Cerro Quemado, Guatemala: the volcanic history and hazards of an exogenous volcanic dome complex
Cerro Quemado is a Holocene, andesitic to dacitic, exogenous dome complex located in a back-arc volcanic field 5 km west of Quezaltenango, Guatemala. Activity in the back-arc Almolonga volcanic field began prior to 84,000 yr B.P. with growth and collapse of an andesitic stratovolcano and has continued to the present with sporadic eruption of silicic domes and flows. The Cerro Quemado dome complex covers about 12 km2, has a volume of nearly 2 km3, and comprises at least 8 vents. Historic activity is limited to extrusion of a blocky lava flow during a six-month period beginning in January 1818. Cerro Quemado lavas are biotite-bearing hornblende andesite and dacite. The calc-alkaline lavas have a disequilibrium mineral assemblage that includes: three populations of zoned plagioclase phenocrysts and microphenocrysts, hornblende, biotite, magnetite, two pyroxenes, olivine, and quartz. In addition, spherical inclusions (2 mm to 30 cm) of basaltic andesite (SiO2 56 wt. %) are ubiquitous in Cerro Quemado lavas. this petrographic evidence points to an origin by mixing of felsic and mafic magma for Cerro Quemado.
In the past, Cerro Quemado typically erupted viscous blocky lava flows (up to 120 m thick and 2.5 km long) and plug domes. The presence of tephra and pyroclastic flow deposits, however, indicates that explosive volcanism has also occurred at the dome. About 1150 yr B.P., the west flank of the dome gravitationally collapsed, producing a debris avalanche that underlies 13 km2of the Llano del Pinal valley, and avalanche caldera, 1 km × 1.5 km × 90 m deep. The caldera and avalanche deposit have identical volumes of approximately 0.1 km3. The collapse apparently precipitated a hot, laterally directed blast that swept about 40 km2 of rugged terrain that includes Llano del Pinal valley and the east slopes of nearby Siete Orejas to an elevation of 3100 m. A pyroclastic flow overlying the fines-poor lateral blast deposit apparently resulted from remobilization and flow age of hot blast deposits off the steep slopes of Siete Orejas. Subsequently, a small Peleéan dome was emplaced in the upper part of the avalanche caldera. Following the catastrophic events of 1150 yr B.P., Cerro Quemado was dormant until 1818 A.D.
Geologic mapping at Cerro Quemado volcano indicates that the principal volcanic hazards includes lava flow and exogenous dome growth, pyroclastic flow, debris avalanche, lateral blast, tephra fall, and mudflow. If Cerro Quemado erupts in the future Quezaltenango and environs (population more then 125,000) will be threatened.
Journal of Volcanology and Geothermal Research
Conway, F. Michael; Vallance, James W.; Rose, William I.; Johns, Glen W.; and Paniagua, Sergio, "Cerro Quemado, Guatemala: the volcanic history and hazards of an exogenous volcanic dome complex" (2003). Department of Geological and Mining Engineering and Sciences Publications. 103.