On 29 and 30 January, Maurice Krafft flew over Santiaguito. Explosions about once every 2 hours from Caliente Vent ejected gray, relatively ash-poor plumes. On 29 January at 1114, an eruption column rose to about 4.5 km altitude, 2 km above the vent, and another column reached about 3 km altitude the next day at 0946. No rockfalls were noted at the fronts of viscous block lava flows that had been active in previous years, and pilots reported that the flow fronts had also been quiet a few weeks earlier. High above the dome, frequent rockfalls occurred from the NE part of Santa María's crater, breached during the major eruption of 1902.

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: M. Krafft, Cernay, France.