Abstract
Measuring the amount of magma intruding in a volcano represents one of the main challenges of modern volcanology. While in closed-vent volcanoes this parameter is generally assessed by the inversion of deformation data, in open-vent volcanoes its measurement is more complicated and results from the balance between the magma entering and leaving the storage system. In this work we used thermal and SO2 flux data, derived from satellite measurements, to calculate the magma input and output rates of Mt. Etna between 2004 and 2010. We found that during the analysed period more magma was supplied than erupted, resulting into an endogenous growth rate equal to 22.9 ± 13.7 × 106 m3 y−1. Notably, this unbalance was not constant in time, but showed phases of major magma accumulation and drainage acting within a compressible magma chamber. The excellent correlation with the inflation/deflation cycles measured by ground-based GPS network suggests the thermal, SO2 flux and deformation data, can be combined to provide a quantitative analysis of magma transport inside the shallow plumbing system of Mt Etna. Given the global coverage of satellite data and the continuous improvement of sensors in orbit, we anticipate that this approach will have sufficient detail to monitor, in real time, the endogenous growth associated to other world-wide open-vent volcanoes.
Highlights
The rate at which deeply-sourced magma enters a magmatic system and the rate at which it comes out of it are two essential parameters for estimating the endogenous growth of a volcano and for predicting its behaviour in the future[1]
The low thermal regime, characterized by Volcanic Radiative Power (VRP) < 40 MW ( < 7.6 log-transformed), was typical of inter-eruptive periods, when the thermal source was likely produced by weak strombolian activity, hot degassing cracks within the summit craters, as well as by the cooling of previously emplaced lava flows
The magma supply rate and the magma output rate have been estimated using eqs 1 and 2, whose detailed parametrization is described in the method section
Summary
The rate at which deeply-sourced magma enters a magmatic system (magma supply rate) and the rate at which it comes out of it (magma output rate) are two essential parameters for estimating the endogenous growth of a volcano and for predicting its behaviour in the future[1]. The magma supply rate (Qin) is classically estimated from gas flux data (mainly sulphur dioxide), by using the so-called “petrologic method”[3,4]. The magma output rate (Qout) is instead calculated from repeated measurements of volumes erupted over discrete time intervals, or through a space-based thermal approach[5] The latter, called “thermal proxy”, derives www.nature.com/scientificreports/. Where ρlava (kg m−3) is the bulk densities of the lava flow and crad (J m−3) is an empirical best-fit parameter that relates the lava discharge rate to the thermal radiation for any given rheological case[8]
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