INSIVUMEH reported that during 24-30 March weak explosions at Santa María’s Santiaguito lava-dome complex generate ash plumes that rose to 2.8-3.4 km (9,000 ft-11,000 ft) a.s.l. and drifted W, NE, SW. Collapses of blocky lava from the Caliente dome sent avalanches on the S and SW flank of the Caliente dome, causing minor ashfall around the volcano. Block avalanches were also observed on the E and S flanks; ashfall was reported in San Marcos (8 km SW) and Loma Linda Palajunoj (6 km WSW) on 25 and 27 March. Minor pyroclastic flows were reported on 28 March.

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)