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Lastarria is a high
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 peri ...
that lies on the border between
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 eas ...
and
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the List of South American countries by area, second-largest ...
. It is remote and the surroundings are uninhabited but can be reached through an unpaved road. The volcano 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 America ...
, one of the four segments of the volcanic arc of the
Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
. Over a thousand volcanoes - of which about 50 are active - lie in this over long chain of volcanoes, which is generatedby
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, ...
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 N ...
beneath the
South American 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 ...
. The volcano is constituted by two volcanic edifices that form a ridge, and one subsidiary
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 un ...
field southwest of the main volcanoes. The main edifice features several aligned craters that form a line. There is no recorded eruptive activity, but the volcano displays vigorous
fumarolic A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volc ...
activity on its northern side and within the craters. It is located on top of older volcanic rocks and features both
andesite 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 predo ...
and
dacite 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 rhyo ...
. Lastarria produced a large
landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environmen ...
deposit when part of its southeastern flank collapsed. From a wide collapse scar, the landslide descended over a distance of . The intense fumarolic activity makes the volcano the largest source of volcanic gases in the region, and has produced fumarolic vent deposits as well as flows of molten
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
. A progressive uplift of the terrain around Lastarria and farther south has been recognized, it appears to reflect a deep magma intrusion in the region.


Geography and structure

Lastarria is situated in the Central Andes, in the
Antofagasta Region The Antofagasta Region ( es, Región de Antofagasta, ) is one of Chile's sixteen first-order administrative divisions. The second-largest region of Chile in area, it comprises three provinces, Antofagasta, El Loa and Tocopilla. It is bordered t ...
of
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 eas ...
, and straddles the border with
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the List of South American countries by area, second-largest ...
's
Salta Province Salta () is a province of Argentina, located in the northwest of the country. Neighboring provinces are from the east clockwise Formosa, Chaco, Santiago del Estero, Tucumán and Catamarca. It also surrounds Jujuy. To the north it borders Bolivi ...
. The city of
Antofagasta Antofagasta () is a port city in northern Chile, about north of Santiago. It is the capital of Antofagasta Province and Antofagasta Region. According to the 2015 census, the city has a population of 402,669. After the Spanish American wars ...
lies northwest of Lastarria. The Central Andes are difficult to access and its volcanoes are usually poorly monitored. There are no human populations within of Lastarria. From the former Catalina
railway station Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in Track (rail transport), tracks. In contrast to road transport, where the ...
west, an unpaved road leads to Lastarria. Unlike most other volcanoes in the region, no Inka
archeological site An archaeological site is a place (or group of physical sites) in which evidence of past activity is preserved (either prehistoric or historic or contemporary), and which has been, or may be, investigated using the discipline of archaeology an ...
has been found on Lastarria. Either the volcano was too active or too unimportant in
pre-Hispanic In the history of the Americas, the pre-Columbian era spans from the original settlement of North and South America in the Upper Paleolithic period through European colonization, which began with Christopher Columbus's voyage of 1492. Usually, ...
times. Lastarria is part of the Andean
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 America ...
, which extends over from
Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = National seal , national_motto = "Firm and Happy f ...
to Chile. Over 1,000 volcanic edifices have been identified in this zone, of which about 50 volcanoes are active or potentially active, with many exceeding in altitude. In addition, the zone features 18 monogenetic volcanoes and about 6
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 ...
/
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 surro ...
systems.


Edifice proper

Lastarria is formed by two coalesced edifices, the main cone and the older South Spur ('), which are joined at an altitude of about and form a long ridge. The main cone comprises
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 ...
s,
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 un ...
s,
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 b ...
s, and
scoria 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) '' ...
, and reaches a summit height of . Most of the volcano is covered by pyroclastic material, some of which extends to the southeastern margin of the . Lava flows are exposed mainly on the northwestern slope, where they reach thicknesses of . The South Spur has also generated lava flows. The volcano covers a surface area of about . Five overlapping
crater 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 ...
s are aligned in a north–south line on Lastarria's main cone, the craters 5-4 and 3-2 are nested within each other (counted from south to north). Volcanic activity has migrated north during the history of Lastarria, and the most recent eruption products are found on the northern and western slopes. A lava dome sits on the northernmost crater rim. The South Spur has two craters. The volcano rises from a terrain of about altitude and has fairly steep slopes. Much of the surface, including the Southern Spur, is covered by deposits left by
volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer ...
fall. Some parts of the Southern Spur display evidence of
hydrothermal alteration Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is the replacement of one rock by another of different mineralogical and chemical co ...
. The total volume of the edifice is about . The (also known as Big Joe) lava flow complex lies southwest of the Lastarria volcano and covers a large surface area. It is formed by several massive flows erupted from a single vent during three or eight pulses; the longest reaches a length of . These lavas are
block 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 und ...
s with flow ridges and levees. The total volume of the lava field is about and it is often grouped together with Lastarria and South Spur as the Lastarria Volcanic Complex. Neighbouring mountains include Chili volcano northeast, the high northwest and the high close to Negriales de Lastarria in the southwest. Almost due north of Lastarria lies the , a salt pan with a waterbody that is almost a lake, its name is a reference to the sulfur deposits of Lastarria. The fumarolic system may draw water from this waterbody. Water levels in the lake were higher in the past, as evidenced by two recognizable shorelines, which owing to tectonics related to recent volcanism in the
Corrida de Cori Corrida de Cori is a mountain range in Argentina and Chile. It consists of several aligned volcanoes, including Cerro Escorial, which exceed in elevation. The range, together with several local volcanoes, forms an alignment that may be control ...
crop out mainly on the eastern side, and the lake's surface area reached . There is a valley and a lake also at the southeastern foot of Lastarria.


Landslide scar

A major
sector collapse A sector collapse is the collapse of a portion of a volcano due to a phreatic eruption, an earthquake, or the intervention of new magma. Occurring on many volcanoes, sector collapses are generally one of the most hazardous volcanic events, and will ...
occurred on Lastarria's southeastern flank, leaving a clearly defined north–south
scarp Scarp may refer to: Landforms and geology * Cliff, a significant vertical, or near vertical, rock exposure * Escarpment, a steep slope or long rock that occurs from erosion or faulting and separates two relatively level areas of differing elevatio ...
in the volcano that opens to the east-southeast. The scarp reaches a maximum height of and forms a semicircle just under wide; the northern part is longer than the southern and the western part directly abuts the margin of the southernmost crater of Lastarria. The highest point of the scarp lies at an altitude of . The debris avalanche deposit is long and well preserved with landforms such as lobes, levees and hummocks. After exiting the collapse scar over its northern opening, it overrode an older
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) ...
before coming to rest. The slide, bordered by
levee A levee (), dike (American English), dyke (Commonwealth English), embankment, floodbank, or stop bank is a structure that is usually earthen and that often runs parallel to the course of a river in its floodplain or along low-lying coastli ...
-like structures reaching a height of , formed wide and high lobes. Unlike many debris avalanche deposits, the Lastarria debris avalanche lacks large blocks and has only a few hummocks. The velocity of the avalanche has been estimated to have been over , a fairly high velocity for a volcanic debris avalanche, while later research proposed a maximum speed of . It is possible that air was entrained in the debris, which thus assumed properties similar to an
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 surro ...
. The collapse occurred without any preceding instability of the edifice. The avalanche deposit consists mostly of loose material such as ash,
lapilli Lapilli is a size classification of tephra, which is material that falls out of the air during a volcanic eruption or during some meteorite impacts. ''Lapilli'' (singular: ''lapillus'') is Latin for "little stones". By definition lapilli range ...
,
pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular v ...
, with only a few lithic blocks. This loose consistency may explain the lack of megablocks. Its total volume is about , less than the volume of the Mount St. Helens and Socompa deposits. It is comparable to the volume of the landslide that the Ancash earthquake triggered on
Huascarán Huascarán () (Quechua: Waskaran), Nevado Huascarán or Mataraju is a mountain in the Peruvian province of Yungay ( Ancash Department), situated in the Cordillera Blanca range of the western Andes. The southern summit of Huascarán (Huascará ...
in
Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = National seal , national_motto = "Firm and Happy f ...
in 1970, resulting in more than 20,000 fatalities. Evidence points to previous flank collapses at Lastarria.


Internal structure

The internal structure of a volcano has been visualized with a technique known as
seismic wave A seismic wave is a wave of acoustic energy that travels through the Earth. It can result from an earthquake, volcanic eruption, magma movement, a large landslide, and a large man-made explosion that produces low-frequency acoustic ener ...
tomography Tomography is imaging by sections or sectioning that uses any kind of penetrating wave. The method is used in radiology, archaeology, biology, atmospheric science, geophysics, oceanography, plasma physics, materials science, astrophysics, ...
. An inverted funnel-shaped low velocity anomaly with a width of extends to a depth of beneath the volcano and appears to be associated with areas of high fumarolic activity; it may be the hydrothermal system. An even stronger anomaly at depths of may be the
magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it up ...
of the volcano and an associated fluid-filled system.
Magnetotelluric Magnetotellurics (MT) is an electromagnetic geophysical method for inferring the earth's subsurface electrical conductivity from measurements of natural geomagnetic and geoelectric field variation at the Earth's surface. Investigation depth ra ...
imaging showed structures similar to those revealed using seismic imaging.


Geology

Off the western coast of South America, 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 N ...
subducts 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 ...
at a rate of . Volcanism in the Andes occurs in four distinct regions: the
Northern 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 America ...
, 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 America ...
, the
Southern 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 America ...
, and the
Austral 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 America ...
. All but the last are geographically 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, ...
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 N ...
beneath the
South American 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 ...
; the Austral Volcanic Zone involves the subduction of the
Antarctic Plate The Antarctic Plate is a tectonic plate containing the continent of Antarctica, the Kerguelen Plateau, and some remote islands in the Southern Ocean and other surrounding oceans. After breakup from Gondwana (the southern part of the superconti ...
beneath the South American Plate. Magmatic processes important in the Central Andes include the
partial melting Partial melting occurs when only a portion of a solid is melted. For mixed substances, such as a rock containing several different minerals or a mineral that displays solid solution, this melt can be different from the bulk composition of the soli ...
of the
subducting 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 ...
plate and its sediments and of mantle
peridotite Peridotite ( ) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg2+), reflecting the high pr ...
, and fractional crystallization of ascending magma in the crust. The earliest volcanic activity on the west coast of
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...
goes back to the
Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
, when the
South Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe a ...
started to open. During the late
Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configu ...
, a volcanic chain was formed on top of
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 Cretace ...
and
Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ...
rocks and reached a width of in the area of Lastarria. This volcanism began 25million years ago, and the rocks are mostly
acidic rock Acidic rock or acid rock refers to the chemical composition of igneous rocks that has 63% wt% SiO2 content. Rocks described as acidic usually contain more than 20% of free quartz. Typical acidic rocks are granite or rhyolite. Term is used in c ...
s.


Local

Lastarria and Cordón del Azufre form a group of volcanoes on the
Altiplano The Altiplano (Spanish for "high plain"), Collao (Quechua and Aymara: Qullaw, meaning "place of the Qulla") or Andean Plateau, in west-central South America, is the most extensive high plateau on Earth outside Tibet. The plateau is located at ...
, on the border between Chile and Argentina. They were active during the
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 year ...
. The Bayo volcano is sometimes considered part of this complex as well. Lastarria and Cordón del Azufre, together with some more local volcanic centres, may be part of a larger silicic volcanic complex that has not yet formed 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 ...
. This complex is characterized by a high doming with a central depression. The large Los Colorados caldera lies south-southeast of Lastarria. Farther south lie volcanoes such as
Wheelwright Caldera Wheelwright caldera is a caldera in Chile. It is variously described as being between and wide and lies in the Central Volcanic Zone of the Andes. A lake lies within the caldera, which is among the largest of the Central Andes. The caldera lies i ...
and Cerro Blanco, the last of which shows evidence of recent unrest. Lastarria is located on a
basement A basement or cellar is one or more Storey, floors of a building that are completely or partly below the storey, ground floor. It generally is used as a utility space for a building, where such items as the Furnace (house heating), furnace, ...
formed by andesite–dacite volcanic rocks in the form of ignimbrites, lava flows, and lava domes. They 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 ...
to
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 ...
age and are in turn underlaid by
Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ...
metamorphized volcanic and sedimentary rocks. The basement underneath Lastarria appears to have a different composition to that beneath
Lascar A lascar was a sailor or militiaman from the Indian subcontinent, Southeast Asia, the Arab world, British Somaliland, or other land east of the Cape of Good Hope, who was employed on European ships from the 16th century until the middle of the ...
. A major crustal lineament known as the Archibarca lineament intersects the main volcanic arc at Lastarria. Other volcanic centres such as Galán and ore deposits are also found on this lineament. The intersection between this lineament and the arc may act as a weakness zone that focuses the ascent of
magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natura ...
. Other lineaments in the region include the Imilac-Salina del Fraile and Pedernales-Arizaro faults 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 ...
age.


Geologic record

The
Altiplano The Altiplano (Spanish for "high plain"), Collao (Quechua and Aymara: Qullaw, meaning "place of the Qulla") or Andean Plateau, in west-central South America, is the most extensive high plateau on Earth outside Tibet. The plateau is located at ...
started to form during the
Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...
, when subduction of the Nazca Plate beneath the South American Plate caused compression along the plate margin. Strong volcanism and tectonic uplift occurred between 15and 20million years ago.


Composition

Lastarria is composed of rocks ranging from
basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...
over
andesite 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 predo ...
to
dacite 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 rhyo ...
, and the rocks define a
potassium Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
-rich suite characteristic of
calc-alkaline The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic m ...
magmas of the Central Volcanic Zone. The appearance of Lastarria lavas is
porphyritic Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning a ...
.
Phenocryst 300px, feldspathic phenocrysts. This granite, from the Switzerland">Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coins, 1 euro coin (diameter ...
s include
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 p ...
in andesite with smaller amounts of
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 ...
,
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 ...
,
clinopyroxene 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 I ...
, and
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 I ...
.
Apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common ...
and
zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of t ...
form
accessory mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
s. Dacites have similar composition but also contain
hornblende Hornblende is a complex 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 in igneous and metamorphic rock ...
.
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 qui ...
is found in the andesites and
quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical f ...
in the dacites. A number of
alteration Alteration(s) may refer to: * Alteration (music), the use of a neighboring pitch in the chromatic scale in place of its diatonic neighbor. ** Alteration, in the mensural notation used by renaissance music, the lengthening of a breve, semibreve or ...
products are also present, some of which have been visualized by aerial imagery. Fumarole deposits contain encrustations and sublimates. They broadly consist of several components, mainly native
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
,
sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...
s like
anhydrite Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...
,
baryte Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate ( Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...
,
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...
and
rhomboclase Rhomboclase is an acidic iron sulfate mineral with a formula reported as H5Fe3+O2(SO4)2·2(H2O)http://www.handbookofmineralogy.org/pdfs/rhomboclase.pdf Handbook of Mineralogy or HFe(SO4)2·4(H2O).http://www.mindat.org/min-3410.html Mindat It cryst ...
,
borate A borate is any of several boron oxyanions, negative ions consisting of boron and oxygen, such as orthoborate , metaborate , or tetraborate ; or any salt with such anions, such as sodium metaborate, and disodium tetraborate . The name also re ...
s like
sassolite Sassolite is a borate mineral, specifically the mineral form of boric acid. It is usually white to gray, and colourless in transmitted light. It can also take on a yellow colour from sulfur impurities, or brown from iron oxides. History and occ ...
,
oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...
s like
quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical f ...
and less commonly
sulfide Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds la ...
s like
galena Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver. Galena is one of the most abundant and widely distributed sulfide minerals. It cr ...
,
orpiment Orpiment is a deep-colored, orange-yellow arsenic sulfide mineral with formula . It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and is formed both by sublimation and as a byproduct of the decay of anothe ...
and
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...
.
Cristobalite Cristobalite is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, SiO2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the ...
and
magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With ...
are found in high-temperature vents. These form multicoloured deposits, ranging from yellow-white over grey to yellow-orange and red. The petrogenesis of Lastarria rocks, like those of other volcanoes in the Central Volcanic Zone, involves the prolonged interaction with crustal rocks in magma chambers as well as the fractionation of certain minerals. Enriched lower crust and
upper mantle The upper mantle of Earth is a very thick layer of rock inside the planet, which begins just beneath the crust (at about under the oceans and about under the continents) and ends at the top of the lower mantle at . Temperatures range from appr ...
might also contribute. Finally, the mixing of magma chamber contents with new and more
mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks in ...
magma shortly before each eruption played an important role in rock genesis. In the case of Lastarria, this mixing occurs in a stratified magma chamber, with active
convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the c ...
occurring between lighter and colder upper contents and hotter and denser lower contents. Some rocks display "banding" features, implicating the mixing of different magmas during their formation. Some chemical differences exist among the Negriales rocks, the Lastarria lavas, and the Lastarria pyroclastics. The Negriales rocks are the richest in
silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
, and their
trace element __NOTOC__ A trace element, also called minor element, is a chemical element whose concentration (or other measure of amount) is very low (a "trace amount"). They are classified into two groups: essential and non-essential. Essential trace elements ...
composition sharply diverges as well. The Negriales rocks may originate from parental magmas that are different from the main Lastarria magmas.


Climate and vegetation

Lastarria has a montane climate characterized by extreme aridity as it is located at the intersection between the summer rain region of the Altiplano and the
Atacama Desert The Atacama Desert ( es, Desierto de Atacama) is a desert plateau in South America covering a 1,600 km (990 mi) strip of land on the Pacific coast, west of the Andes Mountains. The Atacama Desert is the driest nonpolar desert in th ...
. Temperatures of and precipitation of have been recorded on Lastarria, although the precipitation may be underestimated. Low bush vegetation exists in the area.


Eruptive history

The South Spur edifice is the oldest structure found at Lastarria. The Negriales lava field formed later. The five craters of Lastarria proper formed in five different stages. An alternative view holds that Negriales formed before the South Spur, and that the main edifice formed in ten different stages. Block-and-ash flows, hot avalanches, lava domes, lava flows, and pyroclastic flows have all been involved in the activity of Lastarria. Most deposits on the northern slopes were erupted during the last two stages, with the exception of several exposures of the older stages on the northwestern flank and the western "pink pyroclastic flow" deposit. Overall, later and
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 togeth ...
activity at Lastarria was highly
explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An expl ...
, unlike the more effusive earlier eruptions including the Negriales eruptions. Potassium–argon dating of Lastarria has yielded ages of 600,000 ± 300,000 and less than 300,000 years ago. The older date refers to the Negriales lava field, which has also been dated at 400,000116,000 ± 26,000 years ago. The South Spur is dated at 150,000 ± 50,000 years ago. The main edifice started forming 260,000 ± 20,000 years ago. One andesite lava flow was dated at 51,000 ± 13,000 years ago by
argon–argon dating Argon–argon (or 40Ar/39Ar) dating is a radiometric dating method invented to supersede potassiumargon (K/Ar) dating in accuracy. The older method required splitting samples into two for separate potassium and argon measurements, while the newer ...
. There was then a lull in volcanic activity until 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 togeth ...
. Three
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 surro ...
s were erupted during the Holocene between 4,850 ± 40 and 2,460 ± 40 years ago and were emplaced around the volcano, in particular north and west of the edifice. Most of the volcano formed post-
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 betwe ...
ly.
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 togeth ...
explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma su ...
s were separated by intervals of about 2,390 - 1,660 years. Three
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 surro ...
s were erupted during the Holocene between 4,850 ± 40 and 2,460 ± 40 years ago and were emplaced around the volcano, in particular north and west of the edifice.Three
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 surro ...
s were erupted during the Holocene between 4,850 ± 40 and 2,460 ± 40 years ago and were emplaced around the volcano, in particular north and west of the edifice. The landslide also occurred during the Holocene, 7430 (+136,−156) years before present. The lava dome on the northernmost crater rim is the youngest vent of Lastarria. The youngest dated deposit is 2,460 ± 50/60 years old, but at least one younger pyroclastic flow is present. No historical eruptions are known but
earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fr ...
s have been recorded at the volcano. Noticeable thermal hotspots are visible from ASTER imagery and are associated with the fumarolic areas. Temperatures observed at the hotspots are around . A potential of
geothermal power Geothermal power is electrical power generated from geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation is currently used in 2 ...
at Lastarria was recognized already in 1974. It is considered Argentina's 9th most dangerous volcano out of 38.


Fumarolic activity

Lastarria displays vigorous
fumarolic A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volc ...
activity on the summit and down the northwestern slopes. Such activity has been observed since the European discovery of Lastarria, in the late 19thcentury. Lastarria is the only volcano in the area with ongoing fumarolic activity. It manifests in fumaroles forming high chimneys, small cones reaching heights of , wide craters, fractures, in a diffuse fashion through pyroclastic deposits, as well as degassing through cracks and fissures on surfaces. Individual fumaroles have been found in the craters, on the crater edges, and on the slopes. A northwest–southeast striking fracture is associated with some of the fumaroles. Four different fumarole fields have been found, one along this fissure on the northwestern slope at altitudes of about , two on the rims of the fourth crater, and one in the fifth crater. The fissure field is the largest, covering a surface area of , while the other fields can be as small as . The alignment of fumarolic vents suggest that their position is controlled by the structure of the volcano. The fumaroles release gases with temperatures ranging from .
Carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
is the most important non-hydrous component of the gases; other components are
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...
in variable amounts,
hydrogen chloride The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chlorid ...
,
hydrogen fluoride Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock ...
,
hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The under ...
, and variable amounts of
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
and
sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic a ...
. Additional components are
alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in wh ...
s,
alkenes In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, a ...
,
argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice a ...
,
carbon monoxide Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simpl ...
especially in hotter fumaroles,
helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic ta ...
,
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane ...
, and
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
. The composition of the fumaroles indicates that most gases are of magmatic origin with little contribution from the atmosphere. Likewise, most water comes from the magma rather than from precipitation, as indicated by the oxygen isotope ratios. It is likely that the arid climate of the region reduces the input of meteoric water to the volcanic system. Of five volcanoes analyzed in 2012 (
Lascar A lascar was a sailor or militiaman from the Indian subcontinent, Southeast Asia, the Arab world, British Somaliland, or other land east of the Cape of Good Hope, who was employed on European ships from the 16th century until the middle of the ...
, Lastarria, Ollague,
Putana In Hinduism, Pūtanā () is a rakshasi (demoness), who was killed by the infant-god Krishna. Putana disguises as a young, beautiful woman and tries to kill the god by breast-feeding poisoned milk; however Krishna sucks her milk as well as her l ...
, and San Pedro), Lastarria had the highest flux rates. Individual gas fluxes in tons per day are registered as: The composition of Lastarria's gases has changed over time, with an increase in the magmatic component between 2009 and 2012, which may be due either to different measurement methods or to changes in the volcanic activity at Lastarria. Decreased temperatures have been observed after rainfall. The gases of Lastarria come from a geothermal system and, with temperatures ranging from and , supply the colder and hotter fumaroles, respectively. In turn, a magma system at depths of underpins and feeds this geothermal system. During their rise, the gases interact with the rocks of the surrounding country and with
aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials ( gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characte ...
s.
Arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, b ...
is a harmful pollutant that occurs in above average concentrations in waters of northern Chile. Fumarolic exhalations at Lastarria can reach over of the fumarole sediments and the volcano is considered to be an important source of arsenic of the southern Central Volcanic Zone.


Sulfur

The
fumarole A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...
s on Lastarria have created widespread deposits of
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
. The sulfur has also formed flows, of which the two largest are and long. The longer flow is partly buried by the shorter one and has already lost part of its surface structure. No vents have been found; sulfur flows appear to emerge from the fumarolic terrain. One
andesite 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 predo ...
lava flow has generated several subsidiary sulfur flows that resemble
pahoehoe 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 ...
flows and have widths of . It is likely that sulfur deposited by fumaroles formed such flows. Some fumaroles currently release centimetre-long sulfur flows. Flows of sulfur are highly fragile constructs that can easily be destroyed. The conditions surrounding the emplacement of the sulfur have caused the sulfur to assume various colours, including black, brown-orange, orange, red, yellow, and yellow-orange. These colours vary along the length of the flows and between various flows, indicating that temperatures varied between one flow and another. Liquid sulfur has different
viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the int ...
and rheomorphic properties at different temperatures, and some variation occurred at Lastarria's flows as well. Such sulfur flows are rare on
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
; they may be more common on the
Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...
moon Io. On Earth, they have been found at
Kawah Ijen Map of Ijen Crater, where sulfur is mined The Ijen volcano complex is a group of composite volcanoes located on the border between Banyuwangi Regency and Bondowoso Regency of East Java, Indonesia. It is known for its blue fire, acidic crate ...
in
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Gui ...
, Mount Iō (Shiretoko) in
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
,
Mauna Loa Mauna Loa ( or ; Hawaiian: ; en, Long Mountain) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaii in the Pacific Ocean. The largest subaerial volcano (as opposed to subaqueous volcanoes) in both mass and ...
on
Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...
,
Momotombo Momotombo is a stratovolcano in Nicaragua, not far from the city of León. It stands on the shores of Lago de Managua. An eruption of the volcano in 1610 forced inhabitants of the Spanish city of León to relocate about west. The ruins of th ...
in
Nicaragua Nicaragua (; ), officially the Republic of Nicaragua (), is the largest country in Central America, bordered by Honduras to the north, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the west. Managua is the coun ...
, and
Sierra Negra Sierra Negra (also, and perhaps more properly, Cerro La Negra) is an extinct volcano located in the Mexican state of Puebla, close to the border with Veracruz. At officially above sea level, it is the fifth-highest peak in Mexico. Sierra Neg ...
on the Galapagos Islands. The sulfur flows on Lastarria may be threatened by future
mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the econom ...
efforts in the region.


Ground uplift

InSAR Interferometric synthetic aperture radar, abbreviated InSAR (or deprecated IfSAR), is a radar technique used in geodesy and remote sensing. This geodetic method uses two or more synthetic aperture radar (SAR) images to generate maps of surface defo ...
observations performed in the years 1998 to 2000 have yielded evidence of a pattern of ground uplift centered between Lastarria and Cordón del Azufre. This pattern, also known as "Lazufre", covers a surface area of . This uplift appears to be caused by the injection of magma at depth, with a pattern of progressively increasing flux between 2003 and 2006. The source of this uplift appears to lie at depths of , later recalculated at . This uplift may have been ongoing for about 400,000 years and has influenced the final position of lava flows of Lastarria and other volcanoes in the area. Ground uplift has been detected at Lastarria itself, amounting to . The uplifting region has either a surface area of or is wide, smaller than Lazufre. The Lastarria uplift started later than the Lazufre uplift and may be influenced by the latter. Possibly, magma injected into a Lazufre magma chamber is influencing the Lastarria hydrothermal system, with changes in fumarole output observed in 2006–2012. Modelling indicates that the source of this uplift lies at a depth of about and has the shape of a sphere. Another estimate places the source inside the volcanic edifice and assumes a size of , with the volume increasing by about . Ground uplift is still underway but with a slowdown between 2006 and 2016. At other volcanoes, such uplift has been associated with changes in fumarolic activity or even the start of an eruption.


Threats

The volcano is in a remote area and thus constitutes little risk to human settlements. The closest populations are at , , and . The Chilean
SERNAGEOMIN 250px, Sernageomin building in Providencia, Santiago. The National Geology and Mining Service ( es, Servicio Nacional de Geología y Minería; SERNAGEOMIN) is a Chilean government agency. Its function is to provide geological information and adv ...
published a volcano alert rating for Lastarria. A permanent
seismometer A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The outpu ...
was installed on the volcano in late 2013. It is considered the 45th most dangerous volcano in Chile.


See also

*
Cerro Escorial Cerro Escorial is a stratovolcano at the border of Argentina and Chile. It is part of the Corrida de Cori volcanic group and its youngest member. A well-preserved crater forms its summit area. Lava flows are found on the Chilean and smaller one ...
*
Corrida de Cori Corrida de Cori is a mountain range in Argentina and Chile. It consists of several aligned volcanoes, including Cerro Escorial, which exceed in elevation. The range, together with several local volcanoes, forms an alignment that may be control ...
*
List of volcanoes in Chile The Smithsonian Institution's Global Volcanism Program lists 105 volcanoes in Chile that have been active during the Holocene.List of volcanoes in Argentina This is a list of active and extinct volcanoes in Argentina. Volcanoes {, class="wikitable sortable" style="text-align:right;" , - style="text-align:center;" ! rowspan="2" , Name ! rowspan="2" , Type ! colspan="2" , Elevation ! Location ...


References


Bibliography

* * * * * * * * * * * * * * * * * * * * * * *


External links


AVA Images
*
SERNAGEOMIN

Photo of Lastarria volcano

View of the fumaroles near the top of Lastarria, Llullaillaco volcano in the distant background
{{Andean volcanoes Volcanoes of Antofagasta Region Volcanoes of Catamarca Province Volcanoes of Salta Province Stratovolcanoes of Chile Subduction volcanoes Polygenetic volcanoes Pleistocene stratovolcanoes Holocene stratovolcanoes Mountains of Argentina Mountains of Chile Argentina–Chile border International mountains of South America Puna de Atacama Mountains of Antofagasta Region Mountains of Salta Province