Report of Investigation 2017-10, Geologic map of Mount Chiginagak volcano, Alaska, provides 1:25,000 geologic mapping of the Chiginagak volcano. Mount Chiginagak is a hydrothermally active volcano on the Alaska Peninsula, approximately 170 km south-southwest of King Salmon, Alaska. This small stratovolcano, approximately 8 km in diameter, has erupted through Tertiary to Permian sedimentary and igneous rocks. The eruptive products of Chiginagak volcano record a history of chiefly andesite lava flows and associated block-and-ash flows. The oldest lavas exposed are Pleistocene in age and are found everywhere around the edifice except in the northeast sector, where Holocene lava flows dominate the landscape. Holocene activity has covered the northeast flank with rubbly-topped andesite lava flows that extend as far as 4.6 km from their source vent at the summit crater. The farthest-reaching volcanic deposits are on the southeast flank, where block-and-ash-flow, pyroclastic-flow, and lahar deposits extend down valley as far as 9 km from the summit. Limited exposure of deposits of a presumed plinian eruption of middle Pleistocene age indicate at least one episode of explosive activity in Chiginagak's past. This 1:25,000 scale geologic map and accompanying report document the age, geochemical, and spatial distribution of eruptive products of the Mount Chiginagak volcano. Map units are interpreted from field observations, satellite imagery interpretation, geochemical and geochronological analysis. The complete report, geodatabase, and ESRI fonts and style files are available from the DGGS website: http://doi.org/10.14509/29769.
Geologic map of Mount Chiginagak volcano, Alaska
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