INSIVUMEH reported that the Santa Maria-Santiaguito lava dome complex remained highly active during 29 March-4 April. Seismic stations and webcams recorded weak-to-moderate explosions which produced ash plumes to 4.3 km altitude (14,100 ft a.s.l.). Incandescence from the dome and along lava flow margins was visible most nights or early mornings. Weak-to-moderate block-and-ash flows were recorded around the crater, on the S, W, SE, SW, and E flanks, and at the front of the western lava flow. Ash plumes rose 3.5 km above the crater and drifted W on 31 March. Avalanches traveled down the S, SW, E, and N flanks; on 31 March the avalanches were accompanied by small pyroclastic flows. The active lava flow measured 4.3 km long in the WSW direction down the San Isidro and Zanión Seco drainages on 1 April, with some block collapses that generated ash clouds several hundred meters high. On 4 April ash plumes rose 3.5 km above the crater and drifted W and the active lava flow generated avalanches and moderate-to-strong pyroclastic flows.

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 W 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)