Microlite Characterization of Basaltic Pumice from Two Plinian Eruptions of Chikurachki Volcano

Abstract:

Plinian eruptions, though rare, are poorly understood volcanic processes. One hypothesis relating to the volcanicity that results in such eruptions require fast ascent to allow gas to remain within the magma, resulting in fragmentation. In unmonitored eruptions the prevailing method to determine ascent rates is to compare microlite textures of experimental and natural samples. We are investigating two mafic Plinian eruptions of the Chikurachki volcano, one from 1853 and an ancient eruption. Preliminary microlite texture analyses showed a notable difference between the two eruptions. Through comparing textures with that of previously analyzed mafic Plinian eruptions, one has shown a similarity to the Fontana deposit of Masaya volcano while the other a similarity to the 122 B.C.E. Mt. Etna eruption. This suggests that the ascent histories of the two mafic Plinian eruptions being studied at Chikurachki volcano are different. This also suggest the cause of the variance in the two eruptions is more complicated than a simple rapid ascent. More work is required on all known mafic Plinian eruptions to try and determine how the magma is able to erupt so explosively.