Dynamics of volcanic eruptions Research Papers (original) (raw)

Planchón-Peteroa volcano started a renewed eruptive period between January 2010 and July 2011. This eruptive period was characterized by the occurrence of 4 explosive eruptive phases, dominated by low-intensity phreatic activity, which produced almost permanent gas/steam columns (200-800 m height over the active crater). Those columns presented frequently scarce ash, and were interrupted by phreatic explosions that produced ash columns 1,000-3,000 m height in the more intense periods. Eruptive plumes were transported in several directions (NW, N, NE, E and SE), but more than half of the time the plume axis was 130-150° E, and reached a distance up to 638 km from the active crater. Tephra fall deposits identified in the NW, N, NE, E and SE flanks covered an area of 1,265 km 2 , thickness variable from 4 m (SE border of active crater) to ~0.5 cm 36.8 km SE and ~8 km NW from active crater, respectively, corresponding to a minimum volume of 0.0088 km 3. Tephra fall deposit is exclusively constituted of no juvenile fragments including: lithics fragments as main component, quartz and plagioclase crystals, some oxidized lithics, and occasional presence of Fe oxide, and less frequently Cu minerals, as single fragments. We present new field-based measurements data of the geochemistry of gas/water from fumaroles and acid crater lakes, and fall deposit analysis, that integrated with the eruptive record and GOES satellite data, suggests that the eruptive period 2010-2011 has been related to an increasing of heat and mass transfer from hydrothermal-magmatic reservoirs, which would have been favoured by the formation and/or reactivation of cracks after 8.8 Mw Maule earthquake in February 2010. This process also allowed the ascent of fluids from a shallow hydrothermal source, dominated by reduced species as H 2 S and CH 4 , during the entire eruptive period, and the release of more oxidizing fluids from a deep magmatic reservoir, dominated by acid species as SO 2 , HCl and HF, increasing strongly after the end of the eruptive period, probably since October 2011. The eruptive period was scored with a magnitude of 3.36, corresponding to a VEI 1-2.