INSIVUMEH reported that on 29 August fumarolic plumes from Santa María's Caliente dome rose 250-300 m and drifted SE. Small avalanches were active on the S part of the dome. Explosions on 3 September produced ash plumes that rose 200-800 m above Caliente dome and drifted W and SW. Four active lava flows generated block avalanches that traveled S down the Rio Nima I and Rio Nima II drainages. On 4 September hot lahars traveled S down the Rio Nima I and San Isidro drainages. The lahar in the San Isidro channel was 30 m wide and 2 m deep, emitted a sulfur odor, and carried blocks up to 1 m in diameter.

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)