Along the western edge of South America, the Andes Mountains encompass one of the largest concentrations of volcanoes on Earth. Many of these volcanoes are active, and in the historical record of just the past few centuries, eruptions have devastated villages, contaminated rivers and streams, and killed many people and animals. Today, active volcanoes threaten cities in the central Andes.

Thousands of years ago, people began moving into the Andes Mountains, developing technologies that allowed their societies to flourish in high and cold mountains. These mountains are a challenging place to live, where erratic weather, low oxygen levels, and short growing seasons can make life difficult. Besides volcanic eruptions, there are frequent large earthquakes, avalanches, floods and droughts. Despite these obstacles, the ancient people thrived, culminating in the Inca Empire, the last and greatest of the ancient Andean societies. The Incas built one of the most impressive empires in history, and the monuments they left behind, from Machu Picchu to Sacsayhuaman and many more, continue to be admired today.

Ancient Andean societies, along with many others worldwide, considered majestic, snow-covered mountains to be sacred. The Incas built shrines on the highest mountains, most notably on active volcanoes, as ceremonial places for offerings and occasionally for human sacrifices. Leaders made offerings to deities when volcanic eruptions or other natural hazards threatened societies—as well as when they celebrated a new ruler or important birth, commemorated a death, or sought successful harvests of crops. Those who selected mountaintop sites on active volcanoes for their rituals likely believed that angry gods controlled eruptions and that placating these deities was crucial.

Volcanoes in the Central Andes

The Andes Mountains extend for about 8,900 km (5,500 mi) along the western border of South America—they are the longest continental mountain range in the world. Located above a subduction zone where the Pacific plate is plunging beneath the South American plate, it is a highly active tectonic region within the Ring of Fire. Volcanologists estimate that over 100 Andean volcanoes have been erupting in the past 10,000 years or so, with another 100 volcanoes considered potentially active because of evidence of unrest, such as earthquake activity or gas discharge. The Andes also encompass the tallest volcanoes on land, including the two highest standing over 6,700 m (or about 22,000 ft), above sea level: Ojos del Salado and Llullaillaco, both active and on the northern border between Argentina and Chile.

Volcanic activity is occurring in four distinct zones. Named the Northern, Central, Southern, and Austral zones, wide gaps separate the areas with active volcanoes from those with none.

The Central Volcanic Zone extends from southern Peru into Bolivia, northern Chile, and Argentina. Within this zone are 44 major and 18 minor active volcanic centers. Presently, the level of activity within this zone is low, but since these volcanic centers have been active within the past 10,000 years, scientists consider them capable of erupting in the future. The Central Volcanic Zone overlies a segment of the subducting plate that is sloping down toward the mantle with approximately 25 to 30° dip. To the north is the Peruvian flat slab segment of the subduction zone, where active volcanoes are currently absent and earthquakes predominate.

The Global Volcanism Program of the Smithsonian Institution reports that during the Holocene, 13 volcanoes have erupted in Peru, 32 in Argentina, and 90 in Chile; in the centuries since 1800 CE, 46 volcanoes have erupted (5, 6, and 35, respectively for those countries). Within modern Peru, the birthplace of the Incas, several destructive eruptions have been recorded.

A devastating volcanic eruption took place in 1600 CE at Huaynaputina, about 80 km (50 mi) southeast of the modern city of Arequipa in southern Peru. Huaynaputina, or Waynaputina, means “young volcano” in Quechua, the language of the Incas. The 1600 explosion blanketed a vast region in volcanic ash up to 1.8 m (6 ft) deep, destroying entire villages and causing widespread destruction of settlements and crops. The Huaynaputina lahars of volcanic mud flowed downhill as far as 120 km (75 mi) to the Pacific Ocean, engulfing several villages within a broad swath along the route.

There are other active volcanoes near Arequipa, which has a population of around one million people. Ubinas volcano, about 72 km (45 mi) east of Arequipa, has erupted 23 times at low-to-moderate magnitudes in the past 500 years. From April 2006 through 2023, volcanic activity and lahars regularly damaged communities and required evacuations in the region around this volcano. Sabancaya volcano, about 64 km (40 mi) northwest of Arequipa, has a historical record with confirmed eruptions back to 1750. Increased activity in 1986 led to an explosive eruption in 1990. Most recently, Sabancaya has been in an eruption period since November 2016, with frequent gas and ash plumes and low-power thermal activity, along with earthquakes indicating rock fracturing events.

Perhaps the most potentially catastrophic volcano in Peru is Misti, a spectacular circular cone that soars to over 5,790 m (19,000 ft) only 16 km (10 mi) from Arequipa’s densely populated urban center. Vents releasing steam and volcanic gases have been active near the summit of the mountain within the past century. The last major eruption of Misti took place between about 2300 BCE and 2050 BCE, and there was a low-intensity eruption during Inca times, in the mid-1400s. Arequipa citizens have constructed city structures on the rocks of Misti lava flows that erupted only 2,000 years ago.

Shrines of the Incas

The Incas assembled their empire in less than one hundred years, using the foundation of thousands of years of ancient Andean traditions and technologies. Initially based in the Cuzco region, now in modern southern Peru, the Incas began incorporating adjoining territories around 1438 CE. By the time the Spanish conquistadors arrived in 1532 CE, the Inca Empire had expanded northwards to modern southern Columbia and southwards to the Bolivian highlands, northwest Argentina and central Chile. Along with fabulous monumental complexes and thousands of kilometers of stone-paved roads, the Incas constructed nearly 200 mountaintop shrines on Andean peaks over 5000 m (16,400 ft) in elevation.

No other society on Earth has constructed complex structures in extreme high-altitude environments. Aztec shrines are often on the slopes of volcanoes in Mexico, but at lower elevations and lacking the architectural complexities of their Andean counterparts. There are no mountaintop shrines in the Himalayas, where traditions can forbid ascents to the most sacred summits.

Artifacts from Inca shrines on mountaintops in southern Peru and northern Chile and Argentina provide hints about the ancient ceremonies conducted, including human sacrifices. There are no first-hand historical accounts of the high-altitude ceremonies from the Spanish Colonial period, and the Incas and their ancestors did not have a writing system that we recognize. However, one Spanish chronicler, Vasquez de Espinoza, describes the devastating 1600 CE Huaynaputina eruption in a text circa 1629. He reported that the indigenous peoples climbed to the top of the mountain and made human sacrifices in which the volcano would “swallow” the victims; the purpose presumably was to appease eruptions.

Interestingly, the locations of the Inca mountaintop shrines overlap the Central Volcanic Zone of the Andes, where ancient Andeans surely had views of active volcanoes releasing steam, ash, or molten lava. While we cannot know for sure why the Incas selected specific peaks for their shrines and sacrifices, the correlation of these sites with this volcanically active zone strikes me as not simply a coincidence.

Today we understand the science of volcanoes. Those who live in volcanic regions can receive warnings of eruptions in advance. That wasn’t the case for ancient Andeans. When a volcano burst into action, decimating communities and lives, people attempted to appease the angry gods they believed responsible for these violent disturbances. The Incas who built shrines on high peaks for offerings and sacrifices cast themselves as mediators between human society and deities.

Many mountaintop shrines have suffered damage after centuries of weathering from wind and water, lightning strikes, and looting by devious mountaineers. Nonetheless, researchers have recovered a variety of intriguing artifacts in the past few decades. On small stone platforms and in stone block enclosures, they have found an assortment of common objects such as llama bones, feathers, coca leaves, maize, pottery, and fiber cords. In some undisturbed shrines, archaeologists have found high-status goods of fine ceramics, exquisite textiles, Spondylus shells, feathered items, and elaborate gold and silver artifacts.

Most notable among the offerings from Inca mountaintop shrines are the frozen bodies of children and young women, sacrificed on the mountain peaks as part of important religious rituals. Officials selected boys and girls from throughout the empire for these roles because of their beauty, as only the best could be worthy to join the gods. Many were the children of elites and dignitaries. Having a child chosen for these important ceremonies reportedly brought great honor to a family, although it also must have brought great sadness. Pilgrimages were sometimes taken to reach a sacred site, with groups walking for months while accompanying the individuals to be sacrificed. The ritual sacrifices that took place on the slopes of the highest volcanic peaks in the Andes involved strenuous climbs for anyone, but especially for children. The mountaineering skills, as well as the faith of the Incas, were formidable.

On Aconcagua, the tallest peak outside of Asia with a summit elevation of 6,960 m (22,837 ft), mountaineers found the mummy of a young boy buried inside a stone structure at 5,303 m (17,400 ft). From the inner crater of Misti, near Arequipa, archaeologists excavated six Inca mummies, plus 47 statues and other artifacts.

On Llullaillaco, one of the highest active volcanoes on Earth, the Inca complex comprises several archaeological sites connected by a trail along the northeastern ridge of the mountain. Way stations, or tambos in Quechua, that presumably lodged the ceremony participants, were constructed at altitudes of 5,200 m (17,060 ft), 5,600 m (18,372 ft) and 6,300 m (20,669 ft). The ceremonial complex stood at an elevation of 6,739 m (22,110 ft). It contained the remains of nearly perfectly preserved frozen mummies of three children, with ages between about 4 and 13 years old, and over 100 splendid artifacts buried by Inca priests.

The Monumental Andes

The Incas and their ancestors faced environmental challenges ranging from volcanic eruptions and earthquakes to changing climates. Over thousands of years, they domesticated plants and animals, built large and impressive ceremonial complexes, developed sophisticated agricultural methods, and created exquisite textiles, ceramics and art objects in gold and silver. Ancient Andean beliefs shaped responses to their dynamic environment in diverse and unique ways.

In my recently published book, The Monumental Andes – Geology, Geography, and Ancient Cultures in the Peruvian Andes (University of Utah Press, 2024), I explore many of the interconnections between the ancient Andeans and their environment.

Roseanne Chambers

SOURCES

Ceruti, Maria Constanza, 2018. “Inca mountaintop shrines and glaciers in the high Andes.” Journal of Glacial Archaeology, 3.1: 59 – 78.

De Silva, S. L., and P. W. Francis, 1990. “Potentially Active Volcanoes of Peru: Observations Using Landsat Thematic Mapper and Space Shuttle Imagery.” Bulletin of Volcanology 52, no. 4: 286 – 301.

Ramos, Victor A., and A. Aleman, 2000. “Tectonic Evolution of the Andes.” In Tectonic Evolution of South America, edited by Umberto G. Cordani, Edison J. Milani, Antonio Thomaz Filho, and Diogenes de Almeida Campos, 453-480. 31st International Geological Congress, Rio de Janeiro, 2000.

Reinhard, Johan, and Constanza Ceruti, 2005. “Sacred Mountains, Ceremonial Sites, and Human Sacrifice among the Incas.” Archaeoastronomy 19: 1 – 43.

Smithsonian Institution, Global Volcanism Program. https://volcano.si.edu/volcanolist_countries.cfm?country=Peru).

Socha, Dagmara M., Johan Reinhard, and Ruddy Chávez Perea, 2021. “Inca Human Sacrifices on Misti Volcano (Peru).” Latin American Antiquity 32, no. 1: 138 – 153.

Stern, Charles R., 2004. “Active Andean Volcanism: Its Geologic and Tectonic Setting,” Revista Geológica de Chile 31, no. 2: 161 – 206.

Vazquez de Espinosa, A. 1990 [1629?]. Compendio y descripción de las Indias Occidentales. Colección Crónicas de América. Historia 16, Madrid: Atlas, as cited by Ceruti, 2018, p. 68.

Photo credits

Llullaillaco volcano (elev 6,739 m/22,110 ft); the last explosive eruption of the volcano occurred in 1877, by ISS Expedition 22 crew, 2010. https://commons.wikimedia.org/wiki/File:Llullaillaco_Volcano_in_Salta_province,_Argentina.jpg

Misti volcano above Arequipa, Peru, by Cristian123gme, 2020. https://commons.wikimedia.org/wiki/File:Volc%C3%A1n_Misti_sobre_Arequipa.jpg

Shrines on the secondary summit of Llullaillaco, border of Argentina and Chile, by Christian Vitri, 2012. https://commons.wikimedia.org/wiki/File:Chozas_dobles.jpg

Mummy of a young woman discovered on Llullaillaco, by grooverpedro, 2012 https://commons.wikimedia.org/wiki/File:Llullaillaco_mummies_in_Salta_city,_Argentina.jpg

Small sculpture found with the Llullaillaco mummies, by jimmyharris, 2009. https://commons.wikimedia.org/wiki/File:Ajuar_02.jpg

From All of Us at Volcanocafe to All of You: Happy Christmas and a Volcanicious 2026!

The traditional Christmas optical illusions!

How many circles can you see on the image below?

Can you find the parallel lines in the image below?

How many zig-zags are there in the image below?

And finally, A Christmas volcano quiz! (Note: this will take you to an external site)

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