Project

geochemistry; petrology; physical volcanology; Volcan Llaima; Chilean Andes; Arc volcanism; U-series; subduction

Lead
Petrologists and geochemists concerned with magmatic processes at volcanoes have generally focused their efforts on understanding the origin of magmas in the Earth’s mantle (partial melting) and the compositional evolution of these magmas (differentiation) during ascent prior to eruption. This “ivory tower” approach misses an opportunity to address the eruptive dynamics of active volcanoes with many of the same data that we regularly apply to basic research problems.
Lay summary
Volcan Llaima (38.7° S), the primary focus of this project, is one of the most active volcanoes in the Andean arc, with an average repose period of 3.5 yrs since the onset of reliable historic records (~1850). The other five volcanoes being investigated in this study (36.7-41° S) have erupted since 1835, and there have been four major eruptions in Chile with variably negative consequences since 2008 (two at Llaima). We are combining an extensive characterization of lavas and pyroclastic deposits at Llaima with numerical fluid dynamics modeling in order to find the links between magmatic processes and the processes that trigger eruptions. Arriving at quantitative answers to such questions for specific volcanoes will take many years, but we have made significant progress in this area, in addition to providing new information about magma genesis and evolution in this part of the Andean arc

Direct link to Lay Summary

Last update: 04.02.2013

Number	Title	Start	Funding scheme

Any investigation that leads to a significantly deeper knowledge of arc volcanism is a contribution towards the understanding of a plate tectonic setting of fundamental importance. The Andean arc is a product of one of the world’s classic convergent margins, and we stress throughout this proposal that Llaima has a number of special attributes which make it a particularly advantageous subject for the ambitious and multifaceted project that we propose, and for resolving important problems that we are addressing. Llaima is a useful counterpart to the much more complicated and long-lived magmatic record at Tatara-San Pedro. The relative simplicity of both magma genesis and differentiation at Llaima, in combination with the unprecedented geochemical data set that we propose to collect, will allow us to generate unusually well quantified petrologic models for both the origin and evolution of magmas in the Andean Southern Volcanic Zone, and these will serve as end-member reference modes for magmatic processes and components in this arc. The outcome of numerical modeling of the last four centuries of Strombolian activity at Llaima will be knowledge of the physical processes controlling the explosive potential of this volcano. This has implications at the national level owing to the high potential of any Strombolian eruption at Llaima to trigger far-reaching lahars, and to similarities with activity at near-by Villarrica. Our insights into the relationships among crystal content, magma stagnation, magma recharge, and eruptive mode may be broadly applicable and may shed light on the mechanisms that control the onset and unfolding of a canonical style of eruptive activity. We hope that these results will be incorporated into eruption forecasting methodology.