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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 181 records · Page 10Linked to original sources
USGS1998

MAS/MILS Arc/Info point coverage for the western U.S. (excluding Hawaii)

The U.S. Geological Survey has two international and one regional digital database that contains information on mineral properties. This report describes the conversion of selected data from one of the international databases - MAS/MILS (Mineral Availability System/Mineral Industry Location System) - into a spatial data product. The MAS/MILS database, obtained from the U.S. Bureau of Mines (USBM) upon its closure, contains over 221,000 records of mineral properties and processing facilities throughout the world. However, the majority of the records in the database are of sites located in the western U.S. This is due to the extensive mineral activity that has occurred in the West, and the work done by mineral professionals in the Western, Alaska, and Intermountain Field Operations Centers of the USBM. The purpose of this project was to create a spatial coverage of the western U.S. containing mineral resource information. This coverage includes information for the states of Alaska, Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. For this report, locations from MAS/MILS were converted to a point coverage using a geographic information system (GIS). All work was done using Arc/Info v. 7.0.4. There are 128,441 points in the coverage.

Alaska, Arizona, California, Colorado, Idaho, Mont↗
USGS2009

U.S. Geological Survey (USGS) Western Region: Coastal and Ocean Science

USGS Western Region Coastal and Ocean Science is interdisciplinary, collaborative, and integrates expertise from all USGS Disciplines, and ten of its major Science Centers, in Alaska, Hawai'i, California, Washington, and Oregon. The scientific talent, laboratories, and research vessels in the Western Region and across the Nation, strategically position the USGS to address broad geographic and oceanographic research topics. USGS information products inform resource managers and policy makers who must balance conservation mandates with increasing demands for resources that sustain the Nation's economy. This fact sheet describes but a few examples of the breadth of USGS science conducted in coastal, nearshore, and ocean environments along our Nation's West Coast and Pacific Islands.

Fact Sheet↗
USGS2025

Estimated average annualized losses from potential building damage and fatalities due to earthquake-generated tsunamis in the United States

Earthquake-generated tsunamis represent substantial economic threats to states and territories in the United States (U.S.), but we are unaware of any effort to quantify potential impacts at the national level. This gap is partially due to the lack of nationally consistent data on tsunamigenic sources and associated return periods. This study addresses this issue and provides estimates of average annualized losses (AAL) for potential residential fatalities and capital stock losses associated with building damage (i.e., structural, non-structural, contents, and inventory damage) in the U.S. by curating tsunami-hazard information based on deterministic scenarios and probabilistic approaches, calculating potential losses, and estimating return periods where necessary. This assessment was done for the U.S. West Coast, Alaska, Hawaii, U.S. Pacific Territories, and U.S. Atlantic Territories. We estimate that earthquake-generated tsunamis that could affect these states and territories collectively represent $1 billion in potential AAL with 79 % of losses due to residential fatalities and 21 % of losses due to capital stock losses from building damage. We identify AAL variations based on county and county equivalents, states and territories, geographic regions, return periods, and departure-delay assumptions for evacuating residents. Results include high AAL values for potential fatalities in Puerto Rico and the U.S. Pacific Northwest region, high AAL values for potential building-related damage in Hawaii and California, and high building- and population-loss ratios for county equivalents in Alaska and U.S. territories.

International Journal of Disaster Risk Reduction↗
USGS2016

Helminth community structure in two species of arctic-breeding waterfowl

Climate change is occurring rapidly at high latitudes, and subsequent changes in parasite communities may have implications for hosts including wildlife and humans. Waterfowl, in particular, harbor numerous parasites and may facilitate parasite movement across broad geographic areas due to migratory movements. However, little is known about helminth community structure of waterfowl at northern latitudes. We investigated the helminth communities of two avian herbivores that breed at high latitudes, Pacific black brant ( Branta bernicla nigricans ), and greater white-fronted geese ( Anser albifrons ), to examine effects of species, geographic area, age, and sex on helminth species richness, aggregation, prevalence, and intensity. We collected 83 and 58 black brant and white-fronted geese, respectively, from Arctic and Subarctic Alaska July-August 2014. We identified 10 known helminth species ( Amidostomum anseris , Amidostomum spatulatum , Drepanidotaenia lanceolata , Epomidiostomum crami , Heterakis dispar , Notocotylus attenuatus , Tetrameres striata , Trichostrongylus tenuis , Tschertkovilepis setigera , and Wardoides nyrocae ) and 1 previously undescribed trematode. All geese sampled were infected with at least one helminth species. All helminth species identified were present in both age classes and species, providing evidence of transmission at high latitudes and suggesting broad host susceptibility. Also, all but one helminth species were present at both sites, suggesting conditions are suitable for transmission across a large latitudinal/environmental gradient. Our study provides important baseline information on avian parasites that can be used to evaluate the effects of a changing climate on host-parasite distributions.

Alaska↗
USGS2019

Artificial intelligence and avian influenza: Using machine learning to enhance active surveillance for avian influenza viruses

Influenza A viruses are one of the most significant viral groups globally with substantial impacts on human, domestic animal and wildlife health. Wild birds are the natural reservoirs for these viruses, and active surveillance within wild bird populations provides critical information about viral evolution forming the basis of risk assessments and countermeasure development. Unfortunately, active surveillance programs are often resource‐intensive, and thus, enhancing programs for increased efficiency is paramount. Machine learning, a branch of artificial intelligence applications, provides statistical learning procedures that can be used to gain novel insights into disease surveillance systems. We use a form of machine learning, gradient boosted trees, to estimate the probability of isolating avian influenza viruses (AIV) from wild bird samples collected during surveillance for AIVs from 2006 to 2011 in the United States. We examined several predictive features including age, sex, bird type, geographic location and matrix gene rRT‐PCR results. Our final model had high predictive power and only included geographic location and rRT‐PCR results as important predictors. The highest predicted viral isolation probability was for samples collected from the north‐central states and the south‐eastern region of Alaska. Lower rRT‐PCR Ct‐values are associated with increased likelihood of AIV isolation, and the model estimated 16% probability of isolating AIV from samples declared negative (i.e., ≥35 Ct‐value) using the rRT‐PCR screening test and standard protocols. Our model can be used to prioritize previously collected samples for isolation and rapidly evaluate AIV surveillance designs to maximize the probability of viral isolation given limited resources and laboratory capacity.

Transboundary and Emerging Diseases↗
USGS1998

Geographic trend in mercury measured in common loon feathers and blood

The common loon ( Gavia immer ) is a high‐trophic‐level, long‐lived, obligate piscivore at risk from elevated levels of Hg through biomagnification and bioaccumulation. From 1991 to 1996 feather ( n = 455) and blood ( n = 381) samples from adult loons were collected between June and September in five regions of North America: Alaska, northwestern United States, Upper Great Lakes, New England, and the Canadian Maritimes. Concentrations of Hg in adults ranged from 2.8 to 36.7 μg/g (fresh weight) in feathers and from 0.12 to 7.80 μg/g (wet weight) in whole blood. Blood Hg concentrations in 3 to 6‐week‐old juveniles ranged from 0.03 to 0.78 μg/g (wet weight) ( n = 183). To better interpret exposure data, relationships between blood and feather Hg concentrations were examined among age and sex classes. Blood and feather Hg concentrations from the same individuals were significantly correlated and varied geographically ( r 2 ranged from 0.03 to 0.48). Blood and feather Hg correlated strongest in areas with the highest blood Hg levels, indicating a possible carryover of breeding season Hg that is depurated during winter remigial molt. Mean blood and feather Hg concentrations in males were significantly higher than concentrations in females for each region. The mean blood Hg concentration in adults was 10 times higher than that in juveniles, and feather Hg concentrations significantly increased over 1 to 4‐year periods in recaptured individuals. Geographic stratification indicates a significant increasing regional trend in adult and juvenile blood Hg concentrations from west to east. This gradient resembles U.S. Environmental Protection Agency‐modeled predictions of total anthropogenic Hg deposition across the United States. This gradient is clearest across regions. Within‐region blood Hg concentrations in adults and juveniles across nine sites of one region, the Upper Great Lakes, were less influenced by variations in geographic Hg deposition than by hydrology and lake chemistry. Loons breeding on low‐pH lakes in the Upper Great Lakes and in all lake types of northeastern North America are most at risk from Hg.

Alaska, Maine, Michigan, Minnesota, Montana, New B↗
USGS2021

Identification of seasonal streamflow regimes and streamflow drivers for daily and peak flows in Alaska

Alaska is among northern high‐latitude regions where accelerated climate change is expected to impact streamflow properties, including seasonality and primary flow drivers. Evaluating changes to streamflow, including flood characteristics, across this large and diverse environment can be improved by identifying the distribution and influence of flow drivers. Using metrics of mean monthly streamflow data from 253 streamgages, seasonal flow regimes were clustered to guide identification of seasonal‐flow drivers and form hydrologic groups for identification of peak‐flow populations. Nine seasonally distinct subclasses described variability within three classes dominated by (mostly fall) rainfall, (spring) snowmelt, and (summer) high‐elevation melt. The most glacierized basins exclusively grouped into high‐elevation melt subclasses, and less glacierized basins sometimes exhibited seasonal patterns aligned with rainfall‐ and snowmelt‐dominated regimes. Peak‐flow populations varied by subclass from dominant rainfall or dominant snowmelt to mixed rainfall‐snowmelt or mixed rainfall, snowmelt, and high‐elevation melt. Within subclasses, rainfall generated higher mean peak flows (relative to mean annual flow) than snowmelt or high‐elevation melt. Seasonal flow regimes showed clear but complex associations with basin characteristics, primarily elevation and winter temperature, and with geographic location. These dependencies provided elevation‐based analogies for changes associated with warming and insights for seasonal flow regime prediction and hydrologic region delineation. These results provide a spatially comprehensive perspective on seasonal streamflow drivers across Alaska from historical data and serve as an important historical basis for analysis.

Alaska↗
USGS1962

Mercury in the United States, exclusive of Alaska and Hawaii

This map shows the location of mercury districts and deposits in the United States (exclusive of Alaska and Hawaii). The map was compiled from published reports and from data in the files of the Geological Survey. All map locations are numbered consecutively in each state and names, geographic coordinates, and selected references are given in the Index.

Mineral Investigations Resource Map↗
USGS2014

Landscape and climate science and scenarios for Florida

The Peninsular Florida Landscape Conservation Cooperative (PFLCC) is part of a network of 22 Landscape Conservation Cooperatives (LCCs) that extend from Alaska to the Caribbean. LCCs are regional-applied conservation-science partnerships among Federal agencies, regional organizations, States, tribes, nongovernmental organizations (NGOs), private stakeholders, universities, and other entities within a geographic area. The goal of these conservation-science partnerships is to help inform managers and decision makers at a landscape scale to further the principles of adaptive management and strategic habitat conservation. A major focus for LCCs is to help conservation managers and decision makers respond to large-scale ecosystem and habitat stressors, such as climate change, habitat fragmentation, invasive species, and water scarcity. The purpose of the PFLCC is to facilitate planning, design, and implementation of conservation strategies for fish and wildlife species at the landscape level using the adaptive management framework of strategic habitat conservation—integrating planning, design, delivery, and evaluation. Florida faces a set of unique challenges when responding to regional and global stressors because of its unique ecosystems and assemblages of species, its geographic location at the crossroads of temperate and tropical climates, and its exposure to both rapid urbanization and rising sea levels as the climate warms. In response to these challenges, several landscape-scale science projects were initiated with the goal of informing decision makers about how potential changes in climate and the built environment could impact habitats and ecosystems of concern in Florida and the Southeast United States. In June 2012, the PFLCC, North Carolina State University, convened a workshop at the U.S. Geological Survey (USGS) Coastal and Marine Science Center in St. Petersburg to assess the results of these integrated assessments and to foster an open dialogue about science gaps and future research needs.

Florida↗
USGS2003

Two distinct phylogenetic clades of infectious hematopoietic necrosis virus overlap within the Columbia River basin

Infectious hematopoietic necrosis virus (IHNV), an aquatic rhabdovirus, causes a highly lethal disease of salmonid fish in North America. To evaluate the genetic diversity of IHNV from throughout the Columbia River basin, excluding the Hagerman Valley, Idaho, the sequences of a 303 nt region of the glycoprotein gene (mid-G) of 120 virus isolates were determined. Sequence comparisons revealed 30 different sequence types, with a maximum nucleotide diversity of 7.3% (22 mismatches) and an intrapopulational nucleotide diversity of 0.018. This indicates that the genetic diversity of IHNV within the Columbia River basin is 3-fold higher than in Alaska, but 2-fold lower than in the Hagerman Valley, Idaho. Phylogenetic analyses separated the Columbia River basin IHNV isolates into 2 major clades, designated U and M. The 2 clades geographically overlapped within the lower Columbia River basin and in the lower Snake River and tributaries, while the upper Columbia River basin had only U clade and the upper Snake River basin had only M clade virus types. These results suggest that there are co-circulating lineages of IHNV present within specific areas of the Columbia River basin. The epidemiological significance of these findings provided insight into viral traffic patterns exhibited by IHNV in the Columbia River basin, with specific relevance to how the Columbia River basin IHNV types were related to those in the Hagerman Valley. These analyses indicate that there have likely been 2 historical events in which Hagerman Valley IHNV types were introduced and became established in the lower Columbia River basin. However, the data also clearly indicates that the Hagerman Valley is not a continuous source of waterborne virus infecting salmonid stocks downstream.

Diseases of Aquatic Organisms↗
USGS2016

Detecting significant change in stream benthic macroinvertebrate communities in wilderness areas

A major challenge in the biological monitoring of stream ecosystems in protected wilderness areas is discerning whether temporal changes in community structure are significantly outside of a reference condition that represents natural or acceptable annual variation in population cycles. Otherwise sites could erroneously be classified as impaired. Long-term datasets are essential for understanding these trends, to ascertain whether any changes in community structure significantly beyond the reference condition are permanent shifts or with time move back to within previous limits. To this end, we searched for long-term (>8 years) quantitative data sets of macroinvertebrate communities in wadeable rivers collected by similar methods and time of year in protected wilderness areas with minimal anthropogenic disturbance. Four geographic areas with datasets that met these criteria in the USA were identified, namely: McLaughlin Nature Reserve in California (1 stream), Great Smoky Mountains National Park in Tennesse-North Carolina (14 streams), Wind River Wilderness Areas in Wyoming (3 streams) and Denali National Park and Preserve in Alaska (6 streams). Two statistical approaches were applied: Taxonomic Distinctness (TD) to describe changes in diversity over time and non-metric multidimensional scaling (MDS) to describe changes over time in community persistence (Jaccards Index) and community stability (Bray–Curtis Index). Control charts were used to determine if years in MDS plots were significantly outside a reference condition. For Hunting Creek, TD showed three years outside natural variation which could be attributed to severe hydrological events but years outside the natural-variation funnel at sites in other geographical areas were inconsistent and could not be explained by environmental variables. TD identified simulated severe pollutant events which caused the removal of entire invertebrate assemblages but not simulated water temperature shifts. Within a region, both MDS analyses typically identified similar years as exceeding reference condition variation, illustrating the utility of the approach for identifying wider spatial scale effects that influence more than one stream. MDS responded to both simulated water temperature stress and a pollutant event, and generally outlying years on MDS plots could be explained by environmental variables, particularly higher precipitation. Multivariate control charts successfully identified whether shifts in community structure identified by MDS were significant and whether the shift represented a press disturbance (long-term change) or a pulse disturbance. We consider a combination of TD and MDS with control charts to be a potentially powerful tool for determining years significantly outside of a reference condition variation.

Alaska, California, North Carolina, Tennesse, Wyom↗
USGS2019

Phenology of hatching, emergence, and end-of-season body size in young-of-year Coho Salmon in thermally contrasting streams draining the Copper River Delta, Alaska

Phenology can be linked to individual fitness, particularly in strongly seasonal environments where the timing of events have important consequences for growth, condition, and survival. We studied the phenology of Coho Salmon hatching and emergence in streams with contrasting thermal variability, but in close geographic proximity. Following emergence, we tracked body sizes of cohorts of young-of-year fish until the end of the growing season. Hatch and emergence timing occurred at the same time among streams with marked variability in thermal regimes. We demonstrate that this can be explained in part by the thermal units accumulated during embryo development. At the end of the first growing season there were some differences in body size, however overall fish size among streams were similar despite strong differences in thermal regimes. Collectively these results provide novel insights into the interactions between environmental variability and the early life-history stages of Coho Salmon furthering our understanding of the consequences of phenology on growth and survival for individuals within the critical first summer of life.

Alaska↗
USGS2015

Surveillance potential of non-native Hawaiian birds for detection of West Nile Virus

West Nile virus (WNV) was first detected in North America in 1999. Alaska and Hawaii (HI) remain the only U.S. states in which transmission of WNV has not been detected. Dead bird surveillance has played an important role in the detection of the virus geographically, as well as temporally. In North America, corvids have played a major role in WNV surveillance; however, the only corvid in HI is the endangered Hawaiian crow that exists only in captivity, thus precluding the use of this species for WNV surveillance in HI. To evaluate the suitability of alternate avian species for WNV surveillance, we experimentally challenged seven abundant non-native bird species present in HI with WNV and compared mortality, viremia, oral shedding of virus, and seroconversion. For detection of WNV in oral swabs, we compared viral culture, reverse-transcriptase polymerase chain reaction, and the RAMP ® test. For detection of antibodies to WNV, we compared an indirect and a competitive enzyme-linked immunoassay. We found four species (house sparrow, house finch, Japanese white-eye, and Java sparrow) that may be useful in dead bird surveillance for WNV; while common myna, zebra dove, and spotted dove survived infection and may be useful in serosurveillance.

American Journal of Tropical Medicine and Hygiene↗
USGS1996

Geographic variation in migratory behavior of greater white-fronted geese ( Anser albifrons )

We studied the migration and winter distribution of adult Greater White-fronted Geese ( Anser albifrons frontalis ) radio-marked on the Yukon-Kuskokwim Delta (YKD) and Bristol Bay Lowlands (BBL) of Alaska from 1987 to 1992. The major autumn staging site for geese from both breeding areas was the Klamath Basin on the California/Oregon border. However, temporal use of this area differed markedly between populations. Geese from the BBL arrived at the Klamath Basin nearly 30 days before geese from the YKD and departed before most YKD geese had arrived. Ninety percent of BBL geese used the Klamath Basin in autumn, whereas 30% of YKD geese bypassed the Klamath Basin during autumn and instead flew directly to the Central Valley of California. Nearly all BBL geese migrated directly from the Klamath Basin to wintering areas in Mexico, bypassing the Central Valley. Ninety percent of the BBL geese wintered in Mexico, as opposed to <20% of the YKD geese. Wetlands of the Interior Highlands in the state of Chihuahua, particularly Laguna Babicora, were used by >90% of the radio-marked geese in Mexico. Marshes along the West Coast comprised the other important wintering habitat in Mexico. The Sacramento Valley of California was the predominant wintering area for YKD geese. BBL geese migrated north from Mexico into the San Joaquin Valley or Sacramento-San Joaquin Delta of California by the last week of January. Fifty-five percent of the BBL population used the Klamath Basin in spring, but many birds staged in eastern Oregon and western Idaho. In contrast, geese from the YKD staged almost exclusively in the Klamath Basin during spring before flying to staging areas in Alaska. Breeding allopatry and temporal partitioning on staging and wintering areas likely has contributed to the evolution of previously described phenotypic differences between these populations. These two populations, along with the Tule Greater White-fronted Goose (A. a. gambeli), may constitute a portion of a Rassenkreis, a group of subspecies connected by clines, each ecotype of which has independent conservation needs.

The Auk↗
USGS2001

The National Petroleum Reserve-Alaska (NPRA) data archive

The area currently known as the National Petroleum ReserveAlaska was originally designated in 1923 as Naval Petroleum Reserve No. 4 (NPR4). It was one of four U.S. regions thought to contain significant amounts of oil that were to be reserved for national crises. Geographic and geologic knowledge of the NPR4 was only superficial in 1923. Earlier exploration, however, had shown that the region contained the ingredients necessary for oil accumulations to exist: source rocks, reservoir rocks, and geologic structures that could trap petroleum. Oil seeps on the coast and the size of the area (some 37,000 square miles, about the size of Indiana) reinforced the notion that significant quantities of petroleum were present.

Fact Sheet↗
USGS2005

Murre eggs ( Uria aalge and Uria lomvia ) as indicators of mercury contamination in the Alaskan marine environment

Sixty common murre ( Uria aalge ) and 27 thick-billed murre ( Uria lomvia ) eggs collected by the Seabird Tissue Archival and Monitoring Project (STAMP) in 1999−2001 from two Gulf of Alaska and three Bering Sea nesting colonies were analyzed for total mercury (Hg) using isotope dilution cold vapor inductively coupled mass spectrometry. Hg concentrations (wet mass) ranged from 0.011 μg/g to 0.357 μg/g (relative standard deviation = 76%), while conspecifics from the same colonies and years had an average relative standard deviation of 33%. Hg levels in eggs from the Gulf of Alaska (0.166 μg/g ± 0.011 μg/g) were significantly higher ( p < 0.0001) than in the Bering Sea (0.047 μg/g ± 0.004 μg/g). Within the Bering Sea, Hg was significantly higher ( p = 0.0007) in eggs from Little Diomede Island near the arctic than at the two more southern colonies. Although thick-billed and common murres are ecologically similar, there were significant species differences in egg Hg concentrations within each region ( p < 0.0001). In the Bering Sea, eggs from thick-billed murres had higher Hg concentrations than eggs from common murres, while in the Gulf of Alaska, common murre eggs had higher concentrations than those of thick-billed murres. A separate one-way analysis of variance on the only time−trend data currently available for a colony (St. Lazaria Island in the Gulf of Alaska) found significantly lower Hg concentrations in common murre eggs collected in 2001 compared to 1999 ( p = 0.017). Results from this study indicate that murre eggs may be effective monitoring units for detecting geographic, species, and temporal patterns of Hg contamination in marine food webs. The relatively small intracolony variation in egg Hg levels and the ability to consistently obtain adequate sample sizes both within and among colonies over a large geographic range means that monitoring efforts using murre eggs will have suitable statistical power for detecting environmental patterns of Hg contamination. The potential influences of trophic effects, physical transport patterns, and biogeochemical processes on these monitoring efforts are discussed, and future plans to investigate the sources of the observed variability are presented.

Environmental Science & Technology↗
USGS2006

Atlas of relations between climatic parameters and distributions of important trees and shrubs in North America - Alaska species and ecoregions

Climate is the primary factor in controlling the continental-scale distribution of plant species, although the relations between climatic parameters and species' ranges is only now beginning to be quantified. Preceding volumes of this atlas explored the continental-scale relations between climatic parameters and the distributions of woody plant species across all of the continent of North America. This volume presents similar information for important woody species, groups of species, and ecoregions in more detail for the State of Alaska. For these analyses, we constructed a 25-kilometer equal-area grid of modern climatic and bioclimatic parameters for North America from instrumental weather records. We obtained a digital representation of the geographic distribution of each species or ecoregion, either from a published source or by digitizing the published distributions ourselves. The presence or absence of each species or ecoregion was then determined for each point on the 25-kilometer grid, thus providing a basis for comparison of the climatic data with the geographic distribution of each species or ecoregion. The relations between climate and these distributions are presented in graphical and tabular form.

Alaska↗
USGS2019

Detrital zircon geochronology along a structural transect across the Kahiltna assemblage in the western Alaska Range: Implications for emplacement of the Alexander-Wrangellia-Peninsular terrane against North America

The Kahiltna assemblage in the western Alaska Range consists of deformed Upper Jurassic and Cretaceous clastic strata that lie between the Alexander-Wrangellia-Peninsular (AWP) terrane to the south, and the Farewell and other peri-cratonic terranes to the north. Differences in detrital zircon populations and sandstone petrography allow geographic separation of the strata into two different successions, each consisting of multiple units, or petrofacies, with distinct provenance and lithologic characteristics. The northwestern succession was largely derived from older, inboard peri-cratonic terranes and correlates along strike to the southwest with the Kuskokwim Group. The southeastern succession is characterized by volcanic and plutonic rock detritus derived from Late Jurassic igneous rocks of the AWP terrane and mid to Late Cretaceous arc related igneous rocks and is part of a longer belt to the southwest and northeast, here named the Koksetna-Clearwater belt. The two successions remained separate depositional systems until the Late Cretaceous, when the northwestern succession overlapped the southeastern succession at about 81 Ma and they were deformed together by about 80 Ma by southeast-verging fold-and-thrust style deformation interpreted to represent final accretion of the AWP terrane along the southern Alaska margin. We interpret the tectonic evolution of the Kahiltna successions as a progression from forearc sedimentation and accretion in a south-facing continental magmatic arc to arrival and partial underthrusting of the backarc flank of an active, south-facing island arc system (AWP terrane). A modern analogue is the ongoing collision and partial underthrusting of the Izu-Bonin-Marianas island arc beneath the Japan Trench-Nankai Trough on the east side of central Japan.

Alaska↗