Dartmouth College geologists visited Santa María in late November and early December. Ash eruptions, containing some incandescent material, occurred at intervals of 30 minutes or less from Caliente crater. The eruption clouds reached a maximum height of 1.5 km. Steam was emitted between ash eruptions. Considerable landsliding occurred from El Brujo Dome. The activity was comparable to that of July 1976, but there was less incandescence than in January 1976.

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: Dept. of Earth Sciences, Dartmouth College.