INSIVUMEH reported that on most days during 15-22 July the active lava dome of Santiaguito was visibly degassing and generating plumes. Ash was noted on16 and 20 July rising up to 3.2 km (10,500 ft) a.s.l. and tendeding to drift SW. On most days, fumarolic colums reached 2.8-3.2 km (9,200-10,500 ft) a.s.l. and weak to moderate avalanches flowed towards Canyon Nima River I. A moderate explosion occurred 16 July, and ashfall was reported in the Finca El Rosario Palajunoj.

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)