INSIVUMEH reported that high-level eruptive activity continued at Santa Maria’s Santiaguito lava-dome complex during 25 June-2 July with lava extrusion, block collapses, and avalanches at the Caliente dome complex. The continuous effusion of blocky lava produced block avalanches on the dome’s flanks and occasional short pyroclastic flows that descended multiple flanks, creating promontories of unstable material. Incandescence from avalanches of material at the dome as well as explosions was visible during most nights and early mornings, and occasional incandescence was also present along the upper parts of the lava flow on the WSW flank. Lava extrusion fed the upper parts of the lava flow, and block avalanches occasionally traveled over the lava flow. Daily explosions (a few per hour on most days) generated gas-and-ash plumes that rose 700-900 m above the summit and drifted mainly NW, W, and SW. Ashfall was reported in San Marcos (8 km SW) and Loma Linda Palajunoj (7 km SW) during 26-27 June. Rain caused steam to rise from the lava flows in the Zanjón Seco (SW) and San Isidro (W) drainages during 29-30 June. On 1 July a lahar descended the Cabello de Ángel river, a tributary of the Nimá I, on the SE flank, carrying tree trunks, branches, and volcanic blocks up to 1 m in diameter. Weather conditions sometimes prevented visual observations.

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)