Abstract

The first of four phases observed in the eruption on the western coast of Lopevi was marked by explosive activity during which the old crater reopened and a new crater, referred to as the upper crater, was formed. A smoke avalanche carrying scoria, lapilli, and cinders spread subhorizontally and represented the second phase. In the third phase, four lava flows containing jagged, scoriaceous blocks 10-50 cm in diameter were emitted from the base of the upper crater, covering part of the deposits of the smoke avalanche. The fourth phase was marked by the opening of several new vents characterized by activity involving the emission of either gaseous jets, alternating smoke wreaths and loud explosions, or gaseous clouds and lava flows from lower craters accompanied by a decrease in the activity in the upper crater. Petrographic analysis of the lavas shows that they are andesitic basalts containing plagioclase and forsterite phenocrysts and plagioclase microlites. Petrogenic evidence shows that the rocks of this eruption resemble the series of alkalic olivine-bearing basalts, and in some cases possess characteristics similar to the tholeiitic series.

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