On 4 July, INSIVUMEH reported that an explosion from Santa María's Santiaguito lava dome complex produced an ash plume that rose to an altitude of 3.3 km (10,800 ft) a.s.l. and drifted SW. A lahar traveled S down the Nima I river, carrying tree limbs and blocks up to 50 cm in diameter. On 7 and 8 July, sounds resembling avalanches descending the flanks were reported; visual observations were hindered due to cloud cover.

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)