Peru
Synonyms: None
Location: 15º32'S; 72º19'W
Type: Lava field
Aerial Extent: 3600 m
Number of Centers: >25
The Andagua valley, known locally as the "valley of the volcanoes" is situated some 20 km to the ENE of Nevados de Coropuna in southern Peru. The valley is part of a large 60 km x 60 km scoria cone and lava field, where at least 25 discrete scoria cones of varying age can be recognized (Venturelli et al., 1976; de Silva & Francis, 1990). Many of these are old, probably pre-Holocene, since the lavas are degraded, and have high albedos, suggesting extensive weathering and partial aeolian cover (de Silva & Francis, 1989). The youngest lavas are those in the Andagua valley itself. The pristine morphology of the scoria cones and lavas suggest very young ages, perhaps as young as a few hundred years. Hoempler (1962, 1969) describes buildings as having been ruined by lava eruptions, but he does not give dates. Lavas from the vents in the valley floor have clearly dammed the valley of the Rio Andagua on several occasions. An existing small lake, Laguna de Chachas, appears to have been impounded by the youngest lavas, erupted from vents near Antaymarca. The most extensive of these is from Volcan Jenchana (15°32'S 72°19' W), extending a distance of approximately 10 km southwards down the Andagua valley as far as the intersection with the Rio Colca canyon; it may have temporarily impounded the Rio Colca itself (Figure M.16).
Geomorphologically, these structures are noteworthy because of the extremely steep slopes which some of the lavas descended, producing long, thin, ribbon-like flows. The development of the scoria cone field is related to the rift in which the Andagua valley has developed. In petrological terms, the lavas appear to be typical basaltic-andesites (Venturelli et al., 1978) with SiO2 ranging from 54.5 to 59.65%. Associated with the Andagua valley are the smaller fields of the Firura and Aiquihato complexes ~30km to the west-northwest (de Silva & Francis, 1990). Recent products of these complexes appear to be exclusively morphologically youthful basaltic andesite or andesitic lava flows which extend down into vegetated and settled areas around Chalahuerta.
References
de Silva, S.L., and Francis, P., 1990. Potentially active volcanoes of Perú - Obersvations using the Landsat Thematic Mapper and space shuttle photography. Bulletin of Volcanology, 52: 286-301.
Hoempler, A.L.O., 1962, Valle de Volcanes de Andahua, Arequipa. Andes Soc. Geol. del Peru 37, p59-69.
Hoempler, A.L.O., 1969, Valle de Volcanes de Andahua, Arequipa. Bol. Soc. Geog. Lima 88, p57-61.
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, p213-228.