| Summary: | Giving continuity to the eruptive process of Galeras volcano detected about middle of 2004, after the intrusion of a lava dome in 2006, and the occurrence of explosive eruptions in July 12 of the same year and January 17 of 2008, new magmatic material was observed in September, 2008, joining the remnants of the 2006 dome, with an estimated volume 3 towards the end of 2008, near to 5.000.000 m, restarting a new cycle of eruptive explosive processes, three of them within one month. These eruptions, in February 14 and 20 and March 13 of 2009, threw juvenile magma (with high glass contains), with the particularity of exhibiting before and at a few hours, a decrease in the seismicity, specially that one associated with transit of fluids as well as the decrease in the emissions of Sulphur Dioxide, SO . Although it was 2 no record of "Screw" type events, there were observed "hybrid" earthquakes with a fracture component, of superficial source. The presence of a lava dome, the cooling and partial solidification of the magma column with the consequent sealing of conduits, avoiding the free escape of gases, could explain the mechanism of beginning of these eruptions and with it, the behavior observed in seismicity and SO2. In comparative terms, the seismic energy liberated by the eruptions of the current cycle of reactivation, allows to establish from bigger to minor degree, the following order: Nov/21/04, Aug/21/04, Feb/20/09, Mar/13/09, Jan/17/08, Feb/14/09, Jul/12/06, Aug/11/04 and Nov/24/05. The total volume considered as minimum deposited by the 3explosive eruptions between 2004 and 2009 is near to 6.500.000 m , of which, almost a 38% 3 (2.500.000 m ) corresponds to the 2009 eruptions. Galeras continues presenting fluctuations in its activity, framed in the mobilization of the major volume of magmatic material of 20 years ofpermanent monitoring.
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