The Volcanoes Valley

This is a spectacle which belongs to the prehistoric epochs when the planet was still in the throes of formation. This truly lunar landscape is located to the East and perpendicular to the Colca. The river Andagua runs through the Valley of the Volcanos, from north to south, to the east of the massive volcano of Coropuna, for a distance of 80 km. This valley is itself a deep open fault, which extends to the area of Huambo and which the Colca later cuts through perpendicularly. The floor of this open fault, which now appears like a valley, is filled with abundant flows of basaltic lava, spread in various layers.
Curiously enough the river runs underground for 17 km, covered by a lava flow, from Chachas Lake to Mamacocha Lake. The river of the same name as the latter is an important tributary to the Colca.
These lava flows originated in multiple eruptions of small volcanos (80 according to Hoempler) which burst up like bubbles rising from gasses given off by the lava itself, or as byproducts from other eruptions direct from the magmatic furnaces.
The highest of the volcanos of Andagua is Pucamauras, which rises 350 m above the valley floor. There are others from 50 to 70 m high, and smaller ones from 15 to 20 m, such as Chilcayoc.
These little volcanos of Andagua represent one of the most recent events in the geological history of the volcanic formations in the south of Peru. They date from the Quaternary, some 200 thousand years ago, to as recently as historical time.
The Valley of the Volcanos, which must be considered as a huge geological fault, has its continuity brusquely interrupted by the tectonic fault in which the Colca River flows in its descending course. Thus the floor of the valley on the Andagua side is between 500 and 800 m lower than the floor on the Huambo side. It is evident that this rise is due to the fault in this sector, and in a later phase, to the fault of the Valley of the Volcanos itself.
Geological data such as these give convincing evidence of the existence of breaks of great magnitude in the earth's crust, even to those observers who are unschooled in geology. These observations can be easily made from the village of Ayo (1,956 m; the river bed is at 1,405 m), which is situated at the end of the Valley of the Volcanos and almost on the Colca River.
Logically, the plain in the fault has suffered extensive erosion and now seems to be somewhat inclined and almost rounded. The difference in the elevations of the two sides of the river is evident, but the direction of the movement produced by the fault is not easy to establish, according to Doctor Alberto Parodi.
Strange flora flourish in the little spots free from lava and rich in volcanic ash. Cactus is the dominant vegetation, especially the giant saguaros and there are some isolated examples of Chachacoma and puma rosa, which are medicinal and widely used by the inhabitants of this region.
Small agricultural areas exist between the volcanos where potatoes, corn and wheat are cultivated, solely for the subsistence of the inhabitants.
The village of Andagua, at 3,600 m above sea level, was important during the colonial period. The mine of Orcopampa, 40 km from Andagua, still functions today.
The fauna is that characteristic of Andean tableland 3,800 m above sea level.