On 6 November INSIVUMEH reported that activity at Santa María’s Santiaguito lava-dome complex transitioned from more extrusive to more explosive. The rate of lava effusion and advancement of the lava flows in the San Isidro and El Tambor drainages on the W and SW flanks had notably decreased. Explosivity had become more intense and audible in the recent weeks and particularly in the previous few days, according to seismic and infrasound data, webcam images, and reports from surrounding residents. Gas emissions had increased, and sulfur dioxide emissions were identified in satellite images during recent days. Gas, ash, and steam plumes rose as high as 500 m above the dome complex. Block avalanches from the dome, along with the ends and sides of the flows, descended the S, SW, and W flanks. Some block collapses generated ash clouds that rose to several hundred meters high. Lahars descended the Cabello de Ángel drainage (a tributary of Nimá I on the SE flank) on 3 November, carrying tree trunks, branches, and blocks up to 1 m in diameter. Minor ashfall was reported in Finca San José and La Quina on 5 November.

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)