Multidisciplinary observations of the 2011 explosive eruption of Telica volcano, Nicaragua: Implications for the dynamics of low-explosivity ash eruptions

We present multidisciplinary observations of the March-June 2011 VEI 2 eruptive episode of the basaltic-andesite Telica volcano, Nicaragua, which allow for a comprehensive study of the eruption mechanics of low-explosivity eruptions at persistently active volcanoes. The observations are from a dense network of seismic and GPS instrumentation augmented by visual observations of the eruptive episode, geochemical and petrologic analysis of eruptive products, plume SO₂ measurements, and temperature measurements of fumaroles inside and outside the active vent. The 2011 eruptive episode was Telica's most explosive since 1999 and consisted of numerous vulcanian explosions, with maximum column heights of 1.5-2km above the crater rim, depositing a low volume of dominantly hydrothermally altered ash. Based on observed variations in seismicity, temperature, and SO₂ flux, the lack of deformation of the edifice, the non-juvenile origin of and predominance of accretionary lapilli in the ash, we propose that temporary sealing of the hydrothermal system between ~0.5 and 2km depth, allowed pressure to build up prior to vulcanian explosions, making this a phreatic eruptive episode.