INSIVUMEH reported that the eruption at Santa María’s Santiaguito lava-dome complex continued during 26 April-2 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 rose as high as 1 km above the dome and drifted W and SW. The explosions were also accompanied by block-and-ash flows that descended multiple flanks of the dome. Avalanches of material were also generated from the lava-flow front and margins. During 28-29 April quiet rumbling sounds were barely heard on nearby farms. Incandescence from the dome and the lava flows was visible nightly. On 28 April a lahar descended the Cabello de Angel River, a tributary of the Nimá I and Samalá rivers, on the E flank and was registered by the nearby seismic stations. The lahar consisted of volcanic material, water, volcanic blocks up to 1 m in diameter, and tree trunks and branches. On 30 April at 0920 a moderate explosion generated a pyroclastic flow that traveled 5 km SW and produced an ash cloud that rose 100 m along the flow. Seismic data confirmed that the event lasted 40 minutes.

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)