Also known as San Gerónimo,[4] it is a monogenetic volcano like Negro de Chorrillos[5] and with it part of the geological Piedras Blancas Formation.[6] The volcano has a cone with three craters and reaches an elevation of 4,950 metres (16,240 ft), which covers an area of about 1.9 square kilometres (0.73 sq mi).[7] It developed on top of ignimbrites of Miocene age[1] of the Aguas Calientes caldera and is formed by lava, lava bombs and scoria.[8] The volcano erupted basaltic-trachyandesitic lava which propagated to distances of 8–10 kilometres (5.0–6.2 mi) from the vent[9] and which dammed a local river, forming a lake.[2] The dating of the eruption is uncertain; an older estimate was 780,000 ± 100,000 years ago but a newer indicates that it formed 144,000 ± 3,000 years ago. The older age was probably a product of rocks contaminated by xenoliths.[10]
San Jerónimo is part of a 170 kilometres (110 mi) long alignment of volcanoes along the Calama-Olacapato-El Toro fault. This string of volcanoes is diverse, including calderas and stratovolcanoes on the one hand and plutons and monogenetic volcanoes on the other hand.[11] This fault zone is represented by fault scarps, ponds and springs that occur in the area of the volcanoes.[2] One volcano that is part of this structure is Aguas Calientes caldera,[5] on whose border the San Jerónimo volcano is constructed.[1] The wider region is part of the Andean Central Volcanic Zone, where a number of volcanoes ranging from monogenetic volcanoes over polygenetic volcanoes to calderas developed.[12]
Petrinovic, I. A.; Riller, U.; Brod, J. A.; Alvarado, G.; Arnosio, M. (2006-04-15). "Bimodal volcanism in a tectonic transfer zone: Evidence for tectonically controlled magmatism in the southern Central Andes, NW Argentina". Journal of Volcanology and Geothermal Research. 152 (3–4): 240–252. Bibcode:2006JVGR..152..240P. doi:10.1016/j.jvolgeores.2005.10.008.
