The 2008 phreatomagmatic eruption of Okmok Volcano, Aleutian Islands, Alaska: Chronology, deposits, and landform changes

Okmok volcano, Aleutian Islands, Alaska, explosively erupted over a five-week period between July 12 and August 23, 2008. The eruption was predominantly phreatomagmatic, producing fine-grained tephra that covered most of northeastern Umnak Island. The eruption had a maximum Volcanic Explosivity Index (VEI) of 4, with eruption column heights up to 16 km during the opening phase. Several craters and a master tuff cone formed in the caldera as a result of phreatomagmatic explosions and accumulated tephra-fall and surge deposits. Ascending magma continuously interacted with an extensive shallow groundwater table in the caldera, resulting in the phreatomagmatic character of the eruption. Syneruptive explosion and collapse processes enlarged a pre-existing lake, created a second, entirely new lake, and formed new, deep craters. A field of ephemeral collapse pits and collapse escarpments formed where rapid groundwater withdrawal removed material from beneath capping lava flows. This was the first significant phreatomagmatic event in the U.S. since the Ukinrek Maars eruption in 1977. This digital data release provides GIS files of field station locations and various geographic features described in the accompanying report.

Data and Resources

Field Value
access_constraints ["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.", "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)."]
bbox-east-long -166.463118
bbox-north-lat 53.953138
bbox-south-lat 53.199696
bbox-west-long -168.340761
contact-email dggsgis@alaska.gov
coupled-resource []
dataset-reference-date [{"type": "publication", "value": "2015-01-01"}]
frequency-of-update notPlanned
licence ["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."]
metadata-date 2015-04-09
metadata-language eng; USA
metadata_type geospatial
progress completed
resource-type dataset
responsible-party [{"name": "Alaska Division of Geological & Geophysical Surveys", "roles": ["pointOfContact"]}]
spatial {"type": "Polygon", "coordinates": [[[-168.340761, 53.199696], [-166.463118, 53.199696], [-166.463118, 53.953138], [-168.340761, 53.953138], [-168.340761, 53.199696]]]}
spatial_harvester true
temporal-extent-begin 2008-01-01
temporal-extent-end 2014-01-01
Groups
  • AmeriGEOSS
  • National Provider
  • North America
Tags
  • active-volcanoes
  • aleutian-arc
  • aleutian-islands
  • amerigeo
  • amerigeoss
  • ash-cloud
  • ash-fall
  • caldera
  • ckan
  • cone-a
  • cone-b
  • cone-c
  • cone-d
  • cone-e
  • cone-f
  • cone-g
  • cone-h
  • cone-i
  • cone-j
  • fort-glenn
  • geo
  • geologic-hazards
  • geomorphology
  • geoss
  • geothermal
  • groundwater
  • heat-flow-study
  • historic-eruption
  • holocene
  • lahar
  • lahar-runout-flow
  • lake-level
  • mount
  • national
  • north-america
  • okmok
  • okmok-caldera
  • okmok-hot-springs
  • okmok-volcano
  • stratigraphy
  • surface-water
  • tephra
  • umnak-island
  • umnak-quadrangle
  • unalaska-quadrangle
  • united-states
  • volcanic-ash
  • volcanic-eruption
  • volcaniclastics
  • volcanology
isopen False
metadata_created 2025-11-22T02:49:06.567365
metadata_modified 2025-11-22T02:49:06.567369
notes Okmok volcano, Aleutian Islands, Alaska, explosively erupted over a five-week period between July 12 and August 23, 2008. The eruption was predominantly phreatomagmatic, producing fine-grained tephra that covered most of northeastern Umnak Island. The eruption had a maximum Volcanic Explosivity Index (VEI) of 4, with eruption column heights up to 16 km during the opening phase. Several craters and a master tuff cone formed in the caldera as a result of phreatomagmatic explosions and accumulated tephra-fall and surge deposits. Ascending magma continuously interacted with an extensive shallow groundwater table in the caldera, resulting in the phreatomagmatic character of the eruption. Syneruptive explosion and collapse processes enlarged a pre-existing lake, created a second, entirely new lake, and formed new, deep craters. A field of ephemeral collapse pits and collapse escarpments formed where rapid groundwater withdrawal removed material from beneath capping lava flows. This was the first significant phreatomagmatic event in the U.S. since the Ukinrek Maars eruption in 1977. This digital data release provides GIS files of field station locations and various geographic features described in the accompanying report.
num_resources 5
num_tags 50
title The 2008 phreatomagmatic eruption of Okmok Volcano, Aleutian Islands, Alaska: Chronology, deposits, and landform changes