Above the subduction zone, the crust is chemically modified and generates large volumes of melts that form the local caldera systems of the APVC.

More recent activity occurred 1.7 mya and formed a smaller ignimbrite with a volume of 10 cubic kilometres (2.4 cu mi).

The resulting caldera formed like a trapdoor and with a volume of 1,200 cubic kilometres (290 cu mi) is among the largest known.

[9] Laudrum et al. suggested that the heat from Guacha and Pastos Grandes may be transferred to the El Tatio geothermal system to the west.

[2] Since the Jurassic, subduction has been occurring on the western margin of present-day South America, resulting in variable amounts of volcanic activity.

[5] Guacha caldera is part of the Altiplano-Puna volcanic complex (APVC), an igneous province in the central Andes covering a surface area of 70,000 square kilometres (27,000 sq mi).

Here on an average altitude of 4,000 metres (13,000 ft) between 10 and 1 mya roughly 10,000 cubic kilometres (2,400 cu mi) of ignimbrites were erupted.

Activity along this lineament commenced with the Abra Granada volcanic complex 10 mya ago and dramatically increased more than a million years later.

[16] The Guacha system was constructed over a timespan of 2 million years with a total volume of 3,400 cubic kilometres (820 cu mi).

Calculations indicate that the Guacha system was supplied by magmas at a rate of 0.007–0.018 cubic kilometres per year (5.3×10−5–0.000137 cu mi/Ms).

[12] Located at a high altitude in an area of long term arid climate has preserved old volcanic deposits over time.

[4] Thus, unlike in other areas of the world such as the Himalayas where water erosion governs the landscape the morphology of the Altiplano-Puna volcanic complex is mostly tectonic in origin.

The Chajnantor lava dome contains sanidine while Rio Guacha of dacitic composition contains amphibole and pyroxene.

The eastern mountain chain of the Andes prevents moisture from the Amazon from reaching the Altiplano area.

This is consistent with the climate of the Guacha region displaying long-term aridity for the last 10 mya as well as with the scarcity of pronounced geothermal systems in the APVC which are essentially limited to the El Tatio and Sol de Manana fields.

[20] Guacha has been the source of eruptions with volumes of more than 450 cubic kilometres (110 cu mi) dense rock equivalents.

One stream spreads 60 kilometres (37 mi) northwards past Uturunku volcano along the Quetena valley[6] until Suni K'ira.

[6] This ignimbrite ponded inside the Guacha caldera, and one particularly thick layer (>200 metres (660 ft)) is found beneath Zapaleri stratovolcano.

[7] The Puripica Chico ignimbrite is known for having formed the Piedras de Dali hoodoos, named like that by tourists because of their surreal landscape.

It has a volume of 10 cubic kilometres (2.4 cu mi) and it was apparently erupted at the hinge of the Guacha caldera.