The volcano-tectonic history of the Maninjau caldera, Western Sumatra, Indonesia

Abstract

Recent investigations help elucidate the volcano-tectonic history of Mt. Maninjau, Sumatra. Three stages may be distinguished: the pre-volcanic edifice stage, the pre-caldera stage and the caldera-formation stage. During the pre-caldera stage, fissures opened in this part of Sumatra as a result of stresses, the largest presumably being vertical. In the next stage basaltic to andesitic magma ascended to the surface, building up a number of strato-volcanoes, one of which formed the N-S oriented Maninjau compound volcanic complex. The caldera-formation stage was preceded by the ejection of some 220-250 km3 of pumiceous tuff. This was subsequently followed by the collapse of the 1op part of the volcano, and the radial failure of the western flank. Two eruptions of acid magma have taken place, the first yielding an unwelded and the second a welded tuff. the latter presumably ejected from the southernmost crater. Since then, obvious volcanic activity has ceased at Mt. Maninjau.