Geospatial distribution of tephra fall in Alaska: a geodatabase compilation of published tephra fall occurrences from the Pleistocene to the present

Metadata also available as - [Parseable text] - [XML]

Frequently anticipated questions:


What does this data set describe?

Title:
Geospatial distribution of tephra fall in Alaska: a geodatabase compilation of published tephra fall occurrences from the Pleistocene to the present
Abstract:
Tephra fall (volcanic ash) studies are a key component to understanding the frequency and magnitude of volcanic eruptions and conducting volcano-hazard assessments. In addition, many interdisciplinary studies rely on tephra fall deposits as time-stratigraphic markers. Information on tephra deposits in Alaska has previously been dispersed amongst hundreds of publications that span numerous research disciplines. In order to streamline tephra occurrence data, information from these disparate publications have been compiled into one comprehensive geospatial dataset. Pleistocene, Holocene, and historical tephra deposit distribution information has been digitized for more than 120 published resources, including peer-reviewed articles, reports, and theses/dissertations. The dataset includes tephra fall distribution information pertaining to 39 eruptions from at least 19 volcanoes in Alaska. All files can be downloaded free of charge from the DGGS website (<http://doi.org/10.14509/29847>).
Supplemental_Information:
alaska_tephra_contours: polylines representing digitized tephra fall contours 
alaska_tephra_footprints: polygons representing maximum tephra fall distribution extents 
geodiva_stations_12072017: points that represent tephra sample locations 
table_alaska_tephra_contours_figures: list of figures with data that was digitized, with figures attached for user reference 
table_geodiva_samples_12072017: list of tephra samples and metadata 
table_references: list of references for all digitized data 
relationship_classes: geodatabase relationship classes that associate feature classes/tables to each other 
layer-files: layer files provide pre-queried data on deposit contours, maximum distribution footprints, tephra sample locations, and vent locations.
  1. How should this data set be cited?

    Mulliken, K.M., Schaefer, J.R., and Cameron, C.E., 2018, Geospatial distribution of tephra fall in Alaska: a geodatabase compilation of published tephra fall occurrences from the Pleistocene to the present: Miscellaneous Publication MP 164, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 46 p.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -178.817961
    East_Bounding_Coordinate: -104.060291
    North_Bounding_Coordinate: 71.277684
    South_Bounding_Coordinate: 43.359849

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 1964
    Ending_Date: 2016
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a vector data set.

    2. What coordinate system is used to represent geographic features?

      The map projection used is Alaska Albers.

      Projection parameters:
      Standard_Parallel: 55.0
      Standard_Parallel: 65.0
      Longitude_of_Central_Meridian: -154.0
      Latitude_of_Projection_Origin: 50.0
      False_Easting: 0
      False_Northing: 0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.0000000030536018158500163
      Ordinates (y-coordinates) are specified to the nearest 0.0000000030536018158500163
      Planar coordinates are specified in meters

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is GRS 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222101000025.

  7. How does the data set describe geographic features?

    alaska_tephra_contours
    polylines representing digitized tephra fall contours; file type: ArcGIS feature class (Source: Alaska Division of Geological & Geophysical Surveys (DGGS) and Alaska Volcano Observatory)

    tephraname
    Informal name of the tephra unit. (Source: this report)

    Text

    sub_unit
    Contour specific to a subset of the tephra unit (e.g., differences within a deposit thought to represent a specific phase of an eruption, a specific day during a historical eruption, or a distinct feature of a deposit thought to represent a change in the eruption). Value is blank if the contour describes the unit as a whole. (Source: this report)

    Text

    sourcevolc
    If the tephra unit has a known potential source vent. (Source: this report)

    Text

    isopach_cm
    Contour line denotes isopach (equal deposit thickness), given in cm. (Source: this report)

    Text

    mass_gm2
    Contour line denotes isomass (equal mass-per-unit-area of tephra fall), in grams per square meter. (Source: this report)

    Text

    pleth_cm
    Contour line denotes isopleth (equal maximum grain size, pumice size, or lithic size deposition), given in cm (if given, particle type is noted in the map_info field). (Source: this report)

    Text

    map_info
    If the digitized map or illustration contained additional useful metadata, it is detailed here. (Source: this report)

    Text

    comments
    Comments by the digitizer. (Source: this report)

    Text

    citation
    Citation for the reference that the contour was digitized from. (Source: this report)

    Text

    age_epoch
    Age epoch of the deposit/eruption (Pleistocene, Holocene, Alaska historical). (Source: this report)

    Text

    age_in_ref
    Age of deposit/eruption as reported in the reference that the contour is digitized from. (Source: this report)

    Text

    best_age
    This value may be a deposit age estimate provided in a more recent reference or may be the same as the age estimate provided in the reference that the contour was digitized from. (Source: this report)

    Text

    age_cit
    Citation for the reference of the age reported in the best_age field. (Source: this report)

    Text

    age_notes
    Comments on the age determination of the tephra deposit. (Source: this report)

    Text

    fig_num
    Figure number that the contour was digitized from, in the original reference. (Source: this report)

    Text

    fig_scale
    Scale of the figure that the contour was digitized from, in the original reference. (Source: this report)

    Text

    other_cits
    A list of citations for other references that the contour has appeared in. (Source: this report)

    Text

    citationid
    Unique numeric identifier that allows the contour to be linked with the reference it was digitized from. (Source: this report)

    Double

    alaska_tephra_footprints
    polygons representing maximum tephra fall distribution extents; file type: ArcGIS feature class (Source: Alaska Division of Geological & Geophysical Surveys (DGGS) and Alaska Volcano Observatory)

    tephraname
    Informal name of the tephra unit. (Source: this report)

    Text

    sourcevolc
    If the tephra unit has a potential source vent. (Source: this report)

    Text

    citations
    A list of citations for the references that the footprint was derived from. (Source: this report)

    Text

    age_epoch
    Age epoch of the deposit/eruption (Pleistocene, Holocene, Alaska historical). (Source: this report)

    Text

    best_age
    This value may be a deposit age estimate provided in a more recent reference or may be the same as the age estimate provided in the reference that the contour was digitized from. (Source: this report)

    Text

    age_cit
    Citation for the reference of the age reported in the best_age field. (Source: this report)

    Text

    age_notes
    Comments on the age determination of the tephra deposit. (Source: this report)

    Text

    prox_desc
    If available, a proximal description of the deposit. (Source: this report)

    Text

    prox_cit
    Citation for the reference of the proximal deposit description. (Source: this report)

    Text

    dist_desc
    If available, a distal description of the deposit. (Source: this report)

    Text

    dist_cit
    Citation for the reference of the distal deposit description. (Source: this report)

    Text

    comments
    Comments by the digitizer. (Source: this report)

    Text

    footprntid
    Unique numeric identifier that allows the footprint to be linked with the references that it was derived from. (Source: this report)

    Double

    geodiva_stations_12072017
    points that represent tephra sample locations; file type: ArcGIS feature class (Source: Alaska Division of Geological & Geophysical Surveys (DGGS) and Alaska Volcano Observatory)

    stationid
    The alphanumeric descriptor of the sample's station. For samples published without a station identifier, we use the sample's id as a station id. For stations with generic names (1, 2, 3, a, b, c, etc.), we assign the station with the nomenclature: first author last name_publication year_station number. (Source: this report)

    Text

    lat_nad83
    Latitude of sample location, if known (NAD83 datum). Sometimes, these coordinates are imprecise because they were georeferenced from a figure or approximated based on a location description. If so, it is noted in the description. (Source: this report)

    Double

    long_nad83
    Longitude of sample location, if known (NAD83 datum). Sometimes, these coordinates are imprecise because they were georeferenced from a figure or approximated based on a location description. If so, it is noted in the description. (Source: this report)

    Double

    geologist
    Name of the geologist who visited the station and collected the sample, if known. (Source: this report)

    Text

    volcano
    If the station that was visited was on a volcano, the volcano name is specified here. (Source: this report)

    Text

    visitdate
    Date the sample was collected. Sometimes only the year is known. (Source: this report)

    Text

    stationdes
    Text description of the sample locality, if published. If no sample location was published, a specific volcano name or geographic area may be entered. (Source: this report)

    Text

    stationcom
    Comments about the station. (Source: this report)

    Text

    table_alaska_tephra_contours_figures
    list of figures with data that was digitized, with figures attached for user reference; file type: ArcGIS table (Source: Alaska Division of Geological & Geophysical Surveys (DGGS) and Alaska Volcano Observatory)

    CONTENT_TYPE
    Describes the attachment type (image/jpeg for all). (Source: this report)

    Text

    ATT_NAME
    Name of the file that is attached. (Source: this report)

    Text

    DATA_SIZE
    Size of the attachment. (Source: this report)

    Long Integer

    DATA
    Data type. (Source: this report)

    Blob

    table_geodiva_samples_12072017
    list of tephra samples and metadata; file type: ArcGIS table (Source: Alaska Division of Geological & Geophysical Surveys (DGGS) and Alaska Volcano Observatory)

    sampleid
    Alphanumeric descriptor of the sample. For samples with generic names (1, 2, 3, a, b, c, etc.), we assign the sample name with the nomenclature: first author last name_publication year_sample number. (Source: this report)

    Text

    stationid
    The alphanumeric descriptor of the sample's station. For samples published without a station identifier, we use the sample's id as a station id. For stations with generic names (1, 2, 3, a, b, c, etc.), we assign the station with the nomenclature: first author last name_publication year_station number. (Source: this report)

    Text

    at_num
    Alphanumeric ID assigned by the Alaska Tephra Lab. (Source: this report)

    Text

    sourcevolc
    If the tephra unit has a potential source vent. (Source: this report)

    Text

    samp_date
    Date the sample was collected. Sometimes only the year is known. (Source: this report)

    Text

    samptype
    samptype and sampletype2 describe the physical sample type. (Source: this report)

    Text

    samptype2
    samptype and sampletype2 describe the physical sample type. (Source: this report)

    Text

    age_epoch
    Age epoch of the deposit/eruption (Pleistocene, Holocene, Alaska historical). (Source: this report)

    Text

    color
    Color of the sample, if provided. (Source: this report)

    Text

    tephraname
    Informal name of the tephra unit. (Source: this report)

    Text

    alt_tephra
    Some tephra units have been given multiple names, this field provides an alternate tephra name for those samples with multiple tephra unit names. (Source: this report)

    Text

    name_comm
    Comments on the tephra unit name. (Source: this report)

    Text

    sampdes
    Text description of the sample, if published. (Source: this report)

    Text

    sampcom
    Comments about the sample. (Source: this report)

    Text

    table_references
    list of references for all digitized data; file type: ArcGIS table (Source: Alaska Division of Geological & Geophysical Surveys (DGGS) and Alaska Volcano Observatory)

    citationid
    Unique numeric identifier that allows the reference to be linked to derived data. (Source: this report)

    Double

    reference
    Full reference. (Source: this report)

    Text

    relationship_classes
    geodatabase relationship classes that associate feature classes/tables to each other; file type: ArcGIS relationship classes (Source: Alaska Division of Geological & Geophysical Surveys (DGGS) and Alaska Volcano Observatory)

    layer-files
    layer files provide pre-queried data on deposit contours, maximum distribution footprints, tephra sample locations, and vent locations. See accompanying report for detailed listing of the layer files available with this publication.; file type: ArcGIS layer files (Source: Alaska Division of Geological & Geophysical Surveys (DGGS) and Alaska Volcano Observatory)


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?

    As a compilation of previously published data, this project is built on a foundation of work done by other scientists. The list of authors whose work contributed to this database would be too extensive to cite here, but each is credited in the reference table of the dataset. We would like to thank Patricia Gallagher (DGGS), Mike Hendricks (DGGS), and Kristi Wallace (USGS-AVO) for their review of this publication. This project was funded through DGGS cooperative agreements with the USGS Volcano Hazards Program, grant numbers G16AC00054 and G16AC00165. The Alaska Volcano Observatory is a joint program of the U.S. Geological Survey, the Geophysical Institute of the University of Alaska Fairbanks, and the State of Alaska Division of Geological & Geophysical Surveys.

  3. To whom should users address questions about the data?

    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK 99709-3707
    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


Why was the data set created?

Tephra fall (volcanic ash) studies are a key component to understanding the frequency and magnitude of volcanic eruptions and conducting volcano-hazard assessments. In addition, many interdisciplinary studies rely on tephra fall deposits as time-stratigraphic markers. Information on tephra deposits in Alaska has previously been dispersed amongst hundreds of publications that span numerous research disciplines. In order to streamline tephra occurrence data, information from these disparate publications have been compiled into one comprehensive geospatial dataset.


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: 2017 (process 1 of 1)
    Data compilation - As part of an extensive literature review undertaken during population of the Alaska Tephra Database, more than 100 publications containing illustrations or maps with information on the occurrence and distribution of tephra in Alaska were identified. From these publications, approximately 225 figures were saved as individual JPEGs, georeferenced, and contours on the figures were digitized. Tephra contours, footprints, and occurrences were digitized as individual polylines, polygons, and point shapefiles, which were compiled into an ESRI ArcGIS file geodatabase. Relevant metadata garnered from the original publications are documented in tables that now reside in the geodatabase and have established relationships with a table that contains the full references. See accompanying report for additional information about the data compilation methodology and a comprehensive bibliography of data sources.

  3. What similar or related data should the user be aware of?

    Cameron, C.E., and Nye, C.J., 2014, Preliminary database of Quaternary vents in Alaska: Miscellaneous Publication MP 153, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 11 p
    Cameron, C.E., and Schaefer, J.R., 2016, Historically active volcanoes of Alaska: Miscellaneous Publication MP 133 v. 2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 1 sheet


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

  1. How well have the observations been checked?

    This dataset is a compilation of data from numerous publications. Individual publications report geochronologic information in different ways, with no uniform standards, resulting in a variety of formats that make it difficult to design query-friendly age data fields. In addition, as eruption histories are refined with more study and improved dating techniques, so are the ages of specific tephra deposits. Therefore, in this report, we present ages from the original reference that the contour was digitized from, as well as a "best age." Sometimes the original reference is the only age reported and therefore it is also the best age. However, the best age may alternatively be from a more recent publication (i.e., the date reported in the publication with the tephra geospatial information is no longer an accepted age for that deposit/eruption). Ages listed in this dataset are meant to guide researchers, who are encouraged to refer to original publications for more detail on deposit geochronology.

  2. How accurate are the geographic locations?

    This dataset is a compilation of data from numerous publications and thus has limitations. The accuracy of tephra deposit contours is dependent on the original publications from which the tephra fall distributional data were digitized. Table 2 in the accompanying report presents a list of references with figures that were difficult to digitize and tephra fall unit footprints that were difficult to derive. Geospatial accuracy issues arose when contours and sample locations were digitized from very small, manually georeferenced illustrations and map figures. However, these accuracy issues have been mitigated by using landmark cities, vent locations, major geographic features, geopolitical boundaries, roads, and rivers as a means to quality-control digitization of data from small illustrations and maps.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Development of this database is ongoing. As new publications are released that contain tephra distribution data, this dataset compilation will become outdated. The GeoDIVA Alaska Tephra Database is continually updated. Therefore, the static station and samples exported from GeoDIVA on December 7, 2017, and incorporated in this database will eventually be non-comprehensive. We intend to update this dataset to incorporate new data as new datasets are published.

  5. How consistent are the relationships among the observations, including topology?

    Referential integrity among the tables is enforced by the geodatabase system.


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 99709-3707
    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
  2. What's the catalog number I need to order this data set?

    MP 164

  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: 12-Mar-2018
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Attn: Simone Montayne
Metadata Manager
3354 College Road
Fairbanks, AK 99709-3707
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 2.9.21 on Mon Mar 12 14:40:27 2018