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

Frequently anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

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:

   • <http://doi.org/10.14509/29847>

   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)
   • Mulliken, K.M.
   • Schaefer, J.R.
   • Cameron, C.E.

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:

   • <http://doi.org/10.14509/27357>

   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:

   • <http://doi.org/10.14509/20181>

   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?
   • Availability in non-digital form:

     DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media by mail, phone, fax, or email from the DGGS Fairbanks office. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for the exact shipping amount.

   • Cost to order the data: Contact DGGS for current pricing

   • Availability in digital form:

     Data format:	Geodatabase, ArcMap document, and ArcGIS layer files
     Network links:	<http://doi.org/10.14509/29847>

   • Cost to order the data: Free download

Who wrote the metadata?

Dates:

Last modified: 22-Jun-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:

• <http://www.dggs.alaska.gov/metadata/dggs.ext>