| Tata Sabaya | |
|---|---|
 | |
| Highest point | |
| Elevation | 5,430 m (17,810 ft)[1] |
| Coordinates | 19°08′S68°32′W / 19.133°S 68.533°W /-19.133; -68.533[2] |
| Geography | |
  Tata Sabaya | |
Tata Sabaya is a 5,430-metre (17,810 ft) highvolcano inBolivia. It is part of theCentral Volcanic Zone, one of severalvolcanic belts in the Andes which are separated by gaps without volcanic activity. This section of the Andes was volcanically active since theJurassic, with an episode of strongignimbritic volcanism occurring during theMiocene. Tata Sabaya lies in a thinly populated region north of theSalar de Coipasasalt pan.
Volcanic activity at Tata Sabaya and elsewhere in the Central Volcanic Zone is the consequence of thesubduction of theNazca Plate beneath theSouth America Plate. The volcano has developed along alineament that separates oldercrust north of the lineament from younger crust in the south, and the edifice has been formed byandesitic rocks.
The southern flank of Tata Sabayafailed during the latestPleistocene about 12,000–12,360 years before present. Debris from the collapse entered a lake that covered the Salar de Coipasa at that time and formed a deposit with a volume of 6 ± 1 cubic kilometre (1.44 ± 0.24 cu mi). Subsequently, the collapse scar was partly filled in with more recentlava flows andlava domes; one eruption occurred about 6,000 yearsbefore present.
Tata Sabaya lies just north of theSalar de Coipasa inBolivia. The small village ofPagador lies west-southwest of the volcano,[3] but the whole region is overall thinly inhabited.[4] The name means "Father Sabaya"; the term "Sabaya" may be theAymara corruption of theQuechua term for "devil", "demon".[5] The volcano, which features a summit sanctuary,[6] is a topic in local myths, where it is sometimes personified,[7] and subject of a ritual involving it and neighbouring volcanoes.[8]
Tata Sabaya is part of theCentral Volcanic Zone of the Andes,[9] which consists of avolcanic arc that mainly follows theWestern Cordillera. There are about 44Holocene volcanoes, however the remoteness of the region and dry climate has restricted scientific research of these volcanoes; among the better known areLastarria, theNevados de Payachata,Ollagüe,San Pablo,San Pedro andSocompa.[2]
Tata Sabaya is a volcano which reaches a height of 5,430 metres (17,810 ft).[1][10] Fivelava flows extend north from the summit and display levees and flow fronts, the flows reaching a maximum length of 2 kilometres (1.2 mi). The top of these flows is cut by a collapse scar that extends east and west of the edifice in the form ofscarps up to 50 metres (160 ft) high.[11] The space between the scarps is in turn filled by more recent lava flows with a blocky appearance.[12] Farther away of the edifice, the scarp is more noticeable and reaches a height of about 200 metres (660 ft) on the southeastern side of the volcano.[10]
A 300-square-kilometre (120 sq mi) large deposit south of the volcano, originally interpreted as anuee ardente deposit, is actually alandslide deposit[2] which extends over a length of 20 kilometres (12 mi) and a width of 7 kilometres (4.3 mi);[13] its volume is about 6 ± 1 cubic kilometre (1.44 ± 0.24 cu mi).[14] The landslide incorporated material from the salar,[15] and its rocks reflect in part the layering and structure of the pre-collapse volcano.[14] The deposit is one of the more conspicuous of its type, to the point that it was observed and identified on low-resolutionLandsat images.[10] It consists of material that formshummock-like deposits, with individual hummocks becoming smaller the farther away from the edifice they are.[11] The deposit extends into the Salar de Coipasa where it is confined byfaults[13] and is in part covered by lacustrine sediments such astufa.[11]
Off the western coast of South America, theNazca Platesubducts beneath theSouth America Plate[16] at a rate of about 10 centimetres per year (3.9 in/year).[17] This subduction process is responsible for the volcanism in theAndean Volcanic Belt, which occurs in aNorthern Volcanic Zone in Ecuador and Colombia, aCentral Volcanic Zone in Peru, Bolivia, Chile and Argentina and aSouthern Volcanic Zone in Chile and Argentina. These volcanic zones are separated by gaps without volcanism, where the subduction process is shallower.[18]
Several phases of tectonic and volcanic activity have been identified in the Central Volcanic Zone. An earlier phase of volcanism in theCordillera de la Costa commenced in theJurassic but is considered separate from the Central Volcanic Zone magmatism proper. After an erosional hiatus during theOligocene,volcanic arc activity increased during theMiocene and culminated in a phase of strongignimbrite eruptions,[9] which originated incalderas. This phase was associated with a substantial thickening of thecrust in the Central Andes. During thePleistocene ignimbrite volcanism waned again andstratovolcanoes began to develop.[2]
Tata Sabaya lies along a crustal transition area which separates a youngercrust farther south from an older (Proterozoic) crust in the north,[2] which is made up by theChileniaterrane and theArequipa-Antofallacraton, respectively. This transition area appears to coincide with a chain of volcanoes that Tata Sabaya is part of and which extends fromCerro Saxani in the east toIsluga in Chile, as well as with the northern end of thePica gap where no recent volcanism occurs in the volcanic arc.[17]
The basement of the volcano is formed by the ignimbritic Altos de Picaformation, although outcrops ofgranite have been observed in the region;[17] one of these outcrops may be aPrecambrian granite subsequently thermally modified in theToarcian.[19] This basement is covered by younger volcanic rocks,alluvium and sediments of the Salar de Coipasa.Seismic tomography suggests that moltenmagma exists in the regional crust.[17]
Tata Sabaya has produced "two-pyroxene"andesite andporphyritic andesite.[20] Minerals contained within the rock areaugite,biotite,hornblende,hypersthene,plagioclase andtitanomagnetite with only little variation between rocks erupted during separate stages of volcanic activity.[21] The erupted volcanites define apotassium-richcalc-alkaline suite. Inclusions of moremafic[a] rocks in the erupted material may indicate that mafic magma was injected into themagma chamber of Tata Sabaya.[12] The magma genesis at Tata Sabaya has been explained with magma mixing processes, which gave rise to a fairly uniform composition of the eruption products.[23]
The region is dry with precipitation mainly falling during southern hemisphere summer, and has little vegetation cover.[4]Polylepis tarapacana trees grow on the slopes of Tata Sabaya; these trees form the highest woodlands in the world.[24] Other aspects of regional vegetation are the so-calledpunasteppe, which is characterized by grass andshrub vegetation.[25]
Of all volcanoes in Bolivia, Tata Sabaya is the only one with Holocene activity which is not on the border with another country.[2] The young age of the mountain has been inferred from the lack ofglaciation[1] andmoraines on the mountain,[10] unlike neighbouring summits.[1]
The earliest activity at Tata Sabaya constructed apyroclastic shield, which crops out as a 20-metre (66 ft) thick sequence of block-and-ash flowsfallout deposits andpumice deposits in the northern sector of the volcano.[17]Effusive eruptions then built up a volcanic cone on top of this shield; the five northerly lava flows were emplaced during this phase of activity. Some lava flows from this stage were unstable and collapsed, covering the northern parts of the volcano with debris.[26]
This effusive activity eventually oversteepened the cone, causing its southern sector to collapse. During this collapse andlandsliding, largetoreva blocks developed from sectors of the cone which slid down undeformed, while other material from the cone formed the hummocks in the sector collapse deposit;[11] there was no explosive eruption at the time of the collapse. The configuration of the deposit indicates that the debris entered the Salar when it was filled with water; the height of the tufa deposits imply that water levels were about 3,700 metres (12,100 ft) above sea level. This[12] and the lake terraces that the landslide overran marks the collapse as synchronous with theLake Tauca episode 12,000-12,360 years ago[12][10] when water levels in the Salar de Coipasa reached their maximum.[27] The onset of such collapses on volcanoes is often determined by faulting, climate change or eruption of the volcano; at Tata Sabaya earthquakes and the injection of new magma has been invoked to explain the destabilization of the edifice.[14]
After the collapse, Holocene activity filled the scar withlava domes and lava flows, cancelling the traces of the collapse;[27] some of these in turn collapsed as well and gave rise to hot avalanche deposits.[12]Radiocarbon dating for apyroclastic flow has yielded an age of 6,000 yearsbefore present, implying that the volcano may be still active.[28] Reportedly, when in 1600Huaynaputina erupted in Peru a volcano named Sabaya erupted inOruro and destroyed a village.[29]
