Purupuruni is a group of

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 ...

s in southern

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...

and a correlative geological

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

. They are among the many volcanoes that exist in Peru and whose activity has been associated with the

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

of 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 ...

beneath the

South America Plate The South American Plate is a major tectonic plate which includes the continent of South America as well as a sizable region of the Atlantic Ocean seabed extending eastward to the African Plate, with which it forms the southern part of the Mid-A ...

. Purupuruni is associated with a geothermal field and a

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

. Volcanic activity occurred during the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

53,000 ± 8,000 years ago but also during the

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

about 5,300 ± 1,100 years ago; today the volcano is considered to be a low hazard volcano but is being monitored nevertheless.

Geography and geomorphology

Purupuruni lies in the Cordillera Occidental north of the border with

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

, about away from

Tacna Tacna was known for its mining industry; it had significant deposits of sodium nitrate and other resources. Its economic prosperity attracted a wave of immigrants from Italy. Today, their Italian Peruvian descendants live in the city and many of t ...

and only about from the town of Tarata. The volcano is part of the

geopark A geopark is a protected area with internationally significant geology within which sustainable development is sought and which includes tourism, conservation, education and research concerning not just geology but other relevant sciences. In 20 ...

. The term means dung in

Aymara Aymara may refer to: Languages and people * Aymaran languages, the second most widespread Andean language ** Aymara language, the main language within that family ** Central Aymara, the other surviving branch of the Aymara(n) family, which today ...

. The Purupuruni volcano, also known as Purupurini, is a wide complex of four large

s at an elevation of or . The domes cover an area of about , are up to high and are isolated and little eroded. The domes are accompanied by intrusions and

lava 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 un ...

and

pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of bu ...

deposits. The volcanism appears to come from

fissure vent A fissure vent, also known as a volcanic fissure, eruption fissure or simply a fissure, is a linear volcanic vent through which lava erupts, usually without any explosive eruption, explosive activity. The vent is often a few metres wide an ...

s and the volcanoes have been affected by faulting. These deposits reach thicknesses of and also occur on neighbouring volcanic centres. Purupuruni has formed on the rim of a depression, which is surrounded by eroded

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

volcanoes and appears to be a wide

southwest of the domes. The volcano lies east-southeast from

Yucamane Yucamane, Yucamani or Yucumane is an andesitic stratovolcano in the Tacna Region of southern Peru. It is part of the Peruvian segment of the Central Volcanic Zone, one of the three volcanic belts of the Andes generated by the subduction of the ...

volcano and just south of the

Mauri River The Mauri River is a river of Bolivia and Peru. It rises on the frontier between Chile and Bolivia near Charaña and flows east-northeast for about 100 km where it joins the Desaguadero. In fact the Mauri is much larger than the Desaguadero ...

; the Mauri River is part of the

Lake Titicaca Lake Titicaca (; es, Lago Titicaca ; qu, Titiqaqa Qucha) is a large freshwater lake in the Andes mountains on the border of Bolivia and Peru. It is often called the highest navigable lake in the world. By volume of water and by surface area, ...

watershed. The Borateras geothermal field with about 40 separate manifestations is associated with Purupuruni and neighbouring volcanoes such as Coverane and Jaruma across the Mauri River and west from Purupuruni respectively. The Borateras field is used as a

spa A spa is a location where mineral-rich spring water (and sometimes seawater) is used to give medicinal baths. Spa towns or spa resorts (including hot springs resorts) typically offer various health treatments, which are also known as balneoth ...

at the Calachaca spa. The landscape is relatively dry and cold and thus vegetation is scarce.

Geology

The volcanic rocks are mainly

andesitic Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...

and

dacitic Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite ...

, and contain

amphibole Amphibole () is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is A ...

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 ...

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more prope ...

and

pyroxene 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) ...

and are among the most differentiated volcanics in the area. They are part of the wider "Purupurini Volcanics", which are named after Purupuruni and also form other volcanoes in the region.

Geological context

Rock formations in the region include the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...

Yura Group sediments, the Toquepala

intrusive rock Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form ''Igneous intrusion, intrusions'', such as batholiths, dike (geology), dikes, Sill (geology), sills, laccoliths, and volcanic necks.I ...

s, the 30-24 million years old Tacaza volcanic rocks, the 24-10 million years old Huaylillas volcanic rocks and the 10-3 million years old Barroso volcanic rocks; Purupuruni is considered to be part of this Barroso formation. Purupuruni and neighbouring volcanic centres have formed on the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

sedimentary basement. Volcanism in Peru occurs mainly in the southern part of the country, where there are about 300 separate volcanic systems including

El Misti Misti, also known as Putina or Guagua Putina, is a stratovolcano of andesite, dacite, and rhyolite located in southern Peru near the city of Arequipa. With its seasonally snow-capped, symmetrical cone, Misti stands at above sea level and lies betw ...

Ubinas Ubinas is an active stratovolcano in the Moquegua Region of southern Peru, approximately east of the city of Arequipa. Part of the Central Volcanic Zone of the Andes, it rises above sea level. The volcano's summit is cut by a and caldera, wh ...

Ticsani Ticsani is a volcano in Peru northwest of Moquegua and consists of two volcanoes ("Old Ticsani" and "Modern Ticsani") that form a complex. "Old Ticsani" is a compound volcano that underwent a large collapse in the past and shed of mass down the ...

Sabancaya Sabancaya is an active stratovolcano in the Andes of southern Peru, about northwest of Arequipa. It is considered part of the Central Volcanic Zone of the Andes, one of the three distinct volcanic belts of the Andes. The Central Volcanic Zone i ...

and

Huaynaputina Huaynaputina ( ; ) is a volcano in a volcanic high plateau in southern Peru. Lying in the Central Volcanic Zone of the Andes, it was formed by the subduction of the oceanic Nazca Plate under the continental South American Plate. Huaynaputina ...

. In the

Tacna Region Tacna (; Aymara & Quechua: Taqna) is the southernmost department and region in Peru. The Chilean Army occupied the present-day Tacna Department during the War of the Pacific from 1885 to 1929 when it was reincorporated into Peruvian soil. Geogr ...

of Peru alone there are over 60 separate volcanoes, two of which,

Tutupaca Tutupaca is a volcano in the region of Tacna in Peru. It is part of the Peruvian segment of the Central Volcanic Zone, one of several volcanic belts in the Andes. Tutupaca consists of three overlapping volcanoes formed by lava flows and lava dom ...

and Yucamane, have been active in historical time. In addition, there are a number of geothermal systems with temperatures of over which could be used to produce

geothermal energy Geothermal energy is the thermal energy in the Earth's crust which originates from the formation of the planet and from radioactive decay of materials in currently uncertain but possibly roughly equal proportions. The high temperature and pres ...

. Volcanic and geothermal activity in the region is a consequence of the

of the

beneath the

at a rate of about .

Geologic history

The volcanic centres in the area including Purupuruni are of

Miocene The Miocene ( ) is the first 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 means "less recen ...

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

age. Purupuruni formed during the last 100,000 years and appears to have developed between two

interglacial An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene in ...

s; fission-track dating on glasses from Purupuruni has yielded ages of 53,000 ± 8,000 years ago but more recent

surface exposure dating Surface exposure dating is a collection of geochronological techniques for estimating the length of time that a rock has been exposed at or near Earth's surface. Surface exposure dating is used to date glacial advances and retreats, erosion histo ...

has yielded an age of 5,300 ± 1,100 years before present on one of the southern domes. The volcano is considered to be a low-hazard system and in 2018 the Peruvian Geological Institute announced it would begin monitoring Purupuruni and nine other volcanoes. Earthquake swarms in 2020 and 2021 do not appear to have been caused by volcanism; they are instead linked to local fault activity.

Glacial A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betw ...

erosion took place on Purupuruni during the Pleistocene, leaving

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 on the domes although research published in 2019 has found that the domes have not been eroded by glaciers even though evidence of glaciation occurs in the wider area.

Alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...

, glacial and

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluviog ...

deposits occur in the region, with aeolian sediments consisting of

volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcano, volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used t ...

mantling the volcanic structures.

References

Sources

* * * * * * * * {{Andean volcanoes Mountains of Peru Mountains of Tacna Region Holocene volcanoes