Tilocálar is a group of
volcanoes south of the
Salar de Atacama, in Chile. It developed during the
Pleistocene and consists of a small
lava dome, two vents with numerous thick
lava flows that reach lengths of several kilometres, and an
explosion crater that was mistaken for an
impact crater in the past. There are similar volcanoes nearby.
The southern vent (Tilocálar Sur) is the larger.[1] It produced six[4] or four
lava flows with a total volume of about 0.24 cubic kilometres (0.058 cu mi).
Pyroclastic deposits cover an area of 3.3 square kilometres (1.3 sq mi),[5] forming a roughly circular area where the lava flows were emplaced.[6] It has three
volcanic craters aligned on a
graben[7] and the lava flows probably emanated from a
lava lake.[8]
The northern vent of Tilocálar produced only one 4.3-kilometre (2.7 mi) long flow,[9] which covers an area of about 3.5 square kilometres (1.4 sq mi) and consists of three separate
geologic units.[10]
A small
lava dome is situated southwest of Tilocálar north[11] and is called El Maní;[6] it resembles a pile of rocks.[12]
An
explosion crater lies 1 kilometre (0.62 mi) south of Tilocálar Sur[1] and has also been described as a
maar.[13] This crater has a diameter of 400–300 metres (1,310–980 ft) and a depth of 50 metres (160 ft), and bears traces of having been filled with water in the past. It was discovered in 1976 during field work and originally was interpreted to be an
impact crater,[14] but does not have the properties of one.[4]
The lava flows emanating from Tilocálar are 50–80 metres (160–260 ft) thick and blocky.[10] A
dyke swarm is associated with the vents.[15] The Tilocálar volcanoes are situated within a geographical depression[10] associated with numerous north-south trending ridges; the volcanism at Tilocálar is geographically linked to these ridges.[16] Other volcanoes such as
Cerro Tujle[17] and Negro de Aras are in the vicinity.[18]
Geology
The volcanoes developed on
ignimbrites of
Pliocene age,[1] which are alternatively identified as the Talabre[9] or the Tucucaro ignimbrite;[15] the latter is 3.2±0.3 million years old.[19] The region is subject to
compressional tectonic forces,[20] and a
Plio-Pleistocene north-south trending
fault system played a role in the development of the volcano.[21]Magnetotelluric analysis has identified electrically conductive structures underneath Tujle and Tilocálar, which may either by
hydrothermally altered rocks or partial melt left over from past
magmatic processes.[22]
Between Bolivia, Chile and Argentina, an area of volcanoes exceeding 50,000 square kilometres (19,000 sq mi) constitutes the
Altiplano-Puna volcanic complex.[23] These volcanoes were active during the last 26 million years in distinct pulses, most recently one million years ago at
Apacheta-Aguilucho volcanic complex,
El Tatio and
Purico. The pulses are characterized by the emission of ignimbrites and the formation of
calderas. These volcanic units are
silicic, but more
mafic volcanic units were also emplaced in the region in the form of
monogenetic volcanoes such as Tilocálar.[13]
The volcanoes were active during the
Quaternary,[15]Pleistocene-
Holocene[1] or in the last 900,000 years.[30] Dating has yielded ages of less than one million years,[31] and
argon–argon dating on Tilocálar Sur has produced ages of 730,000±500,000 and 460,000±50,000 years.[7] There are no known historical eruptions and has not been assigned a hazard score; potential impacts of renewed activity on populations are considered to be minimal.[32]
North Tilocálar formed during a single eruption, while Tilocálar Sur was constructed during multiple eruptions.[15] Presumably an initial
explosive eruption emplaced the pyroclastics, which were then in part overrun by the lava flows.[33] The event had a
volcanic explosivity index of 3–4.[34] The explosion crater was probably formed through a steam or gas explosion when the conduit of Tilocálar Sur was breached[4] and interacted with a regional confined
groundwater body.[35]
^Cembrano, J. (2008). The interplay between crustal tectonics and volcanism in the Central and Southern Volcanic zones of the Chilean Andes. International Symposium on Andean Geodynamics. No. 7 – via
ResearchGate.
^Loughlin, Susan C.; Sparks, Robert Stephen John; Sparks, Steve; Brown, Sarah K.; Jenkins, Susanna F.; Vye-Brown, Charlotte (24 July 2015).
Global Volcanic Hazards and Risk(PDF). Cambridge University Press. p. 604.
ISBN978-1-107-11175-2. Archived from the original on August 19, 2016. Retrieved 30 August 2021.{{
cite book}}: CS1 maint: unfit URL (
link)