The Guatemalan press reports that blocks and ash erupted from Santiaguito on 23 July dammed the headwaters of three S-flank rivers; the Nimá I and II and the Tambor, forming a large lake. The breakup of these temporary dams on 24 July produced mudflows that damaged farms and destroyed bridges, isolating some villages. Damage was estimated at about $1 million, but no casualties were reported. Ash emission was continuing on 28 July. Another mudflow, on 2 September, killed one person and caused further damage.

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.

Information Contacts: Diario El Gráfico, Guatemala.