Based on seismic data and visual observations, INSIVUMEH reported that on 27 June a 16-m-wide, 90-cm-deep lahar traveled down Santa María's Rio Nima I drainage, carrying rocks up to 80 cm in diameter. During 28-29 June block avalanches again traveled down the SE flank and fumarolic plumes drifted SW. During 1-3 July explosions produced ash plumes that rose 700 m above the crater and drifted SW. Ashfall was reported in La Florida (5 km S) and Monte Claro (S). Avalanches from lava flow fronts descended the SW flank.

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)