Report on Santa Maria (Guatemala) — 23 July-29 July 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 23 July-29 July 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Santa Maria (Guatemala). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 23 July-29 July 2008. Smithsonian Institution and US Geological Survey.
14.757°N, 91.552°W; summit elev. 3745 m
All times are local (unless otherwise noted)
INSIVUMEH reported that on 22 July seismic stations monitoring Santa María's Santiaguito lava dome complex detected a lahar below the S flank in the Nima I river. Explosions observed on 23, 28, and 29 July from Caliente cone produced ash plumes that rose to altitudes of 2.8-3.3 km (9,200-10,800 ft) a.s.l. and drifted SW and W. Ashfall was reported in areas downwind. A lava flow and avalanches of blocks descended the SW flank. On 28 July, weak pyroclastic flows also traveled down the SW flank.
Geologic Background. Symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that 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 westward-younging vents, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.