The caldera is in a transitional region between thick and thin lithosphere, and is probably supplied by a pool of andesitic and rhyolitic magma.

This range includes at least nine caldera complexes, more than 70 of Chile's stratovolcanoes and volcanic fields that have been active in the Quaternary, and hundreds of minor eruptive centers.

The largest, which is on the southern rim of the caldera, is the Holocene Cerro del Medio complex with an elevation of 3,508 metres (11,509 ft).

On the southwestern edge several eruptions have created the Descabezado Chico volcano (elevation: 3,250 metres (10,663 ft))[1] which consists of four overlapping volcanic craters.

[1] Towards the center of the caldera, hot springs including Cajon Los Calabozos and Baños de Llolli[1] are present.

[2] The springs are as old as 0.3 mya, and may have formed directly after Calabozos's second eruption as a result of uplift caused by re-occurring activity in the caldera.

[7][2] The vents occur in two clusters, Colorado and Puesto Calabozos, and are located along the margin of a fault at the southwestern edge of the caldera.

[7] Hildreth et al. (1983) evaluated that Calabozos could potentially be useful for the harvesting of geothermal energy,[8] and exploratory holes have been drilled.

[2] Through K-Ar dating, geologist Robert Edward Drake established the age of 66 events in central Chile, and divided them into groups based on the time of their origin.

[12] Calabozos lies in an area between thick and thin continental crust, and its eruptions are probably fed from a pool of andesitic and rhyolitic magma that sits just under its caldera.

[14] Under its northeast edge, Calabozos is cut by a north–south trending segment of sedimentary rock that includes gypsiferous and carbonates.

[4] Calabozos is similar in age to Cerro Azul and Descabezado Grande, and its eruptions may correspond to past activity at both volcanoes.

The directional formation of this belt corresponds to the fold-and-thrust movement of the nearby Malargüe fault, which formed in the Tertiary and remained active until the early Pliocene or late Miocene.

[15] In comparison to the well-preserved rocks of the dry, central part of the Andes, the record that defines the southern sector is poorly preserved.

By examining the eruption rate of individual volcanoes, Hildreth et al. concluded that similar amounts of ash-flow volcanism took place in the southern sector as well.

Their study established that in particular silicic ash was missing from the record, and concluded that erosion had probably disrupted deposition of volcaniclastic rock.

[3] While the volcanic history of the area extends back far further, the earliest fully recognizable events in the region are recorded in the pyroclastic Campanario Formation.

Nearby volcanoes sit on top of two mya lavas that formed during this period, while the Loma Seca Tuff lies atop andesitic deposits from Descabezado Grande.

Temperature is also variable, typically registering 25 degrees Celsius during the summer, but dropping below freezing at high elevations (above 2,500 metres (8,200 ft)).

However, except for these basal layers and thin zones where the ash was devitrified (loses the properties of a glass and becomes brittle), the entire sheet is melded together.

Its extensive erosion can be explained by the presence of hydrothermal vents, and its high levels of lithics probably originate from either being exposed to the rocks after they were erupted, lying adjacent to them while they underwent subsidence, or is a result of long, slow formation.

Another zone of nonwelded material, about 20 metres (66 ft) and near Cajon Los Calabozos, underwent no erosion, suggesting that activity stopped, then began again.

[19] Calabozos is in the South Volcanic Zone, which contains potentially deadly and active volcanoes such as Mount Hudson, Llaima, and Villarrica.