On 27 August-2 September, INSIVUMEH reported lava flowing towards Upper Nima Canyon I at Santiaguito. On most days collapses of the lava flow generated fine ash that rose 300-2800 m above the crater and drifted SW, S, and W;ash was reported at Finca San José on 28 August. Fumarolic degassing plumes rose 150 -3,000 m above the crater and drifted SW, S, and E. On 30 August lahars left deposits about 1 m thick and 30 m wide, and on 1 September were reported to occasionally overflow in some parts of the Nima 1 river.

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)