Later, a number of volcanoes such as Ermitaño and Peñas Blancas were constructed on the ring fault around the caldera, and lava domes developed within its confines.
[1] The international road between Chile and Argentina passes south of the caldera complex;[3] the region is remote and often described as inimical to life.
[6] Since 23 million years ago the Central Volcanic Zone has given rise to compound volcanoes, calderas and stratovolcanoes, which are formed mainly by andesitic or dacitic rocks.
Ojos del Salado, a member of the Central Volcanic Zone,[7] is the second tallest mountain in the Andes and the highest active volcano in the world.
The caldera is set into a terrain formed by volcanic rocks of Miocene-Pliocene age, chiefly lava flows of andesitic-dacitic composition.
[10] The region coincides with a lineament of volcanoes which forms the southern margin of the volcanically active Central Andes; south of this margin the Nazca Plate subducts beneath the South America Plate at a shallow angle and Quaternary volcanism is absent.
Because of the aridity, even high mountains are not covered with glaciers; Llullaillaco volcano is the highest non-glaciated summit on Earth.
The ignimbrite consists of at least two units which are rich in pumice fragments and lithic components of predominantly volcanic origin.
At the closing of this stage, lava domes and associated pyroclastic flows were emplaced within the caldera[11] and across the Cordillera Claudio Gay.