Based on satellite imagery, the Washington VAAC reported that ash plumes from Santa María's Santiaguito lava dome complex drifted S on 9 May. INSIVUMEH reported on 10 May that rain caused landslides S down the Nimá Primero river, near the Observatory Vulcanológico de Santiaguito (OVSAN), about 5 km S of the lava dome. Explosions from Caliente dome during 10-11 and 14 May produced gas-and-ash plumes that rose to altitudes of 4.4-5.3 km (14,400-17,400 ft) a.s.l. and drifted SW and E. Ashfall was reported from areas S and SW on 10 May. Avalanches of blocks and ash from the SW edge of Caliente dome were observed on 14 May.

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.

Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH), Washington Volcanic Ash Advisory Center (VAAC)