A basalt trigger for the 1991 eruptions of Pinatubo volcano?

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THE eruptive products of calc-alkaline volcanos often show evidence for the mixing of basaltic and acid magmas before eruption (see, for example, refs 1, 2). These observations have led to the suggestion3 that the injection of basaltic magma into the base of a magma chamber (or the catastrophic overturn of a stably stratified chamber containing basaltic magma at its base) might trigger an eruption. Here we report evidence for the mixing of basaltic and dacitic magmas shortly before the paroxysmal eruptions of Pinatubo volcano on 15 June 1991. Andesitic scoriae erupted on 12 June contain minerals and glass with disequilibrium compositions, and are considerably more mafic than the dacitic pumices erupted on 15 June. Differences in crystal abundance and glass composition among the pumices may arise from pre-heating of the dacite magma by the underlying basaltic liquid before mixing. Degassing of this basaltic magma may also have contributed to the climatologically important sulphur dioxide emissions that accompanied the Pinatubo eruptions.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title A basalt trigger for the 1991 eruptions of Pinatubo volcano?
Series title Nature
Volume 356
Issue 6368
Year Published 1992
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Nature
First page 426
Last page 428
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