 and 2000 on the 7 km long, 185 m thick Bench Glacier, Alaska, USA. In the spring of both years, a short-lived pulse of surface velocity, 2-4 times the annual mean velocity, propagated up-glacier from the terminus at a rate of similar to 200-250 m d super(-1). Displacement attributable to rapid sliding is similar to 5-10% of the annual surface motion, while the high-velocity event comprised 60-95% of annual basal motion. Sliding during the propagating speed-up event peaked at 6-14 cm super(-1), with the highest rates in mid-glacier. Continuous horizontal and vertical GPS measurements at one stake showed divergence and then convergence of the ice surface...
Relations between water physico-chemistry and benthic algal communities in a northern Canadian watershed: defining reference conditions using multiple descriptors of community structure
Evidence of soil nutrient availability as the proximate constraint on growth of treeline trees: Reply
Composition and function of biological soil crust communities along topographic gradients in grasslands of central interior British Columbia (Chilcotin) and southwestern Yukon (Kluane)
The 2002 Mw 7.9 Denali Fault earthquake, Alaska, provides an unparalleled opportunity to investigate in quantitative detail the regional hillslope mass-wasting response to strong seismic shaking in glacierized terrain. We present the first detailed inventory of ∼1580 coseismic slope failures, out of which some 20% occurred above large valley glaciers, based on mapping from multi-temporal remote sensing data. We find that the Denali earthquake produced at least one order of magnitude fewer landslides in a much narrower corridor along the fault ruptures than empirical predictions for an M ∼8 earthquake would suggest, despite the availability of sufficiently steep and dissected mountainous topography prone to frequent...