INSIVUMEH reported that the eruption at Santa María’s Santiaguito lava-dome complex continued during 12-18 April. 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. Incandescence from the dome and the lava flows was frequently visible at night. Avalanches down the N, E, S, and SW flanks of the dome were sometimes generated from the lava-flow front and margins. Daily weak or weak-to-moderate explosions were recorded by the seismic network and on most days the explosions generated ash plumes that rose as high as 1 km above the complex and drifted mainly E, S, and SW. Weak rumbling was barely heard on nearby farms during 16-17 April. Residents were reminded to stay at least 6 km away from the 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)