INSIVUMEH reported constant lava extrusion from Santa María's Santiaguito lava-dome complex on 22 August. At 1745 a series of collapses of the SE crater rim generated pyroclastic flows that reached the S and SE base of the complex. Bombs were ejected 500 m SW and ash plumes rose 4 km. A weak explosion on 23 August generated a white plume that rose 600 m. Ashfall was reported in the Palajunoj region (S).

At 0815 on 24 August a partial collapse of the SE crater rim of Caliente cone was accompanied by an explosion heard 20 km away and a shock wave. The explosion also rattled homes within 10 km. The collapse was followed by pyroclastic flows, avalanches, and more explosions. At 2210 another similar collapse occurred, producing a blast heard 15 km away and pyroclastic flows that descended the SE flank. Houses within 10 km again vibrated. Ash plumes rose as high as 4 km and drifted W and SW. On 25 August explosions continued and block avalanches descended the E flank of Caliente cone. At 0324 on 27 August a moderate explosion produced a mushroom-shaped ash plume that rose 1.3 km, and drifted SW, causing ashfall in Palajunoj. A pyroclastic flow traveled SW, and avalanches traveled S and E. White gas plumes rose 1.2 km.

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)