In a special report from 15 April INSIVUMEH stated that activity at Caliente cone, part of Santa María's Santiaguito lava-dome complex, continued at a high level. A loud explosion at 0825 on 15 April was followed by a pyroclastic flow that descended the SE and W flanks of Caliente cone. Collapses of the E and W edges of the crater generated a mushroom-shaped ash cloud that rose 4 km and then drifted 25 km W and SW. Ash fell in areas downwind including Monte Bello, Loma Linda, Las Marías, San Marcos (10 km SW), and Palajunoj (18 km SSW). Cloud cover obscured views during 16-18 April, though during 17-18 April an ash plume from an explosion rose 700 m and drifted SW, causing ashfall in San Marcos Palajunoj. An explosion at 0800 on 19 April generated pyroclastic flows down the SE and W flanks of Caliente cone. Collapses of the E and W edges of the crater generated a mushroom-shaped ash cloud that rose 4.5 km and then drifted 25 km W and SW. Abundant ash fell in the same areas that were affected by the 15-April explosion.

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)