February 2016 – ECUADOR – Two moderately large explosions occurred at the volcano yesterday noon from 12:12 local time. The first and larger explosion produced an ash plume that rose approx. 5000 meters above the summit. The ash plume dispersed mainly to the west and northwest where ash fall occurred in areas including Choglontús, Pillate, Cahuaji and El Manzano.
According to IGEPN, the eruption – which came after a 3 months interval of quiet since last November – was most likely NOT the result of new magma, but instead of accumulated gas pressure in the upper conduit. Magmatic gasses (H2O, CO2 etc) still contained in older magma inside the conduit was being released quietly as the magma continued to cool and crystallize, but most of these gasses were being trapped beneath a solid plug. With time, the gas pressure increased to the critical point: the plug gave way in yesterday’s explosions.
The explosion itself, a typical so-called “vulcanian”-type eruption, was preceded only by a short (lasting little more than an hour), but intense seismic swarm of shallow earthquakes caused by internal fluid movements and rock fracturing as pressurized gasses started to disintegrate the overlying plug. –Volcano Discovery