INSIVUMEH reported that eruptive activity continued at Santa Maria’s Santiaguito lava dome complex during 12-19 September. Incandescence from the dome was visible during most nights and early mornings, and occasionally from the lava flow on the WSW flank. Lava extrusion continued. Daily weak-to-moderate explosions generated gas-and-ash plumes that rose 900-1,000 m above the dome and drifted NW, W, and SW. Some explosions triggered incandescent avalanches that descended the dome’s flanks in all directions, and occasionally into drainages on the S, SE, and E flanks. Deposits from block-and-ash-flows accumulated on top of the lava flows in the Zanjón, Seco, and San Isidro drainages.

Geological Summary. Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing E towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)