INSIVUMEH reported that the eruption at Santa María’s Santiaguito lava-dome complex continued during 2-9 May. Effusion from the Caliente dome complex fed lava flows that descended the San Isidro and Zanjón Seco drainages on the W and SW flanks; the main lava flow was 4.3 km long and remained active. Daily weak-to-moderate explosions generated ash-and-steam plumes that generally rose as high as 800 m and drifted SW. The explosions were also accompanied by block-and-ash flows that descended multiple flanks of the dome. Incandescence from the dome and the lava flows was visible each morning and night. Avalanches of material from the lava-flow front and margins caused ash plumes around the flanks. Activity during 5-6 May was characterized by high levels of extrusive and explosive activity; 40 explosions were recorded, producing ash plumes that rose 3.5 km above the dome and drifted SW. Ashfall was reported in San Marcos Palajunoj (8 km SW), Loma Linda (7 km W), and other nearby communities. During 6-7 May quiet rumbling sounds were heard on nearby farms. Residents were warned to stay 6 km away from the lava-dome complex.

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)