Geology of Kasatochi volcano, Aleutian Islands, Alaska
Dates
Publication Date
2017
Start Date
2008
End Date
2017
File Modification Date
2017-08-08 12:08:00
Citation
Nye, C.J., Scott, W.E., Neill, O.K., Waythomas, C.F., Cameron, C.E., and Calvert, A.T., 2017, Geology of Kasatochi volcano, Aleutian Islands, Alaska: Alaska Division of Geological & Geophysical Surveys, http://doi.org/10.14509/29718.
Summary
Kasatochi is a small, isolated island volcano in the center of the Aleutian Island chain. It consists of a roughly circular cone approximately 3 km in diameter with a lake-filled central crater that is 1.2 km in diameter and extends from the highest point on the island to sea level. The oldest unit recognized is a thick series of mid-Pleistocene glaciovolcanic deposits consisting of autobrecciated lava, lahars, and volumetrically minor lava masses that we believe to have been emplaced underneath a regional ice cap. This unit is unconformably overlain by several massive Holocene lavas, above which lies a thick sequence of latest-Holocene pyroclastic deposits likely deposited during the crater-forming eruption. The 2008 eruption enlarged [...]
Summary
Kasatochi is a small, isolated island volcano in the center of the Aleutian Island chain. It consists of a roughly circular cone approximately 3 km in diameter with a lake-filled central crater that is 1.2 km in diameter and extends from the highest point on the island to sea level. The oldest unit recognized is a thick series of mid-Pleistocene glaciovolcanic deposits consisting of autobrecciated lava, lahars, and volumetrically minor lava masses that we believe to have been emplaced underneath a regional ice cap. This unit is unconformably overlain by several massive Holocene lavas, above which lies a thick sequence of latest-Holocene pyroclastic deposits likely deposited during the crater-forming eruption. The 2008 eruption enlarged the preexisting crater, and produced pyroclastic density currents, surges, and fall that blanketed the entire island except for the crater wall and steep, seaward-facing cliffs on the flanks. 2008 deposits initially extended the shoreline seaward by up to 500 m. A multidisciplinary effort to document recovery of the ecosystem was initiated, and this study of the geology of the island was undertaken as part of that effort. This collection of electronic data is a supplement to the Geology of Kasatochi volcano, Aleutian Islands report and geologic map. It provides spreadsheets of sample metadata and major and trace element XRF and ICP/MS data which are included in the appendices; electron microprobe mineral analyses which are discussed in the report, but not tabulated elsewhere; and high resolution versions of panoramic photographs (appendix 1) and photomicrographs (appendix 7).
Kasatochi volcano is located at the intersection of the flat, shallow Aleutian platform and the Bering slope rise, an area of high biologic productivity. As a result, the island hosts a large sea lion colony and nesting sites for hundreds of thousands of seabirds. A large eruption in 2008 blanketed the island in pyroclastic deposits, covering nesting sites and almost all existing vegetation. A multidisciplinary effort to document recovery of the ecosystem was initiated, and this study of the geology of the island was undertaken as part of that effort. This study is the first to document the geology of the entire island, and presents a snapshot of the island early in its response to the 2008 eruption.
