Report on Santa Maria (Guatemala) — December 1991
Bulletin of the Global Volcanism Network, vol. 16, no. 12 (December 1991)
Managing Editor: Lindsay McClelland.
Santa Maria (Guatemala) Strong gas emission, frequent explosions, and block avalanches from lava dome
Please cite this report as:
Global Volcanism Program, 1991. Report on Santa Maria (Guatemala). In: McClelland, L (ed.), Bulletin of the Global Volcanism Network, 16:12. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN199112-342030.
14.757°N, 91.552°W; summit elev. 3745 m
All times are local (unless otherwise noted)
During 3 hours of observation following a pre-dawn ascent of Santa María on 4 January, the dome was continuously active, dominantly on its ESE side at Caliente vent. Copious steam emission was continuous from many fumaroles on the E half of the dome, with concentrated emission accompanied by subdued, pulsating roaring from a 25-m-diameter crater at Caliente's summit.
Episodic violent phreatic explosions occurred at intervals of 7-25 minutes, ejecting billowing, cauliflower-shaped steam clouds to heights ranging from 800 to 2500 m above the dome. There was no relationship between repose intervals and the size of subsequent explosions. Each explosion was heralded by a loud roar, lasting 2-4 minutes, from steam jets on the floor or rim of Caliente. Small blocks were commonly ejected onto the E flank of the dome during the early phases of each explosion. Minor ash from dissipating clouds generally drifted SE, lightly dusting vegetation.
Sporadic spalling of large blocks (estimated <=2 m in size) from the dome's E and S flanks indicated that the Caliente lobe was growing by intrusion. One small avalanche of rubble produced an apparent small pyroclastic surge that reached the S foot of the dome. Seared vegetation to several hundred meters SE of the dome suggested that larger pyroclastic surges had recently occurred.
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 3772-m-high stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 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.
Information Contacts: J.P. Lockwood, USGS; Sección de Vulcanología, INSIVUMEH.