In a special report posted on 19 June, INSIVUMEH reported that a strong explosion at Caliente cone, part of Santa María's Santiaguito lava-dome complex, occurred at 0512 and generated pyroclastic flows and an ash plume that rose 5 km and drifted 40-50 km W, SW, and S. Ashfall was reported in multiple farms and towns including San Marcos (10 km SW), Loma Linda, Palajunoj (18 km SSW), El Faro (SW flank), Patzulin (SW flank), El Patrocinio, El Palmar (12 km S), San Felipe (15 km SSW), and Las Marías. A loud explosion at 2239 on 20 June generated an ash plume containing lightning that rose 2.5 km. Shock waves were detected in areas within 15 km. Pyroclastic flows traveled 2 km down the W, S, and E sides of Caliente cone. Abundant gas emissions were visible the next day.

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)