This data lists the historically active volcanoes of Alaska and the year of the last major eruptive event. The volcanoes listed meet at least one of the following criteria since 1700 CE: 1) Documented, unquestioned eruption OR 2) A strongly suspected eruption, often an eruption documented in a historical account with very little information. Current geologic knowledge must not contradict the eruption account, OR 3) Persistent (usually on the order of decades, but certainly longer than several months) fumaroles, with temperatures (where measured) within approximately 10 degrees C of the boiling point, OR 4) Significant, measured, volcanic-related, non-eruptive deformation, OR 5) Documented earthquake swarm with strongly suspected volcanic cause. All files can be downloaded free of charge from the DGGS website http://doi.org/10.14509/30851.

The geologic map database in this data release is a reproduction of the U.S. Geological Survey Professional Paper 1762: Volcanic Processes and Geology of Augustine Volcano, Alaska, Waitt and Begét (2009). The database consists of a geologic map and one structural cross section that conform to the National Geologic Map Schema (GeMS). These data supersede USGS Data Series 677: Database for Volcanic Processes and Geology of Augustine Volcano, Alaska, McIntire and others, 2012. Augustine Island (volcano) in lower Cook Inlet, Alaska, has erupted repeatedly in late-Holocene and historical times. Eruptions typically beget high-energy volcanic processes. Most notable are bouldery debris avalanches containing immense angular clasts shed from summit domes. Coarse deposits of these avalanches form much of Augustine's lower flanks. This geologic map, at 1:25,000, show the distribution and relations of volcanic units at Augustine Volcano. This database does not reproduce all elements of the original publication. Omissions include the chart and figures showing the measured sections on Augustine Island and Shuyak Island, Alaska, and the chart and diagram for the correlation of map units. Versions of these data are provided in open-access formats that are compatible with a broad range of geospatial applications. The open-access data is derived from the file geodatabase using a python script downloadable at https://github.com/doi-usgs/gems-tools-pro. Vector data are provided as shapefiles and tabular data are provided in *.txt and *.csv formats. Any shapefiles derived from the geodatabase may have prefixes of GM_[filename] and CS_[filename] indicating features are part of the geologic map or a structural cross section, respectively. Attribute table field names may be automatically abbreviated or shortened to 10 characters to conform with the shapefile format. The annotation feature class (a native format of the Esri file geodatabase) for the structural cross section is omitted because there is no equivalent open file type. Symbology layer files (*.lyrx) are provided for symbolizing the map using the intended symbols, lines, fills and patterns and a copy of the database. We recommend Esri software users set the display reference scale between 1:10,000 and 1:24,000 for optimal display of symbology, and enable the Maplex labeling engine for optimal display of labels. Users of this database are highly encouraged to cross reference this database with the original publication.

Kasatochi is a small, isolated island volcano in the center of the Aleutian Island chain. It consists of a roughly circular cone approximately 3 km in diameter with a lake-filled central crater that is 1.2 km in diameter and extends from the highest point on the island to sea level. The oldest unit recognized is a thick series of mid-Pleistocene glaciovolcanic deposits consisting of autobrecciated lava, lahars, and volumetrically minor lava masses that we believe to have been emplaced underneath a regional ice cap. This unit is unconformably overlain by several massive Holocene lavas, above which lies a thick sequence of latest-Holocene pyroclastic deposits likely deposited during the crater-forming eruption. The 2008 eruption enlarged the preexisting crater, and produced pyroclastic density currents, surges, and fall that blanketed the entire island except for the crater wall and steep, seaward-facing cliffs on the flanks. 2008 deposits initially extended the shoreline seaward by up to 500 m. A multidisciplinary effort to document recovery of the ecosystem was initiated, and this study of the geology of the island was undertaken as part of that effort. This collection of electronic data is a supplement to the Geology of Kasatochi volcano, Aleutian Islands report and geologic map. It provides spreadsheets of sample metadata and major and trace element XRF and ICP/MS data which are included in the appendices; electron microprobe mineral analyses which are discussed in the report, but not tabulated elsewhere; and high resolution versions of panoramic photographs (appendix 1) and photomicrographs (appendix 7).

A database of the geologic map of the Katmai Volcanic Cluster as described in the original abstract: This digital publication contains all the geologic map information used to publish U.S. Geological Survey Geologic Investigations Map Series I-2778 (Hildreth and Fierstein, 2003). This is a geologic map of the Katmai volcanic cluster on the Alaska Peninsula (including Mount Katmai, Trident Volcano, Mount Mageik, Mount Martin, Mount Griggs, Snowy Mountain, Alagogshak volcano, and Novarupta volcano), and shows the distribution of ejecta from the great eruption of June, 1912 at Novarupta. Widely scattered erosional remnants of volcanic rocks, unrelated to but in the vicinity of the Katmai cluster, are also mapped. Distribution of glacial deposits, large landslides, debris avalanches, and surficial deposits are a snapshot of an ever-changing landscape.

A database of the geologic map of the Katmai Volcanic Cluster as described in the original abstract: This digital publication contains all the geologic map information used to publish U.S. Geological Survey Geologic Investigations Map Series I-2778 (Hildreth and Fierstein, 2003). This is a geologic map of the Katmai volcanic cluster on the Alaska Peninsula (including Mount Katmai, Trident Volcano, Mount Mageik, Mount Martin, Mount Griggs, Snowy Mountain, Alagogshak volcano, and Novarupta volcano), and shows the distribution of ejecta from the great eruption of June, 1912 at Novarupta. Widely scattered erosional remnants of volcanic rocks, unrelated to but in the vicinity of the Katmai cluster, are also mapped. Distribution of glacial deposits, large landslides, debris avalanches, and surficial deposits are a snapshot of an ever-changing landscape.

Radiocarbon dates, stratigraphic sections, and sample location data for samples collected at Pavlof Volcano and vicinity, Alaska, Raw Data File 2025-26, presents the results of radiocarbon dating and stratigraphic studies of volcanic ash deposits in the area around Pavlof Volcano, Alaska. We collected samples for radiocarbon dating during 10-day-long field excursions to the area in 2017-2022. In addition to collecting soil-organic matter samples for dating, we recorded stratigraphic profiles in field notebooks and documented them with digital photographs. The goal of this work is to establish the stratigraphic framework of tephra-fall deposits from Pavlof Volcano to aid in documenting the Holocene eruptive history of the volcano as recorded by the tephra deposits. These data consist of a .csv file, annotated photographs, and line drawings of stratigraphic profiles. These data are provided as a Raw Data File under an open end-user license and are available on the DGGS website: http://doi.org/10.14509/31733.

On 16 July 2021, measurements were made of the volcanic gases emitted from Iliamna Volcano, Mount Douglas, Mount Martin, and Mount Mageik (Alaska, USA) from aboard a fixed-wing aircraft. Two zenith-facing differential optical absorption spectrometers were used to measure incident scattered solar ultraviolet radiation while traversing beneath the gas plumes on multiple occasions. These data were used to derive volcanic SO2 column densities and emission rates. In addition to the remote sensing payload, two in situ instruments were used to make measurements of trace gas concentrations while on flight paths through the volcanic plumes: a USGS multi-GAS (multiple Gas Analyzer System; Werner et al., 2017) analyzer for H2O-CO2-SO2-H2S, and an Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) instrument manufactured by Los Gatos Research, Inc., for H2O-HCl-HF. The CO2, SO2, and H2S sensors were calibrated five times in-flight at ambient pressures from 804-686 hPa (~1800-3000 m altitude) using standard gases stored in 25-liter capacity tedlar bags (CO2 = 448 ppm, SO2 = 2.1 ppm, H2S, = 2.0 ppm; all gases certified at ±2% accuracy). The H2O/CO2 analyzer’s baseline response was checked using small soda lime and anhydrite cartridges to remove H2O and CO2 from ambient air, and the sulfur sensors’ baselines were derived from their responses while sampling clean ambient air. In situ gas compositions were recorded at 1-second time resolution, while radiance spectra were acquired with variable integration times depending on illumination conditions and ranging from 1 to 3 seconds. Each spectrum and gas measurement was stamped with the GPS time and location. Each spectrum was saved in a separate ASCII file which includes 1024 radiances measured in the 265 - 403 nm spectral region and metadata associated with each acquisition. The in situ measurements are saved in a spreadsheet in the *.csv format.

On 16 July 2021, measurements were made of the volcanic gases emitted from Iliamna Volcano, Mount Douglas, Mount Martin, and Mount Mageik (Alaska, USA) from aboard a fixed-wing aircraft. Two zenith-facing differential optical absorption spectrometers were used to measure incident scattered solar ultraviolet radiation while traversing beneath the gas plumes on multiple occasions. These data were used to derive volcanic SO2 column densities and emission rates. In addition to the remote sensing payload, two in situ instruments were used to make measurements of trace gas concentrations while on flight paths through the volcanic plumes: a USGS multi-GAS (multiple Gas Analyzer System; Werner et al., 2017) analyzer for H2O-CO2-SO2-H2S, and an Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) instrument manufactured by Los Gatos Research, Inc., for H2O-HCl-HF. The CO2, SO2, and H2S sensors were calibrated five times in-flight at ambient pressures from 804-686 hPa (~1800-3000 m altitude) using standard gases stored in 25-liter capacity tedlar bags (CO2 = 448 ppm, SO2 = 2.1 ppm, H2S, = 2.0 ppm; all gases certified at ±2% accuracy). The H2O/CO2 analyzer’s baseline response was checked using small soda lime and anhydrite cartridges to remove H2O and CO2 from ambient air, and the sulfur sensors’ baselines were derived from their responses while sampling clean ambient air. In situ gas compositions were recorded at 1-second time resolution, while radiance spectra were acquired with variable integration times depending on illumination conditions and ranging from 1 to 3 seconds. Each spectrum and gas measurement was stamped with the GPS time and location. Each spectrum was saved in a separate ASCII file which includes 1024 radiances measured in the 265 - 403 nm spectral region and metadata associated with each acquisition. The in situ measurements are saved in a spreadsheet in the *.csv format.

This release presents data collected during airborne volcanic gas monitoring flights at Iliamna Volcano, Alaska, that were completed between 2004-2017. Instrumented fixed-wing aircraft were used to collect in situ trace gas measurements of volcanic carbon dioxide (CO2), sulfur dioxide (SO2), and hydrogen sulfide (H2S). The sensor payload also included an upward-looking correlation spectrometer (COSPEC) and/or differential optical absorption spectroscopy (DOAS) system. The remote sensing instruments were used to derive volcanic SO2 emission rates by measuring incident scattered solar ultraviolet radiation while traversing beneath the plume. Gas compositions and COSPEC output (volts) were recorded at 1 Hz and DOAS radiance spectra were collected at approximately 1 Hz depending on the ambient light conditions. All data were stamped with the GPS time and location. Trace gas and COSPEC measurements collected on 16 flights from 2004-2017 are included in a compressed file (GasData_2004_2017_v2.zip) that contains spreadsheets saved in the *.csv format and named using the local date on which the flight occurred in YYYYMMDD format (YYYY = year, MM = month, DD = day). The known values of COSPEC calibration cells used to scale raw measurements and information about gas standards used during in-flight CO2, SO2, and H2S sensor verifications are given in an auxiliary file (GasStandards.csv). DOAS data were collected during 3 flights from 2015-2017; each DOAS spectrum was saved in a separate ASCII file which includes 2048 radiances measured in the 285 - 430 nm spectral region and metadata associated with each acquisition. Additional information concerning the instruments and methods used to collect data from 2004-2007 is available in Doukas and McGee (2007), and in Kelly et al. (2013) and Werner et al. (2013) for data collected after 2007. See the associated publication for analysis and discussion of these data: Werner, C., Power, J., Kelly, P., Prejean, S., & Kern, C., 2021, Characterizing unrest: A retrospective look at 20 years of gas emissions and seismicity at Iliamna Volcano, Alaska. Journal of Volcanology and Geothermal Research, 107448. https://doi.org/https://doi.org/10.1016/j.jvolgeores.2021.107448 References Doukas, M. P., & McGee, K. A., 2007, A compilation of gas emission-rate data from volcanoes of Cook Inlet (Spurr, Crater Peak, Redoubt, Iliamna, and Augustine) and Alaska Peninsula (Douglas, Fourpeaked, Griggs, Mageik, Martin, Peulik, Ukinrek Maars, and Veniaminof), Alaska, from 1995-2006. https://pubs.usgs.gov/of/2007/1400/of2007-1400.pdf Kelly, P. J., Kern, C., Roberts, T. J., Lopez, T., Werner, C., & Aiuppa, A., 2013, Rapid chemical evolution of tropospheric volcanic emissions from Redoubt Volcano, Alaska, based on observations of ozone and halogen-containing gases. Journal of Volcanology and Geothermal Research, 259, 317–333. https://doi.org/10.1016/J.JVOLGEORES.2012.04.023 Werner, C., Kelly, P. J., Doukas, M., Lopez, T., Pfeffer, M., McGimsey, R., & Neal, C., 2013, Degassing of CO2, SO2, and H2S associated with the 2009 eruption of Redoubt Volcano, Alaska. Journal of Volcanology and Geothermal Research, 259. https://doi.org/10.1016/j.jvolgeores.2012.04.012