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We evaluate potential tsunami hazards for several communities in lower Cook Inlet, including Anchor Point, Kenai, Ninilchik, and Tyonek, by numerically modeling the extent of inundation from tsunami waves generated by hypothetical earthquakes. We define an updated suite of earthquakes—including Tohoku-style megathrust ruptures and other sources in the eastern part of the Alaska–Aleutian megathrust—to calculate vertical seafloor displacements and model resulting tsunami dynamics. A hypothetical earthquake spanning from Kodiak Island to Prince William Sound with maximum slip distributed between depths of 5 and 22 km (3.1 and 13.7 mi) results in “worst case” tsunami inundation for all communities. If the tsunami arrives at high tide, the maximum predicted overland flow depths in the communities can reach up to 10 m (32.8 ft), and the currents could be as strong as 12 m/sec (23.4 knots). Dangerous wave activity is expected to last for more than 24 hours. Results presented here are intended to provide guidance to local emergency management agencies for tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami damage. [ABSTRACT FROM AUTHOR]

Observations of the 210 m (650) high York terrace and other wave-cut surfaces, the distribution of distinctive erratics, and the distribution and nature of both onshore and offshore sediments suggest that one or more high sea level stands are the primary control on Pleistocene landforms of the western Seward Peninsula. The widespread erratics of the region are thought to have been mobilized and dispersed by shore-ice racing and sea ice movements rather than by movement of glacial ice accumulations. Glaciers do not appear to have developed in the York Mountains and the few local surface features previously mapped as moraine are thought to be erratic accumulations, stream terrace deposits, or talus and landslide deposits. Pleistocene to Recent faulting likely contributed to some landform elevations and possibly to discontinuities in their present distribution. At the time of the high sea level stand that created the York terrace, the York Mountains would have been an island archipelago; a cape analogous to the present Cape Prince of Wales was present along the southwest bank of the York Mountains, and much of the area west of the York Mountains was below sea level and scoured by north-flowing currents. These currents appear to have removed bottom sediments, transported them northward, and deposited them in a shoal in the Chukchi Sea analogous to today's active Prince of Wales shoal. Cape Mountain would have been an isolated island at this time. The York terrace high sea level stand could have affected other parts of Seward Peninsula, such as the Pilgrim River gap (elevation of 60 m [200]). Flooding of this pass would have created a seaway between the estuary of the Niukluk River drainage and the now intertidal Imuruk Basin. Sea levels higher than those forming the York terrace seem to be indicated in some areas. This study synthesizes observations incidental to reconnaissance geologic investigations for other purposes and its principal interpretations and conclusions need to be more completely evaluated and tested. Hopefully, this report will help foster future investigations of the Pleistocene history of Seward Peninsula. [ABSTRACT FROM AUTHOR]

The article offers information on a study related to natural resources in the Western Cook Inlet region of Alaska conducted by the Alaska Division of Geological and Geophysical Surveys. Topics discussed include efforts to collect geological data for the petroleum system in the areas of Cook Inlet, information on papers showing migration of oil within the basin and, thickening of limestone deposits at the Bruin Bay fault.

As part of a study for a proposed hydropower facility, the authors conducted extensive field observations in the Upper Susitna basin, a 13,289 km2 (5,130 mi2) glacierized catchment in central Alaska, in 2012-2014. This comprehensive data set includes meteorological, glacier mass balance, snow cover, and soil measurements. We also include digitized snow depth data from a set of similar observations collected in the 1980s. The data will be useful for hydrological and glaciological studies, including modeling efforts. [ABSTRACT FROM AUTHOR]

The Annual Report from the Alaska Division of Geological & Geophysical Surveys provides information on the Geologic Hazards Section, which focuses on studying and responding to geologic processes that pose threats to lives and infrastructure in Alaska. The report discusses various programs and initiatives undertaken by the division, including assessing avalanche, earthquake, tsunami, and landslide hazards. The division collaborates with other organizations and uses data, modeling techniques, and mapping to improve preparedness, resilience, and public education regarding these natural hazards. The programs aim to provide accurate information and support decision-making for communities in Alaska. [Extracted from the article]

Strongly deformed marine terraces differ in their degree of development and preservation along 65 km of the coast between Fairweather Glacier and Icy Point in the Lituya Bay area of the eastern Gulf of Alaska. From Fairweather Glacier to Lituya Bay one prominent terrace flanks the coastal mountain front, and isolated remnants of a lower, younger terrace occur landward of a wide prograded coastal plain. From Lituya Bay to Crillon River a sequence of five well-developed terraces bevel the coastal foothills. From Finger Glacier to Icy Point four terraces and the possible remnants of a fifth occur. The terraces form an arch with an axis of maximum uplift near La Perouse Glacier. The deformation is progressively greater in the older terraces and shoreline angle relief on the highest terrace is 100 m or more. The terraces are of Pleistocene and Holocene age. The oldest terrace studied is not well dated but the next oldest may have formed during the post-Wisconsin sea level rise. The three Holocene terraces probably formed about 3,500 (3,990-2,960 cal yr BP), 1,000, and 500 years ago. Ongoing uplift and arching of the coastal zone may mark renewal of mid-Pleistocene folding, but Holocene uplift has taken place as discrete events that were probably accompanied by earthquakes. At least five uplift events have taken place between Lituya Bay and Icy Point in the past 3,000 to 4,000 years, which imply an average recurrence interval of ~500 years. Because recurrence of events that uplifted the terraces is distinctly longer than the average earthquake recurrence interval for the nearby Fairweather fault, coastal uplift may occur independently. The Finger Glacier fault displaces the Holocene terraces and may be a developing link between the onshore and offshore segments of the Fairweather fault. [ABSTRACT FROM AUTHOR]

Landslides are geologic hazards that threaten human lives, property, and infrastructure. Effective landslide threat mitigation requires identifying, inventorying, and studying landslides; developing a detailed landslide inventory map is the beginning of this process. Here we present the first landslide inventory map of parts of the Fairbanks North Star Borough (FNSB), Alaska, along with supporting data and a qualitative analysis of the results. This research was funded by the U.S. Geological Survey (USGS) EDMAP program, which funds universities to train the next generation of geologic mappers. The map and geodatabase were developed using lidar-derived elevation data and satellite imagery, and supplemented with data from targeted fieldwork, which included field verification of landslides and a detailed field survey and series of laboratory soil tests on the large, informally named Tanana 440 landslide. We identified 1,679 landslides within the FNSB region, with 681 mapped within the focused EDMAP study area. These landslides occurred in bedrock and surficial loess deposits and vary widely in age, morphology, and material type. Most are prehistoric, but we did observe some historic and active landslides. Potential landslide triggers may include thawing permafrost, rain events, seismic events, and river erosion. Our goals with this work are to increase awareness of landslides as a potential geohazard and to aid state and local agencies and the general public in making informed land management decisions. [ABSTRACT FROM AUTHOR]

The article cites the accomplishments of the Alaska Division of Geological & Geophysical Surveys (DGGS) in 2011. The division has partnered with the Division of Oil & Gas and the U.S. Geologic Survey (USGS) to evaluate the oil and gas resource potential of the Umiat-Gubic area and the Brooks Range foothills. Also outlined are the accomplishments of the DGGS in the fields of mineral resources, engineering, geology and hazards, and volcanology.

Alaska communities located along coastlines and tidally influenced rivers are vulnerable to coastal erosion. These communities face decisions that require advance planning, such as implementing shore protection or moving infrastructure. To aid in erosion planning, we estimate erosion exposure for 48 communities from the Bering to the Beaufort seas. We conduct a shoreline change assessment, forecast 60 years of erosion, and estimate the replacement cost of infrastructure in the forecast area. Of 48 communities analyzed, 33 have infrastructure within the erosion forecast area. Fifteen communities comprise 90 percent of the total replacement cost. Eleven of these, and 80 percent of total estimated cost, are in the Yukon-Kuskokwim Delta. More than 40 percent of the estimated cost is forecast to occur by the late 2030s. A summary of findings and map(s) of erosion forecast areas are provided for each community where an assessment could be performed. Erosion forecasts require a clearly identifiable shoreline that can be tracked through time in aerial imagery, as well as no major coastal protection structures in the forecast area. Erosion forecasts are not suitable for 12 communities, so we provide recommendations to address erosion concerns in those community assessment reports. The assessment conducted here is a tool for developing local hazard mitigation plans and strategies to address erosion. There are methodological limitations to linear shoreline change measurements, forecasts, and infrastructure replacement costs. Total costs are not reported in this summary due to these limitations. Users must incorporate expertise and local knowledge when interpreting results. [ABSTRACT FROM AUTHOR]

The mission of the Alaska Division of Geological & Geophysical Surveys (DGGS) is to determine the potential of Alaskan land for production of metals, minerals, fuels, and geothermal resources, the locations and supplies of groundwater and construction materials, and the potential geologic hazards to buildings, roads, bridges, and other installations and structures. To help fulfill this mission, DGGS geologists and scientists distribute public information through the creation of a wide variety of maps, digital data, and written reports. Maps play a crucial role in supporting DGGS' mission by helping geologists and scientists understand, interpret, and visualize Alaska's diverse geologic resources. Unfortunately, the overall look and feel of DGGS produced small-format maps are often inconsistent, particularly how map marginalia are included or excluded, placed, and designed. Such inconsistencies have the potential to create confusion for the user, leading to difficulties in orienting the map, measuring distances, identifying map symbols, or learning about the topic and important production information about the map. In addition, the overall appearance of some of the marginalia elements used on past DGGS maps do not conform to what is considered good cartographic design. The variation in map marginalia elements also contributes to the lack of cartographic consistency and continuity in the look and feel of the division's maps. The purpose of this Report of Investigation is to establish recommended designs for map marginalia and present guidelines for their inclusion, design, and placement. An extensive literature review was performed to compile and document accepted cartographic conventions for marginalia inclusion, design, and placement. A qualitative survey was developed and administered to gather user reactions to, and opinions about, DGGS marginalia elements. Results of the literature review and qualitative survey supported the establishment of recommended designs for map marginalia and guidelines for their inclusion and placement with the purpose of greatly increasing the consistency of DGGS smallformat maps and helping map makers critically think about the purpose, role, and considerations of each element on a map. These guidelines will offer DGGS map makers the flexibility to more easily and consistently create a variety of small-format maps that are recognizable as well-designed, professional, organizational products that have a consistent appearance, while supporting the DGGS' mission and meeting the needs of the map's intended users. [ABSTRACT FROM AUTHOR]

The Tok River area (Tanacross A-5 and A-6 quadrangles) of the eastern Alaska Range hosts a variety of ages and styles of mineralization, including stratabound basemetal sulfide, intrusion-related gold-copper-silver, and structurally controlled gold. Stratabound base-metal (Zn-Pb-Cu-Ag-Au) sulfide prospects occur in the Tanacross A-6 Quadrangle, where they are known in part as the Eagle trend. Mineralization is hosted by thin marble beds within a metamorphic package dominated by siliciclastic and rare volcanic protoliths. Sulfide minerals include sphalerite, galena, chalcopyrite, pyrrhotite, and pyrite; associated minerals include calcite, ankerite, siderite, albite, phengite, chlorite, ferro-actinolite, stilpnomelane, Fe-clinopyroxene, Ca-Mn garnet, ilvaite, and barite. Mineral assemblages, compositions, and textures indicate that base-metal sulfide mineralization experienced Permian through Jurassic regional metamorphism, and Pb-isotopic ratios are closely similar to those of Devonian to Mississippian syngenetic deposits of Interior Alaska. We interpret the Eagle trend to be a continuation of the PP-LZ trend of the Delta mineral belt, and that the Tok River area prospects are most similar to sedimentary-exhalative (SEDEX)-type systems. The Hona prospect comprises Au-Cu-Ag mineralization developed in association with a multiphase hypabyssal granodiorite stock of Late Cretaceous (ca. 75 Ma) age. Mineralization occurs with disseminated pyrrhotite, chalcopyrite, trace molybdenite, and secondary biotite within the intrusion, and with disseminated and veinlet-hosted pyrite and chalcopyrite in adjacent metamorphic rocks. Silicification, sodic, and argillic alteration occur locally, but well-developed sericitic alteration is lacking. The prospect is similar in age to the nearby Peak gold skarn and is associated with intrusions of similar composition. The geochemical signature of Hona mineralization (Au-Cu-Ag-As-Bi-Te) is similar to that of the Peak skarn and distinct from the coeval Taurus Cu-Mo-Au porphyry system. Structurally controlled gold prospects of the White Gold trend appear to have formed well after mid-Cretaceous metamorphic cooling. Mafic and felsic dikes of likely Paleogene age occur locally with structurally controlled gold mineralization and are both pre-/syn- and post-mineralization in timing. Advanced argillic alteration affects Au-As-mineralized dikes as well as mineralized country rock; such alteration reflects highly acidic hydrothermal fluids and is inconsistent with an orogenic gold deposit model. If the White Gold prospects were emplaced during the Paleocene, they are similar in age and style to the Hajdukovich property near Delta Junction and may be genetically linked to ca. 55 Ma extensional tectonics and magmatism. [ABSTRACT FROM AUTHOR]

Field investigations in the Parks Highway, Minto Flats, and Dalton Highway infrastructure corridors were conducted by the Alaska Division of Geological & Geophysical Surveys (DGGS) to support engineering-geologic decisions related to the planning, routing, and construction of future infrastructure development. Airphoto and lidar hillshade interpretations, helicopter surveys, and ground reconnaissance surveys were conducted in the ~700-mi-long by ~1-mi-wide corridor between Cook Inlet and Prudhoe Bay to develop information about landscape geomorphology and evaluate potential geologic hazards. The corridor crosses diverse terrain, several major mountain ranges, and 12 physiographic provinces. We identified a wide variety of geologic hazards along the corridor that are a product of local geomorphic conditions. This report documents our Quaternary geologic observations from the 2011, 2012, and 2013 field seasons and includes maps identifying specific geologic hazards in the infrastructure corridor. The methodology employed during this investigation, specifically concerning the evaluation of a long, relatively narrow swath across variable terrain, can be applied to other infrastructure corridor studies in Alaska and elsewhere. [ABSTRACT FROM AUTHOR]