Tumisa

Tumisa
Cerro Tumisa
Tumisa
Highest point
Elevation 5,658 m (18,563 ft) [1]
Coordinates 23°28′S 67°49′W / 23.467°S 67.817°W / -23.467; -67.817Coordinates: 23°28′S 67°49′W / 23.467°S 67.817°W / -23.467; -67.817 [1]
Geography
Parent range Andes
Geology
Age of rock Pleistocene
Mountain type Stratovolcano
Volcanic belt Central Volcanic Zone
Last eruption 500,000 years ago

Tumisa (also known as Cerro Tumisa) is a Pleistocene stratovolcano in the Andes. Located east of the Salar de Atacama, it is part of the Central Volcanic Zone, which since the Miocene has been subject to extensive andesitic/dacitic effusive activity and ignimbrite eruptions. The basement on which Tumisa is built includes Paleozoic rocks and more recent volcanic products of the Lejia volcano and the Atana and Patao ignimbrites.[2]

Block flows, lava flows, lava domes and some ignimbrites of pumiceous composition form this composite volcano.[3] More than six lava domes and two major cones are part of this system and surrounded by a pyroclastic apron,[4] which covers a surface area of 300 square kilometres (120 sq mi) and is formed from many pyroclastic flows with a total volume of 21 cubic kilometres (5.0 cu mi). The pyroclastic flows contain pumice and large blocks, some of which show signs of deformation when they were still hot. The lava domes and lavas are grouped in three units. Presumably, the activity of Tumisa started with explosive eruptions that generated the ignimbrite apron, later degassed magma formed the lava domes and lava flows.[2]

Dating of the volcano indicates that it becomes younger with higher altitude, a pattern that may be explained either by a shift in the magmatic system or a progressive downslope sliding of the volcano during its history at a speed of 0.5–2 centimetres per year (0.20–0.79 in/year). This interpretation is supported by the drainage patterns of the volcano, with channels bending outwards and curving towards the west. These channels possibly formed over faults of the slipping volcano.[4] Valleys (quebradas) were excavated less than one million years ago during the glacial stages in Tumisa's northern flank. Moraines are also found.[5]

The volcano has erupted dacitic lavas containing andesitic mafic inclusions. These inclusions resemble those from the Soncor flow of neighbouring Lascar to the northeast. Some rocks may have been influenced by the interaction with calcium carbonate in the magma chambers.[6] Hornblende crystals with dimensions of 5–10 millimetres (0.20–0.39 in) and megacrysts of feldspar with dimensions of up to 1.5 centimetres (0.59 in) are also present.[5] The textures of the products suggest that magma mixing occurred during activity.[7] The dacites have a white porphyritic appearance. The dome complex is dated 2.5-0.5 mya and the associated pyroclastics 1.5-0.5 mya and constructed on Tertiary ignimbrites.[8] One date of 1.2±0.6 million years was obtained from the Las Mulas dome.[2] The complex is of Pleistocene age.[3] Later, hydrothermal alteration occurred.[2]

A fault with probably postglacial activity crosses the Laguna Lejia and is associated with Tumisa, connecting Tumisa with a basaltic maar and an isolated lava dome. It runs in northwest-southeast direction and crosses Lejia on its southern margin.[9]

Tumisa and its neighbouring mountains Lausa, Chiliques, Ipira and Miniques are identified by the inhabitants of Socaire to be part of a giant human left hand with dimensions of 40 by 30 kilometres (25 mi × 19 mi) on the eastern horizon.[10]

References

  1. 1 2 Gonzalez-Ferran, Oscar (1994). Volcanes de Chile (1. ed.). Santiago, Chile: Instituto geografico militar. p. 183. ISBN 9562020541. Retrieved 11 October 2015.
  2. 1 2 3 4 Gardeweg, Moyra P (1988). "Petrografia y geoquimica del complejo volcánico Tumisa, Altiplano de Antofagasta, Andes del Norte de Chile" (PDF). biblioserver.sernageomin.cl (in Spanish). Santiago: SERNAGEOMIN. Archived from the original (PDF) on 11 October 2015. Retrieved 11 October 2015.
  3. 1 2 Matthews, S. J. (1999). "Empirical Calibration of the Sulphur Valence Oxygen Barometer from Natural and Experimental Glasses: Method and Applications". Mineralogical Magazine. 63 (3): 421–431. doi:10.1180/002646199548510. Retrieved 11 October 2015.
  4. 1 2 Wooller, Luke; van Wyk de Vries, Benjamin; Murray, John B.; Rymer, Hazel; Meyer, Stephanie (2004). "Volcano spreading controlled by dipping substrata". Geology. 32 (7): 573. doi:10.1130/G20472.1. Retrieved 11 October 2015.
  5. 1 2 GARDEWEG, M. C.; SPARKS, R. S. J.; MATTHEWS, S. J. (1 February 1998). "Evolution of Lascar Volcano, Northern Chile". Journal of the Geological Society. 155 (1): 89–104. doi:10.1144/gsjgs.155.1.0089. Retrieved 11 October 2015.
  6. ↑ MATTHEWS, S. J.; JONES, A. P.; GARDEWEG, M. C. (1 April 1994). "Lascar Volcano, Northern Chile; Evidence for Steady-State Disequilibrium". Journal of Petrology. 35 (2): 401–432. doi:10.1093/petrology/35.2.401. Retrieved 11 October 2015.
  7. ↑ MATTHEWS, S. J.; JONES, A. P.; BRISTOW, C. S. (1 December 1992). "A simple magma-mixing model for sulphur behaviour in calc-alkaline volcanic rocks: mineralogical evidence from Mount Pinatubo 1991 eruption". Journal of the Geological Society. 149 (6): 863–866. doi:10.1144/gsjgs.149.6.0863. Retrieved 11 October 2015.
  8. ↑ Calder, E.S.; Sparks, R.S.J.; Gardeweg, M.C. (December 2000). "Erosion, transport and segregation of pumice and lithic clasts in pyroclastic flows inferred from ignimbrite at Lascar Volcano, Chile". Journal of Volcanology and Geothermal Research. 104 (1-4): 201–235. doi:10.1016/S0377-0273(00)00207-9. Retrieved 11 October 2015.
  9. ↑ Matthews, Steve; Vita-Finzi, Claudio (23 September 1993). "Neotectonics at Laguna Lejia, Atacama Desert, Northern Chile" (PDF). Horizon pleins textes. Institut de recherche pour le développement (IRD). Archived from the original (PDF) on 26 November 2006. Retrieved 11 October 2015.
  10. ↑ Moyano, Ricardo; Uribe, Carlos (2012). "EL VOLCÁN CHILIQUES Y EL "MORAR-EN-EL-MUNDO" DE UNA COMUNIDAD ATACAMEÑA DEL NORTE DE CHILE". Estudios atacameños (in Spanish). San Pedro de Atacama (43): 187–208. doi:10.4067/S0718-10432012000100010. ISSN 0718-1043. Retrieved 11 October 2015.
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