Structure and Evolution
This edifice is the largest and highest volcanic construct in Peru. It rises from a base level at about 4,500 m to form an elongate ridge which consists of at least 6 cones distributed over a 20 x 12 km area. Its highest point (6,377 m) is located at the northwest extremity. The light blue area on the TM image (Figure 1.1; 1.2) , obscuring much of the edifice, is a large permanent ice cap occurring above 5,300 m on the northern flank and above 4,800 m on the southern flank and covering ~130 km2 . Only minor valley glaciers are discernible on the modern volcano, but large glacial valleys (GV) and lateral moraines attributable to the ~10,000 yr BP glacial regression are prominent on all sides up to 10 km from the volcano and below heights of 4,500 m.
No historic activity is known from Coropuna and the youngest apparent activity is expressed by several pristine lava flows (L), extending out several kilometers from the northeastern, southeastern, and western flanks of the edifice. These are Holocene; they occupy glacial valleys and overlie the 10,000 yr BP moraines, and their morphology and preservation suggests that they are young. This is consistent with the observations of Venturelli et al. (1978).
Coropuna is one of a chain of volcanoes extending WNW-ESE, from the inactive Nevado Solimana in the west to Sabancaya in the east. This trend is paralleled by a number of young faults which are prominent on satellite images (Figure 1.2). These are best developed on the SW flanks, where Holocene normal fault displacements of at least tens of meters are conspicuous in the displacement of older lavas and stream beds.
There are no reports of current activity from Coropuna. Because the summit craters are ice covered, it can be presumed that there are no thermal manifestations at present.
Coropuna exhibits all the hazard potential inherent in a major ice covered volcano. Eruption of the visible lava flows was probably accompanied by major mud flows, though evidence for this is not seen on the satellite images. As with several other Peruvian volcanoes, an important additional factor is the presence of exceptionally deep and steep canyons along which mudflows and lahars would be channeled. The topographic relief adjacent to Coropuna is amongst the most greatest in the world, with elevation differences of up to 4,000 m vertically in 15 km horizontally. Several quebradas (Jollpa, Llacllajo, Tuailqui, Tastane) drain the south flank of the volcano into the great canyon of the Rio Majes (M). The road head in this valley is at Capiza (1,400 m) 30 km from the volcano. Numerous small settlements are present between Capiza and the volcano, and along the floor of the canyon as far as the Pacific ocean. Camaná, an important town with a population of ~20,000 lies at the mouth of the canyon, and it and all the other low-lying settlements along the canyon may be at risk from mudflows. On its western flank, drainages from the volcano flow into the even larger Ocoña canyon (O), via the Rio Chichas. This canyon is less densely populated. The combination of the exceptional relief and the extent of its icefield suggest that Coropuna presents unusually severe mudflow hazard.
Coropuna has been better studied than most Peruvian volcanoes (Venturelli, et al., 1978; Weibel, et al.,1978; Frangipane, 1976). Available analyses show that its lavas are high-K andesites (Venturelli et al.,1978)
de Silva S.L., & Francis, P.W., 1990. Potentially active volcanoes of southern Peru - observations using Landsat Thematic Mapper and Space Shuttle imagery. Bull. Volcanol. 52: 286-301.
Frangipane, M., 1976. Studio geochimico-petrografico del Nevado Coropuna (Peru meridionale). Unpub. PhD Thesis no. 5790 ETH, Zurich, Switzerland.
Thouret, J. C., Juvigne, E., Mariño, J., Moscol, M., Loutsch, I., Dávila, J., Legeley-Padovani, A., Lamadon, S., & Rivera, M., 2002. Late Pleistocene and Holocene tephro-stratigraphy and chronology in southern Perú. Sociedad Geológica del Perú, 93:45-61.
Venturelli, G., Frangipane, M., Weibel, M., & Antiga, D., 1978 Trace element distribution in the Cenozoic lavas of Nevado Coropuna and the Andagua Valley, Central Andes of Southern Peru. Bull. Volcanol. 41(3): 213-228.
Weibel, M., Frangipane-Gysel, M., Hunziker, J.C., 1978. Ein Beitrag zur Vulkanologie Süd Perus. Geol Rundsch. 67:243-252.