May 2015 – NICARAGUA – After a week of calm, a new phase of explosive activity occurred yesterday at the volcano, beginning with a moderately large explosion at 12:02 local time. An ash plume rose approx. 3 km above the summit: Several smaller explosions and phases of calm ash venting followed this event. Ash falls were noted in up to 15 km distance to the SW, in areas of the villages Posolega and Quezalguaque.
So far it is unclear whether the explosions are the result of phreatic or hydrothermal activity, i.e. caused by pressurized fluids in the shallow hydrothermal system, or whether they are result of new magma reaching the surface.
For now, INETER has not found evidence of fresh magmatic material in the deposits of the explosions – all ash and blocks are fragmented older rocks from near the surface – and the accompanying seismicity has been very shallow. This would favor the first scenario. –Volcano Discovery