In a special report, INSIVUMEH stated that a strong explosion at Caliente cone, part of Santa María’s Santiaguito lava-dome complex, occurred at 0629 on 14 August and generated pyroclastic flows that descended the E flank. An ash plume rose about 1.3 km above the complex and drifted S and SW, causing ashfall in San Felipe (15 km SSW), Mazatenango, and Retalhuleu (27 km SW). A moderate explosion on 15 August generated an ash plume that rose 900 m and drifted E. A loud explosion at 0658 on 16 August produced a mushroom-shaped ash cloud that rose 2.5 km and drifted W and SW. Pyroclastic flows traveled 2 km down the San Isidro and Nimá II drainages. Ash fell in San Marcos (10 km SW), Loma Linda (6 km WSW), Palajunoj (18 km SSW), and possibly in multiple fincas including El Faro, La Florida (5 km S), Patzulin (SW flank), and El Patrocinio.

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)