HR: 1330h
AN: V42B-0349    [PDF]
TI: Remotely Induced Eruptions: the Caldera-Forming Eruption of Fisher Volcano
AU: * Stelling, P
EM: afpls1@uaa.alaska.edu
AF: University of Alaska Anchorage, Beatrice McDonald Building, rm. 206 3211 Providence Dr., Anchorage, AK 99508 United States
AU: Gardner, J
EM: gardner@mail.utexas.edu
AF: University of Texas at Austin, Geological Science Department 1 University Station C1100, Austin, TX 78712-0254 United States
AU: Beget, J
EM: ffjeb1@uaf.edu
AF: University of Alaska Fairbanks, 903 Koyukuk Dr. UAF/GI, Fairbanks, AK 99775-7320 United States
AB: The caldera-forming eruption (CFE) of Fisher Volcano, Alaska, occurred in three major phases: a Plinian eruption of dacitic pumice from a northern vent, followed by a compositionally diverse pyroclastic flow from the same northern vent, and finally another Plinian eruption of a different dacite from a separate southern vent. Juvenile material within the pyroclastic flow consists of the northern dacite (67 wt.% SiO$_{2}$), basaltic andesite (54 wt.% SiO$_{2}$), and banded clasts showing liquid-liquid mingling of these two magmas. The southern dacite (63 wt.% SiO$_{2}$) shows no indication of contact with the northern dacite or basaltic andesite, and is compositionally and genetically distinct from these magmas. The physical, chemical and textural separation of the southern dacite from the northern CFE magmas indicates that these magmas occupied separate magma reservoirs prior to eruption. Temporal relationships deduced from field exposures indicate that the eruption of the southern dacite was the final component of the CFE sequence and was contemporaneous with piecemeal caldera collapse. Combined, these data suggest that the violent northern eruption stimulated the unconnected southern magma system and induced an eruption. This marks one of few (if not the only) descriptions of one eruption provoking the eruption of an unrelated system, and may call for the re-interpretation of other significant volcanic sequences.
DE: 8414 Eruption mechanisms
DE: 8439 Physics and chemistry of magma bodies
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting