Based on a METAR weather notice, the Washington VAAC reported ash above Santa María's Santiaguito lava dome on 20 January. Satellite imagery showed a small plume drifting NNE at a possible altitude of 5.2 km (17,000 ft) a.s.l. During 20-21 January, INSIVUMEH reported that steam plumes rose 150 m above the crater and drifted SW. Avalanches originated from the lava dome SW of Caliente lava dome. On 21 January, the VAAC reported that an ash plume detected in satellite imagery drifted SW at an estimated altitude of 4.3 km (14,000 ft) a.s.l. They also noted that INSIVUMEH reported mostly steam plumes and rockfall-generated small ash plumes that drifted within 5 km of the crater. During 23-24 January fumarolic plumes rose 300 m above the crater and drifted N.

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.

Sources: Washington Volcanic Ash Advisory Center (VAAC), Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)