Paniri ( Aymara for "he who comes, visits") is a

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

located in El Loa Province, Antofagasta Region, Chile, and near the border with

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

. To its northwest lie the twin volcanoes San Pedro and San Pablo, and to its southeast lies Cerro del León, from which it is separated by the huge '' Chao''

lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on ...

. The volcano features lava flows, which are well preserved on the south-southwest flanks, and a

scoria cone Scoria is a pyroclastic, highly vesicular, dark-colored volcanic rock that was ejected from a volcano as a molten blob and cooled in the air to form discrete grains or clasts.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005) ''G ...

on its summit. The volcano has three

craters Crater may refer to: Landforms * Impact crater, a depression caused by two celestial bodies impacting each other, such as a meteorite hitting a planet * Explosion crater, a hole formed in the ground produced by an explosion near or below the surf ...

. Paniri also shows evidence of glacier activity on its southeastern slope. The volcano developed in several different stages with substages; the first stage formed a shield like volcano with most of its volume, the later ones formed the cone and "main edifice". One date obtained from the youngest stage is 150,000 years ago, with an uncertainty of 6,000 years. Once considered of Holocene or Pleistocene age, Paniri was later determined that to be of Pleistocene age. Paniri is part of the San Pedro-Linzor volcanic chain, a chain of volcanoes formed by

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 moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...

s and pyroclastic flows. Composition of the rocks erupted by Paniri ranges from basaltic andesite and dacite.

Geography and geomorphology

Paniri lies in the

Antofagasta Province Antofagasta Province ( es, Provincia de Antofagasta) is one of three provinces in the northern Chilean region of Antofagasta (II). The capital is the port city of Antofagasta. Located within the Atacama Desert, it borders the El Loa and Tocopil ...

of Chile.Hegna and Lazo-Wasem 2010, p.446 The volcano rises between Cerro Carcanal in the west and Cerro del Leon in the east. Roads lead around the northern and western flanks of the volcano.Godoy ''et al.'' 2018, p.188 The large lava flow Cerro Chao borders Paniri to the southeast and separates it from Cerro del Leon. The towns of Cupo and Turi lie west-southwest and south-southwest of Paniri, respectively. Paniri is part of the

Central Volcanic Zone The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South Americ ...

, a volcanic belt in the Andes. Other than Paniri, other volcanoes in the Central Volcanic Zone are Lascar, Sabancaya and Ubinas, as well as geothermal fields such as

El Tatio El Tatio is a geothermal field with many geysers located in the Andes Mountains of northern Chile at above mean sea level. It is the third-largest geyser field in the world and the largest in the Southern Hemisphere. Various meanings have bee ...

.Godoy ''et al.'' 2018, p.185 The volcano is formed by about two units and contains three summit craters and one vent; one of the craters contains a crater lakeGodoy ''et al.'' 2018, p.187 with dimensions of . The volcano is topped off with a

. Thick

s extend from the summit and form the foot of Paniri. Gullies cut into its slopes and

moraine A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice shee ...

s have developed around its summit.

Geology

Since the Jurassic, the

Nazca Plate The Nazca Plate or Nasca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction, along the Peru–Chile Trench, of the Na ...

has been subducting beneath the western margin of South America. This subduction process is responsible for the volcanism in the

of the Andes, one of four volcanic arcs in the Andes. The volcano is mainly of Pleistocene age, but well preserved surface features indicate it may be still active. Other parts of the volcano have been subject to glacial erosion and hydrothermal alteration, and evaporite deposits have formed on its feet. The basement that Paniri is constructed on consists of both

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

- Miocene sediments of the San Pedro formation and ignimbrites of Miocene age which are formed by rhyodacitic and rhyolitic material. Atop this basement Paniri developed together with other volcanoes such as Cerro Chao in a linear volcanic chain, the San Pedro-Linzor complex which is formed by

lava flows Lava is molten or partially molten rock ( magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land o ...

and pyroclastic flows and whose existence may be due to a tectonic lineament. The chain is made up by San Pedro, San Pablo, Paniri, Cerro Chao, Cerro de Leon, Toconce and Linzor. Paniri has erupted rocks ranging from basaltic andesite to

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...

, which mainly define a potassium-rich calc-alkaline volcanic suite.Godoy ''et al.'' 2018, p.192 Phenocrysts include

biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more alumino ...

, clinopyroxene, hornblende, olivine, opaque minerals,

orthopyroxene The pyroxenes (commonly abbreviated to ''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 calcium (Ca), sodium (Na), iron (Fe II) ...

, plagioclase, quartz and rutile; the exact composition varies between various units. Alteration of the erupted rocks has given rise to clay,

chlorite The chlorite ion, or chlorine dioxide anion, is the halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as salts of chlorous ac ...

, epidote and illite. Magma genesis at Paniri appears to involve both the assimilation of crustal rocks in the Altiplano-Puna volcanic complex and

fractional crystallization Fractional crystallization may refer to: * Fractional crystallization (chemistry), a process to separate different solutes from a solution * Fractional crystallization (geology) Fractional crystallization, or crystal fractionation, is one of the ...

processes in shallow magma chambers.

Life and human history

The fairy shrimp ''

Branchinecta brushi ''Branchinecta brushi'' is a species of fairy shrimp found at an altitude of in the Chilean Andes. Distribution and discovery The type specimens of ''B. brushi'' were collected on December 13, 1988 by Charles F. Brush during an attempt to bre ...

'' was discovered in 2009 in the crater lake of Paniri. The occurrence of this shrimp at Paniri made it the highest finding of crustaceans known. Native people, considered to be Inka, made the first ascents of this mountain. Claudio Lucero and Nelson Muñoz made the first recorded ascent of Paniri in 1972. They found archaeological remains on its summit,Humberto Barrera, "Paniri", '' American Alpine Journal'', 1974, p. 194. Available a
AAJ Online
(PDF). which along with similar sanctuaries at Licancabur and other mountains are considered to be of Inka origin. Paniri is the sacred mountain for the village of Ayquina, and was also used as a source of dacitic rocks.

Eruptive history

The first units erupted by Paniri are the mainly lavic (plus one

pyroclastic Pyroclastic rocks (derived from the el, πῦρ, links=no, meaning fire; and , meaning broken) are clastic rocks composed of rock fragments produced and ejected by explosive volcanic eruptions. The individual rock fragments are known as pyroc ...

deposit) Malku unit which crops out in the northwestern sector of the volcano and the Los Gordos unit. The Los Gordos unit consists of pyroclastics and brecciated lava flows which are much thicker than these of the Malku unit; they crop out north and northwest of Paniri and one date obtained from this unit is 1.39 ± 0.28 million years ago. These two units define the "shield" stage of Paniri, the longest lasting and most voluminous phase of volcanic activity at this volcano.Godoy ''et al.'' 2018, p.196 Afterwards, the widespread Las Lenguas unit was emplaced which consists of blocky lava flows with some thin pyroclastic deposits. Ages of 640,000 ± 140,000 to 400,000 ± 100,000 have been obtained by radiometric dating. More restricted in exposure is the Las Negras unit, which forms basalt- andesite lava flows with prominent

levee A levee (), dike (American English), dyke (English in the Commonwealth of Nations, Commonwealth English), embankment, floodbank, or stop bank is a structure that is usually soil, earthen and that often runs parallel (geometry), parallel to ...

s on the northwestern flank of Paniri (one of these is dated to 402,000 ± 46,000 years ago). This is considered to be the "main edifice" stage of volcano growth at Paniri. The last three units of Paniri are the Viscachas, Laguna and Llareta units. The former consists of lava flows on the southeastern flank, with dates of 325,000 ± 8,000 and 300,000 ± 100,000 years before present. The Laguna unit again features lava flows but also breccia and

material, and one age of 169,000 ± 5,000 was obtained on its rocks. The last unit, Llareta, was erupted by the summit vent which generated lava flows on the northeastern and southwestern sectors of the volcano, plus large pyroclastic bombs. Its age ranges 264,000 ± 99,000 to 150,000 ± 6,000 years before present. These are considered to be the Old Cone and New Cone stages of volcano growth. The volcano was formerly considered to be of Holocene age. Electric conductivity anomalies imply that there is still a geothermal system under Paniri; a magma chamber may not be sufficiently visible.Mancini ''et al.'' 2019, p.4394

References

* * * *

External links

*
South American Summits Ranked By Re-Ascent
Chao dacite domes

{{DEFAULTSORT:Paniri Volcanoes of Antofagasta Region Mountains of Antofagasta Region Stratovolcanoes of Chile Five-thousanders of the Andes Pleistocene stratovolcanoes