Tephra samples and analyses from the 2018-2023 eruption of Semisopochnoi Volcano, Alaska

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Frequently anticipated questions:


What does this data set describe?

Title:
Tephra samples and analyses from the 2018-2023 eruption of Semisopochnoi Volcano, Alaska
Abstract:
Tephra samples and analyses from the 2018-2023 eruption of Semisopochnoi Volcano, Alaska, Raw Data File 2025-15, includes samples and analyses collected from the 2018-2023 eruption of Semisopochnoi volcano in the western Aleutian Islands, Alaska. Samples were collected during two field visits: May 30 to June 1, 2021, and June 10, 2023. A total of sixteen samples were collected across Semisopochnoi Island at varying distances from the eruption source, the north crater of Mount Young. Samples were collected from the surface on snow, grass, or other substrates that suggested deposition during recent eruptive activity but are, in all cases, aggregates of prior eruption events up to the sample date and may contain minor wind-blown contamination from older surfaces. These data and report are available from the DGGS website: http://doi.org/10.14509/31645 and a subset of the results are archived in the Geologic Database of Information on Volcanoes in Alaska (GeoDIVA; Cameron and others, 2022, doi.org/10.14509/geodiva).
Supplemental_Information: >data: Analytical lab data and accompanying data dictionary
  1. How might this data set be cited?
    Loewen, M.W., Dietterich, H.R., Lubbers, Jordan, and Van Eaton, A.R., 2025, Tephra samples and analyses from the 2018-2023 eruption of Semisopochnoi Volcano, Alaska: Raw Data File RDF 2025-15, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 13 p.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: 179.492357
    East_Bounding_Coordinate: 179.729819
    North_Bounding_Coordinate: 52.001188
    South_Bounding_Coordinate: 51.917959
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2021
    Ending_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 WGS84.
      The ellipsoid used is WGS 84.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257223563.
  7. How does the data set describe geographic features?
    rdf2025_015_data.xlsx, rdf2025_015_data_dictionary.xlsx
    Analytical lab data and accompanying data dictionary (Source: DGGS)

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?
    Field sampling in 2021 and 2023 was conducted in association with Alaska Volcano Observatory geophysical monitoring network maintenance, with logistical support from field engineers on the joint mission. The 2021 work was supported by the crew of the R/V Steadfast and helicopter pilot Mike Grover. The 2023 work was supported by the crew of the R/V Tiglax. Simone Montayne provided metadata review. Kristi Wallace, Cheryl Cameron, and Scott Crass provided data and subject matter metadata review. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  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?

These data describe the nature of samples from a past eruption to aid in discussing Alaska volcanism's spatial and temporal patterns. In addition, the work supports improvements to eruption scenario forecasts and hazard response.

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)
    Sample collection - Samples were collected in 2021 and 2023. Locations were recorded using tablet-integrated GPS with an accuracy of approximately 10 meters. In early summer 2021, ash deposits forming a distinct layer atop clean snow from winter 2020 through spring 2021 were sampled at three field sites. Two sites (21SMHD19 and 21SMHD07) were sampled within 30 x 30 cm squares, and one site (21SMHD12B) within a 20 x 20 cm square. Ash and snow were placed in gallon-sized sealable plastic bags, gravity-filtered using Whatman 541 filter paper, and dried at 40-50 degrees C for over 24 hours prior to weighing. Station identifiers (StationID) were assigned to sample locations and general observation sites. Sample identifiers (SampleID) refer to individual samples and include descriptive details. Laboratory identification numbers (at_num) were assigned during processing and analysis.
    Date: 2025 (process 2 of 2)
    Analytical methods - Grain size distributions for nine bulk samples were assessed using three techniques: standard sieving, laser diffraction particle size analysis, and dynamic image analysis. Tephra samples were embedded in epoxy and polished for electron probe microanalysis (EPMA) at the Alaska Tephra Laboratory. EPMA was conducted at the University of Alaska Fairbanks Advanced Instrumentation Laboratory using a JEOL JXA 8530F electron microprobe. For each sample, polished epoxy mounts were prepared for three particle size fractions: 63-125 micrometer, 125-250 micrometer, and 250-500 micrometer. These fractions were qualitatively examined using a JEOL 6510LV scanning electron microscope at the Alaska Tephra Laboratory.
  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:

    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

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?
    Sample location coordinates were obtained using recreational-grade GPS units, with a typical reported accuracy of about 10 meters.
  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 2025-15
  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: 01-Aug-2025
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 Fri Aug 01 17:49:05 2025