Stratigraphic and electron microprobe data for Holocene tephra from Makushin Volcano, Alaska, and for interbedded tephra from other volcanoes located among or near the islands of the eastern Aleutians

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Frequently anticipated questions:


What does this data set describe?

Title:
Stratigraphic and electron microprobe data for Holocene tephra from Makushin Volcano, Alaska, and for interbedded tephra from other volcanoes located among or near the islands of the eastern Aleutians
Abstract:
Stratigraphic and electron microprobe data for Holocene tephra from Makushin Volcano, Alaska, and for interbedded tephra from other volcanoes located among or near the islands of the eastern Aleutians, Raw Data File 2026-12, summarizes tephrostratigraphy and electron probe microanalytical (EPMA) data from Makushin Volcano and regional tephras in the Unalaska Island area. The data were collected by scientists from the Alaska Volcano Observatory (AVO) and the Cascades Volcano Observatory during fieldwork from 2011 to 2024. Additional EPMA analyses from this time interval are reported in Larsen and others (2020). Makushin Volcano is part of the Makushin Volcanic Field (McConnell and others, 1998) in the north central part of Unalaska Island, Alaska, approximately 1,290 km southwest of Anchorage and 20 km west of the City of Unalaska and the Port of Dutch Harbor. Makushin erupted explosively to produce two large-volume, explosive Holocene deposits with ages of 9,040 (Makushin Valley) and 7,900 (Driftwood) cal. yr B.P. Since then, Makushin Volcano has erupted numerous times, though individual eruptions have been significantly less voluminous than those of the early Holocene events. The most recent eruption in 1995 produced small ash plumes but left no clearly preserved deposits. Eruptions from volcanoes on neighboring islands also deposited significant tephra fall on Unalaska Island. Tephra from the Okmok II caldera-forming eruption about 2050 years ago is 1-2 cm thick and drapes the area near Dutch Harbor and the City of Unalaska. Tephra from two large explosive eruptions of the Akutan volcano also covered the area 1,600 and 8,700 years ago. Tephra from the older Akutan eruption is up to 40 cm thick in the City of Unalaska. An additional, older silicic tephra sample originated from a distant volcano, but its provenance remains undetermined. Data in this report are included in the public Geologic Database of Information on Volcanoes in Alaska (GeoDIVA; Cameron and others, 2022, http://doi.org/10.14509/geodiva). These data and accompanying discussion are released as a DGGS Raw Data File, and all publication components are available from the DGGS website at: http://doi.org/10.14509/32059.
Supplemental_Information:
Makushin-Stations:    Stratigraphic section and sample station ID numbers, coordinates, and location descriptions.	
Makushin-Samples:    Sample ID numbers with station ID, source volcano, sample type, and description.	
Makushin-Layers:    Stratigraphic section layer data from each project year.	
Makushin-EPMA:    Single-point EPMA analyses including sample ID, session date, MethodID, analytical group, point number, and glass populations.	
Makushin-Analytical-Conditions:    Analytical conditions, MethodID, calibration standards, detector, crystal, and count times.	
Makushin-Standards:    Working standard data in single analytical point format.
  1. How might this data set be cited?
    Larsen, J.F., Schaefer, J.R., Dietterich, H.R., Vallance, J.W., Rosenkrans, H.S., Van Eaton, Alexa, Wallace, K.L., Kleiner, Wil, and Hatfield, Virginia, 2026, Stratigraphic and electron microprobe data for Holocene tephra from Makushin Volcano, Alaska, and for interbedded tephra from other volcanoes located among or near the islands of the eastern Aleutians: Raw Data File RDF 2026-12, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 5 p.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -167.052549
    East_Bounding_Coordinate: -165.810670
    North_Bounding_Coordinate: 54.166020
    South_Bounding_Coordinate: 53.498643
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2025
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: spreadsheet
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a point data set.
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.0000001. Longitudes are given to the nearest 0.0000001. Latitude and longitude values are specified in decimal degrees. The horizontal datum used is NAD83.
      The ellipsoid used is GRS 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222101.
  7. How does the data set describe geographic features?
    rdf2026-12-Makushin-Stations.xlsx, rdf2026-12-Makushin-Stations-Data-Dictionary.xlsx
    Stratigraphic section and sample station ID numbers, coordinates, and location descriptions. (Source: AVO)
    rdf2026-12-Makushin-Samples.xlsx, rdf2026-12-Makushin-Samples-Data-Dictionary.xlsx
    Sample ID numbers with station ID, source volcano, sample type, and description. (Source: AVO)
    rdf2026-12-Makushin-Layers.xlsx, rdf2026-12-Makushin-Layers-Data-Dictionary.xlsx
    Stratigraphic section layer data from each project year. (Source: AVO)
    rdf2026-12-Makushin-EPMA.xlsx, rdf2026-12-Makushin-EPMA-Data-Dictionary.xlsx
    Single-point EPMA analyses including sample ID, session date, MethodID, analytical group, point number, and glass populations. (Source: AVO)
    rdf2026-12-Makushin-Analytical-Conditions.xlsx, rdf2026-12-Makushin-Analytical-Conditions-Data-Dictionary.xlsx
    Analytical conditions, MethodID, calibration standards, detector, crystal, and count times. (Source: AVO)
    rdf2026-12-Makushin-EPMA-Standards.xlsx, rdf2026-12-Makushin-EPMA-Standards-Data-Dictionary.xlsx
    Working standard data in single analytical point format. (Source: AVO)

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
  2. Who also contributed to the data set?
    Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Matt Loewen provided ample assistance with the stratigraphic section data sheets. Michelle Coombs assisted with correlating Nateekin electron microprobe data with the Akutan source eruption. We thank the U.S. Fish and Wildlife Service and the Ounalashka Corporation for permission to conduct this fieldwork on their lands and for their generous assistance with many aspects of our fieldwork and engagement with the Unalaska community. Maritime Helicopters and Pathfinder Aviation supported this work, and we thank their pilots for safe and successful field seasons.
  3. To whom should users address questions about the data?
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    dggspubs@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.

Why was the data set created?

This dataset contains LA-ICP-MS U-Pb zircon ages and trace and rare-earth element data from 14 igneous and metaigneous samples collected for the USGS Earth MRI Steese and Chena mapping projects. These data support efforts to modernize geologic mapping in regions with critical mineral potential across the Yukon-Tanana Upland. The purpose of the dataset is to constrain the timing of igneous activity to inform geologic mapping, tectonic interpretations, and mineralization studies in east-central Alaska.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 2024 (process 1 of 2)
    Field data collection - AVO geologists collected samples and recorded observations from 109 stratigraphic sections during fieldwork conducted between 2011 and 2024. Stratigraphic sections were described and recorded in field notebooks during the 2011-2018 seasons. During 2023 and 2024, the sections were described both in field notebooks and digitally using the StraboSpot iPad software (strabospot.org). Location data were collected with handheld GPS devices and recorded in field notebooks. Station locations are provided using the NAD83 datum.
    Date: 2025 (process 2 of 2)
    Sample analysis - This report presents EPMA data from 126 tephra samples. The samples were collected in the field and processed at the U.S. Geological Survey Alaska Tephra Laboratory (USGS ATL) in Anchorage. Bulk samples were sonicated in tap water for 10 to 30 minutes, wet sieved into greater than 250 micrometer, 125 to 250 micrometer, and 63 to 125 micrometer fractions, and material finer than 63 micrometer was discarded. The sieved fractions were dried at 40 degrees Celsius for 12 to 24 hours and examined under a binocular microscope to identify the size fraction with the highest glass content. For most samples, the modal fraction was selected for analysis and used to prepare grain mounts. Polished grain mounts were produced on one inch epoxy pucks and glass slides at USGS ATL and the University of Alaska Fairbanks (UAF), following Loewen et al. (2023). Analyses were performed on the UAF JEOL JXA 8530F electron microprobe using the AVO tephra routine. Operating conditions were 15 kiloelectron volts, 5 to 10 nanoamperes, and a 5 micrometer beam to reduce alkali migration. Sodium was measured first, and time dependent intensity corrections were applied using Probe for EPMA software. Calibration standards included common mineral and glass reference materials; details for each analytical session are provided in a separate table. Working standards, analyzed throughout each session, included rhyolitic glass, CCNM, and basaltic glasses BG 2 and BG 3. Analytical uncertainties are discussed in Loewen et al. (2023). Additional details on laboratory methods and data reduction are provided in the accompanying report.
  3. What similar or related data should the user be aware of?
    Cameron, C.E., Crass, S.W., and Staff, AVO, 2022, Geologic Database of Information on Volcanoes in Alaska (GeoDIVA): Digital Data Series DDS 20, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Larsen, J.F., Neal, C.A., Schaefer, J.R., and Nye, C.J., 2023, Geologic map of Okmok Volcano: Report of Investigation RI 2023-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 63 p., 4 sheets
    Loewen, M.W., Wallace, K.L., Lubbers, Jordan, Ruth, Dawn, Izbekov, P.E., Larsen, J.F., and Graham, Nathan, 2023, Glass electron microprobe analyses methods, precision and accuracy for tephra studies in Alaska: Miscellaneous Publication MP 174, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 20 p
    McConnell, V.S., Beget, J.E., Roach, A.L., Bean, K.W., and Nye, C.J., 1998, Geologic map of the Makushin volcanic field, Unalaska Island, Alaska: Report of Investigation RI 97-20, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 2 sheets, scale 1:63,360

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    The accompanying report and data tables provide a comprehensive discussion of processing methods, with errors reported in the tables where applicable. This data is being released as part of the DGGS RDF series, which includes content describing approved techniques and methods for the collection, storage, visualization, analysis, and interpretation of scientific data. While the information has been reviewed by several geologists familiar with the study area, the data and report have not undergone formal review for technical content or conformity to DGGS editorial standards. For inquiries regarding analytical values or procedures, the originating lab is the best point of contact.
  2. How accurate are the geographic locations?
    Location data were collected with handheld GPS devices and recorded in field notebooks.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This data release is complete.
  5. How consistent are the relationships among the observations, including topology?
    Not applicable

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints:
This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).
Use_Constraints:
Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.
  1. Who distributes the data set? (Distributor 1 of 1)
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    dggspubs@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.
  2. What's the catalog number I need to order this data set? RDF 2026-12
  3. What legal disclaimers am I supposed to read?
    The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 25-Mar-2026
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Attn: Simone Montayne
Metadata Manager
3354 College Road
Fairbanks, AK
USA

(907)451-5020 (voice)
(907)451-5050 (FAX)
dggspubs@alaska.gov
Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.9.50 on Wed Mar 25 15:24:42 2026