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Linking Magma Storage and Ascent to Eruption Volume and Composition at an Arc Caldera
Author(s) -
Miller David,
Bennington Ninfa,
Haney Matthew,
Bedrosian Paul,
Key Kerry,
Thurber Clifford,
Hart Laney,
Ohlendorf Summer
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl088122
Subject(s) - sill , geology , caldera , dike , magma , petrology , magma chamber , mafic , volcano , seismology , igneous rock , geochemistry , geophysics
Conceptual models of magma storage and transport under calderas favor a connected system of sills and dikes. These features are individually below the resolution of standard seismic tomography, but radial seismic anisotropy can reveal where they exist in aggregate. We model radial anisotropy at Okmok caldera, Alaska, to demonstrate the presence of a caldera‐centered stacked sill complex and surrounding dike system. We show that ascending magma, inferred from seismicity, either intersects the sill complex, resulting in a larger volume eruption of evolved magma, or bypasses the overlying sill complex via dikes, resulting in a low‐volume mafic eruption. Our results exemplify how the locations of magma storage and paths of transport impact eruption size and composition. As this type of crustal storage is likely common to many calderas, this analysis offers a potential new framework for volcano observatories to forecast the size of impending eruptions.