Variations in eruption style during the 1931 A.D. eruption of Aniakchak volcano, Alaska

Journal of Volcanology and Geothermal Research
By: , and 



The 1931 A.D. eruption of Aniakchak volcano, Alaska, progressed from subplinian to effusive eruptive style and from trachydacite to basaltic andesite composition from multiple vent locations. Eyewitness accounts and new studies of deposit stratigraphy provide a combined narrative of eruptive events. Additional field, compositional, grain size, componentry, density, and grain morphology data document the influences on changing eruptive style as the eruption progressed. The eruption began on 1 May 1931 A.D. when a large subplinian eruption column produced vesicular juvenile-rich tephra. Subsequent activity was more intermittent, as magma interacted with groundwater and phreatomagmatic ash and lithic-rich tephra was dispersed up to 600 km downwind. Final erupted products were more mafic in composition and the eruption became more strombolian in style. Stratigraphic evidence suggests that two trachydacitic lava flows were erupted from separate but adjacent vents before the phreatomagmatic phase concluded and that basaltic andesite lava from a third vent began to effuse near the end of explosive activity. The estimated total bulk volume of the eruption is 0.9 km3, which corresponds to approximately 0.3 km3 of magma. Eruption style changes are interpreted as follows: (1) a decrease in magma supply rate caused the change from subplinian to phreatomagmatic eruption; (2) a subsequent change in magma composition caused the transition from phreatomagmatic to strombolian eruption style. Additionally, the explosion and effusion of a similar magma composition from three separate vents indicates how the pre-existing caldera structure controlled the pathway of shallow magma ascent, thus influencing eruption style.

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Publication type Article
Publication Subtype Journal Article
Title Variations in eruption style during the 1931 A.D. eruption of Aniakchak volcano, Alaska
Series title Journal of Volcanology and Geothermal Research
DOI 10.1016/j.jvolgeores.2011.08.002
Volume 207
Issue 3-4
Year Published 2011
Language English
Publisher Elsevier
Publisher location Amsterdam, Netherlands
Contributing office(s) Alaska Volcano Observatory
Description 14 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Volcanology and Geothermal Research
First page 69
Last page 82
Country United States
State Alaska
Other Geospatial Aniakchak Volcano
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