__NOTOC__ Acamarachi (also known as ''Pili'') is a high

volcano A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most oft ...

in northern

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

. In this part of Chile, it is the highest volcano. Its name means "black moon". It is a volcano in the Central Volcanic Zone of the

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

, a zone of strong volcanic activity during the last million years. Old volcanoes in the area are well-preserved, due to the dry climate. Acamarachi itself is a cone-shaped volcano with steep upper flanks and a lava dome on its northern side. While there is no indication of historical activity and the flank lava flows are old, some lava flows around the summit crater and a lava coulee north of Acamarachi on the

saddle A saddle is a supportive structure for a rider of an animal, fastened to an animal's back by a girth. The most common type is equestrian. However, specialized saddles have been created for oxen, camels and other animals. It is not know ...

between Acamarachi and Colachi volcano may be postglacial in age. Acamarachi is formed by andesitic and dacitic rocks. Acamarachi features an

Inca The Inca Empire, officially known as the Realm of the Four Parts (, ), was the largest empire in pre-Columbian America. The administrative, political, and military center of the empire was in the city of Cusco. The History of the Incas, Inca ...

mountain sanctuary on which several

figurine A figurine (a diminutive form of the word ''figure'') or statuette is a small, three-dimensional sculpture that represents a human, deity or animal, or, in practice, a pair or small group of them. Figurines have been made in many media, with cla ...

s have been found. One female figurine is made out of

silver Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...

, a male one is made out of thorny oyster. Both of these figurines were found with miniature clothing.

Geological context

The volcano is located in the Central Volcanic Zone, an area of volcanism in the Andes. Volcanism in this area is dependent on the

subduction Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...

in the Peru-Chile Trench. 27 million years ago, in this area of the Andes large rhyolitic eruptions commenced and formed major

ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surrou ...

s, dramatically increasing 10 million years ago. At the same time starting in the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

, andesitic to dacitic eruptive activity has formed large

stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...

es. This activity in the late

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

and

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

has created the current

volcanic arc A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc ...

. The climate of the area is hyperarid. Thus, ignimbrites and individual volcanoes keep most of their original appearance. Most of these volcanoes are remote structures that are unlikely to affect significant population, although wind-driven transport of

tephra Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...

can potentially cause economic and other damage at considerable distance.

Geology

Acamarachi is a high steep-sided conical volcano, like several other volcanoes in the region. Such a shape is due to the relatively high viscosity of the lavas forming them. In the case of Acamarachi, the upper slopes reach a slope angle of 45°. On the volcano's northern flank there is a large lava dome while the rest of the edifice is symmetrical. A deep crater lake lies in the summit crater and may be kept ice-free by magmatic heat. , it is considered the world's highest site of an underwater dive. Acamarachi is constructed by andesite and dacite. Rocks are porphyritic and contain

hornblende Hornblende is a complex silicate minerals#Inosilicates, inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common ...

as well as biotite or

pyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...

. Augite, hypersthene and

plagioclase Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continu ...

are also present, with smaller contents of

olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

and

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

. The composition of Acamarachi's rocks resembles that of Colachi's. A study of lava flows at the summit concluded that Acamarachi's last eruption may have occurred during the

. There are no young

lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

s on the flanks and the summit crater is degraded. Possibly after the

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...

s, north of Acamarachi a silicic coulee was erupted on the saddle between Acamarachi and Colachi. This coulee has well preserved flow structures and covers . No evidence exists for activity in historical times and the lack of volcanic damage to archeological sites suggests that it was active during the last millennium. Renewed activity would most likely generate lava flows or lava domes; impact would be limited on the immediate surroundings of the volcano. The volcano is part of a northwest-bound alignment along with Rili, Colachi and Yalquis-Putas, which may be linked to faults underground. However, Colachi and Acamarachi seem to have separate magmatic systems. They are both relatively low over the surrounding terrain which is about high and is formed by raised ignimbrites. Acamarachi does not have

glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

s or any perennial ice structures. Such lack of glaciation is also observed on other mountains in the neighbourhood such as Aucanquilcha and is probably due to the arid climate. In the past however the mountain was probably extensively glaciated, with glacier lobes forming at its foot and

cirque A (; from the Latin word ) is an amphitheatre-like valley formed by Glacier#Erosion, glacial erosion. Alternative names for this landform are corrie (from , meaning a pot or cauldron) and ; ). A cirque may also be a similarly shaped landform a ...

s developing around the summit.

Terminal moraine A terminal moraine, also called an end moraine, is a type of moraine that forms at the terminal (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, has been pushed by the front e ...

s lie in the Quebrada Ojos de Hécar and Quebrada Acamarachi, with several individual moraines between elevation.

Archeology

Acamarachi is known as an Inca mountain sanctuary, among at a minimum 15 other mountain sanctuaries known to have been used by the Inca. Other known sanctuaries are Cerro Colorado, Cerro Lailay, Cerro del Leon, Cerro Mullay, Cerro Toco, Cerro Quimal, Curiquinca, Juriques, Laguna Verde, Licancabur, Linzor, Paniri, Sairecabur, Tatio and Toconce. On its summit, four different ceremonial platforms are arranged in a cloverleaf conformation.

figurines representing individuals of various sexes have been found on Acamarachi. The figurines found at Acamarachi may represent mid-level imperial officials, considering the simple

tunic A tunic is a garment for the torso, usually simple in style, reaching from the shoulders to a length somewhere between the hips and the ankles. It might have arm-sleeves, either short or full-length. Most forms have no fastenings. The name deri ...

s they wore. One figurine made out of '' Spondylus'' shell wore miniature clothing made out of

camelid Camelids are members of the biological family (biology), family Camelidae, the only currently living family in the suborder Tylopoda. The seven extant taxon, extant members of this group are: dromedary, dromedary camels, Bactrian camels, wild Bac ...

wool Wool is the textile fiber obtained from sheep and other mammals, especially goats, rabbits, and camelids. The term may also refer to inorganic materials, such as mineral wool and glass wool, that have some properties similar to animal w ...

, the clothing having an imperial design with multicoloured decorations. The tunic itself is yellow. The textiles found on Acamarachi belong to a style known as "Catarpe", which is associated with Inca presence. Such clothing seems to be miniaturized versions of Inca clothing. This figurine has no plaque, unlike some other Inca figurines. A feather and a shawl are other accessories that have been found on the figurine. The function of such figurines is unknown, several theories have been proposed, such as representing deities. Another figurine representing a woman was also found there in 1971, in red miniature clothing with decorations too, as well as a red feather. This figure is made out of silver. Such dressed figurines have been found on other Andean summits, such as

Aconcagua Aconcagua () is a mountain in the Principal Cordillera of the Andes mountain range, in Mendoza Province, Argentina. It is the highest mountain in the Americas, the highest outside Asia, and the highest in both the Western Hemisphere and the ...

, Cerro El Plomo, Cerro Mercedario, Cerro Las Tortolas, Cerro Gallan, Copiapo and Pichu Pichu. Acamarachi's figurines are now exposed in the R. P. Gustavo Le Paige Archaeological Museum of San Pedro de Atacama. The region in which Acamarachi is located was a southern part of the

Inca Empire The Inca Empire, officially known as the Realm of the Four Parts (, ), was the largest empire in pre-Columbian America. The administrative, political, and military center of the empire was in the city of Cusco. The History of the Incas, Inca ...

Geological context

Geology

Archeology

See also

Notes

References

Sources

Further reading