Incapillo is a Pleistocene-age caldera (a depression formed by the collapse of a volcano) in the La Rioja Province of Argentina.

The Incapillo ignimbrite was erupted 0.52 ± 0.03 and 0.51 ± 0.04 million years ago and has a volume of about 20.4 cubic kilometres (4.9 cu mi).

Later volcanism generated more lava domes within the caldera and a debris flow in the Sierra de Veladero.

Incapillo, located in Argentina's La Rioja province,[4] is the highest caldera stemming from explosive volcanism in the world.

[9] Incapillo is part of the Andean Central Volcanic Zone (CVZ), which extends through the countries of Chile, Bolivia, and Argentina and includes six or more Quaternary caldera or ignimbrite systems, about 44 stratovolcanoes, and over 18 smaller centres.

[16] There is an eastern group of lava domes between Monte Pissis and Cerro Bonete Chico, and a western one on the Sierra de Veladero.

[20] The Laguna Corona del Inca, considered to be the highest navigable lake in the world,[21] lies next to a heavily altered lava dome in the centre of the caldera.

Water temperatures of 13 °C (55 °F) obtained by satellite measurements suggest that hydrothermal activity persists in the lake.

[10] The Maricunga Belt, about 50 kilometres (31 mi) west of Incapillo, is where volcanism started 27 million years ago.

Wood, G. McLaughlin and P. Francis in a 1987 paper at the American Geophysical Union instead suggested a subdivision into nine different groups.

[5] Several studies indicate that trends in the isotope ratios of Incapillo's volcanic rocks are because of a thickening crust and increased contribution thereof to the magmas.

This shallowing forms the limit between the volcanically active CVZ and the magmatically inactive Pampean flat slab region farther south.

[4] Incapillo is part of a volcanic system active between 3.5 and 2 million years ago that includes Ojos del Salado and Nevado Tres Cruces.

[34] Isotope and composition data suggest that the magma of Incapillo formed at relatively constrained depths of approximately 65–70 kilometres (40–43 mi) above the shallow slab.

Typical pumice contains crystals of biotite, hornblende, plagioclase, quartz, and sanidine, with minor amounts of apatite, iron oxides, and titanite.

The changes in rare-earth element patterns occurred at the same time as the arc migrated eastward, terminating activity in the Maricunga Belt.

[42] The composition of the lava domes suggests that they were formed by degassed magma left behind by the caldera-forming eruption.

[34] The lead isotope ratios indicate that the volcano formed at the edge of an area of granite and rhyolite of Paleozoic age.

Grasses at 5,000 metres (16,000 ft) include Festuca, Stipa and in wetter areas also genera like Calamagrostis.

[23] Activity at Incapillo commenced shortly after the end of the Maricunga Belt volcanism and occurred first at Monte Pissis between 6.5 and 3.5 million years ago (mya).

[14] The ignimbrite appears in an eastward-heading ephemeral river valley and the southern Quebrada del Veladero, and possibly also next to the Rio Salado headwaters.

[15] The ignimbrite displays banding features away from the caldera and in Quebrada de Veladero football-sized clasts are mixed within fine ash.

[53] These lithics are derived from Sierra de Veladero, Cerro Bonete Chico, and Pircas Negras lavas.

It has a massive ungraded composition and is likely a lahar or debris flow deposit, probably influenced by glacial or crater lake water.

The elevated temperatures of the caldera lake suggest that hydrothermal activity still occurs beneath Incapillo.