Tocomar has generated several pyroclastic flows during the Pleistocene as well as phreatic-phreatomagmatic activity, and a magma chamber may still exist beneath the volcano.

Other than this, Tocomar was used as a source of obsidian in antiquity and more recently as a candidate site for a gamma ray observatory and as a mine.

[20] After being heated by the deep geothermal system, the water seems to interact with another shallower aquifer before emerging in the springs.

[40][16] The Tocomar volcano was constructed atop the ignimbrites from the Aguas Calientes caldera, as well as Pleistocene sediments which display traces of earthquake activity and form an alluvial cone.

[19] The oldest outcropping basement in the region is the Precambrian Puncoviscana Formation east of Tocomar, in the San Antonio de los Cobres ridge.

[45] The Tocomar centre has erupted rhyolitic ignimbrites, which belong to the potassium-rich peraluminous calc-alkaline magmatic series.

[12] The region is sunny,[46] dry, windy, cold and has a high difference between daytime and nighttime temperature.

[9] Among the animals of the area are camelids[46] such as the guanaco and the vicuña, rodents like the chinchilla and viscacha, the cervid taruca,[53] 20 species of birds[54] including the iconic flamingos[46] and the Andean toad Rhinella spinulosa, which lives in high altitude wetlands.

It consists of several different units of pyroclastic material,[41] which cover a surface of about 50 square kilometres (19 sq mi).

[58] A first eruptive episode was phreatomagmatic and generated a low eruption column which in turn gave rise to pyroclastic flows and pyroclastic surges, which were heavily influenced by the topography as they propagated and then came to rest, giving rise to several geological units[57] which are each 5–10 metres (16–33 ft) thick.

[59] At least three lapilli tuff units are present, the thickest of which has a massive structure and reaches a thickness of 3.5 metres (11 ft).

[58] The secondary unit is about 3–15 metres (9.8–49.2 ft) thick and consists of blocks embedded within a matrix formed by lapilli.

[12] This second eruption was phreatic and took place a while after the first one;[57] it was probably caused by the interaction of rhyolitic magma with the old geothermal system,[22] and triggered by movement along the local faults.

[63] Gravimetric anomalies, the presence of magmatic water in the springs and their high temperatures of about 80 °C (176 °F) indicate that a magma chamber still exists beneath Tocomar.