Viedma (volcano): Difference between revisions
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== Geology == |
== Geology == |
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Off the southernmost west coast of [[South America]], the [[Antarctic Plate]] [[subduct]]s beneath the [[South America Plate]] at a rate of {{convert|3|cm/year|in/year}}.{{sfn|Kilian|1990|p=301,302}} |
Off the southernmost west coast of [[South America]], the [[Antarctic Plate]] [[subduct]]s beneath the [[South America Plate]] at a rate of {{convert|3|cm/year|in/year}}.{{sfn|Kilian|1990|p=301,302}} This subduction process is responsible for volcanism in the [[Austral Volcanic Zone]].<ref name="Stern2008" /> |
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The [[basement]] consists of [[metamorphic]] rocks of [[Paleozoic]] age. Outcrops of the basement are found around the volcano and could even occur on the edifice that crops out from the glaciers.{{sfn|Kobayashi|Orihashi|Hiarata|Naranjo|2010|p=438}} |
The [[basement]] consists of [[metamorphic]] rocks of [[Paleozoic]] age. Outcrops of the basement are found around the volcano and could even occur on the edifice that crops out from the glaciers.{{sfn|Kobayashi|Orihashi|Hiarata|Naranjo|2010|p=438}} |
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==References== |
==References== |
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{{reflist|refs= |
{{reflist|refs= |
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<ref name="Stern2008">{{cite journal|last1=Stern|first1=Charles R.|title=Holocene tephrochronology record of large explosive eruptions in the southernmost Patagonian Andes|journal=Bulletin of Volcanology|date=1 February 2008|volume=70|issue=4|page=435|doi=10.1007/s00445-007-0148-z|url=https://link.springer.com/article/10.1007/s00445-007-0148-z|language=en|issn=0258-8900}}</ref> |
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<ref name="Lliboutry1956">{{cite book|authorlink=Louis Lliboutry|last1=Lliboutry|first1=Luis|title=Nieves y glaciares de Chile: fundamentos de glaciologia|date=1956|publisher=Ediciones de la Universidad de Chile|page=413|url=https://books.google.ch/books?redir_esc=y&hl=de&id=Bo5XAAAAMAAJ&focus=searchwithinvolume&q=viedma|language=es}}</ref> |
<ref name="Lliboutry1956">{{cite book|authorlink=Louis Lliboutry|last1=Lliboutry|first1=Luis|title=Nieves y glaciares de Chile: fundamentos de glaciologia|date=1956|publisher=Ediciones de la Universidad de Chile|page=413|url=https://books.google.ch/books?redir_esc=y&hl=de&id=Bo5XAAAAMAAJ&focus=searchwithinvolume&q=viedma|language=es}}</ref> |
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<ref name="Wastegård2012">{{cite journal|last1=Wastegård|first1=Stefan|title=Tephrostratigraphy of the Potrok Aike Maar Lake Sediment Sequence|journal=Quaternary International|date=November 2012|volume=279-280|pages=528–529|doi=10.1016/j.quaint.2012.08.1843|url=http://www.sciencedirect.com/science/article/pii/S1040618212028832|issn=1040-6182}}</ref> |
<ref name="Wastegård2012">{{cite journal|last1=Wastegård|first1=Stefan|title=Tephrostratigraphy of the Potrok Aike Maar Lake Sediment Sequence|journal=Quaternary International|date=November 2012|volume=279-280|pages=528–529|doi=10.1016/j.quaint.2012.08.1843|url=http://www.sciencedirect.com/science/article/pii/S1040618212028832|issn=1040-6182}}</ref> |
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| Viedma | |
|---|---|
| Highest point | |
| Elevation | 1,500 m (4,900 ft)[1] |
| Coordinates | 49°22′S 73°19′W / 49.367°S 73.317°W[2] |
| Geography | |
| Location | Argentina/Chile |
| Parent range | Andes |
| Geology | |
| Mountain type | Subglacial volcano |
| Last eruption | November 1988[1] |
Viedma (Spanish pronunciation: [ˈbjeðma]) is a subglacial volcano located below the ice of the Southern Patagonian Ice Field, an area disputed between Argentina and Chile. The 1988 eruption deposited ash and pumice on the ice field and produced a mudflow that reached Viedma Lake.[1] The edifice of the volcano is mainly composed out of basalt or older silica-poor basement rocks, while ejecta have SiO2 contents between 62 and 66%.[3] Numerous ash layers in the Viedma lake indicate numerous past eruptions.[4]
Geography and geomorphology
Viedma is located in the southern Patagonian Andes,[5] southwest of Mount FitzRoy.[6] The lake of the same name lies southwest of the volcano. The area is poorly accessible[2] and the volcanic history poorly known.[5]
Viedma is part of the Austral Volcanic Zone.[2] This volcanic zone consists of six volcanoes, from north to south Lautaro, Aguilera, Viedma, Reclus, Monte Burney and Fueguino.[5] These volcanoes form a 700 kilometres (430 mi) long chain of volcanoes, the last of which is a volcanic complex constructed by lava domes and lava flows on Cook Island.[7]
Few things are known with certainty about the volcanic edifice of Viedma as it is mostly buried beneath glacial ice.[8] Louis Lliboutry in 1956 proposed that volcanic activity may occur in fissure vents buried beneath glaciers; between eruptions they would be concealed below the ice;[9] Lliboutry considered dark bands on the ice to be tephra deposits, a view supported by a 1958-1959 expedition that found pumice on the Viedma Glacier.[10]
Viedma Nunatak
The Viedma Nunatak is commonly interpreted to be the site of the volcano,[11] after observations made in 1944-1945 and 1950 by survey flights including controversial sightings of fumaroles which also led to the nunatak becoming known as the "Volcan Viedma";[12][9] but the difficulty of field sampling has rendered its identification with the Viedma vent contentious.[11]
The nunatak is about 1,500 metres (4,900 ft) high above sea level. Most of the mountain is buried beneath the Viedma Glacier of the Southern Patagonian Ice Field and only parts of it crop out.[2] The outcropping nunatak is elongated in north-south direction.[13] A number of structures interpreted as craters and concave depressions are found especially on the southern part of the volcano, some of which are lined up in north-south direction. The northern sector of the volcano was apparently more heavily affected by glacial erosion; conversely, several craters in the southern sector appear to be young.[14] The nunatak shows clear evidence of glacial action, including glacial striations and coverage by glacial drifts; the Viedma glacier may once have crossed the nunatak in its central part.[15] Rock samples taken from the nunatak are Jurassic metamorphic rocks, including gneiss and schists,[11] and no evidence of magmatic rocks was found in a 1958-1959 expedition.[10]
Different observations have yielded different sizes and numbers of supposed craters; González-Ferrán et al. 1995 reported several craters and calderas with sizes ranging 1.5–4 kilometres (0.93–2.49 mi), while Kobayashi et al. 2010 observed fewer craters and none of them larger than 1.5 kilometres (0.93 mi).[14] These craters were later interpreted as being actually glacial cirques containing tarn lakes.[15]
Geology
Off the southernmost west coast of South America, the Antarctic Plate subducts beneath the South America Plate at a rate of 3 centimetres per year (1.2 in/year).[16] This subduction process is responsible for volcanism in the Austral Volcanic Zone.[17]
The basement consists of metamorphic rocks of Paleozoic age. Outcrops of the basement are found around the volcano and could even occur on the edifice that crops out from the glaciers.[18]
Composition
Viedma like other volcanoes of the Austral Volcanic Zone has erupted andesite and dacite. Phenocrysts include amphibole, biotite, hypersthene and plagioclase; orthoxene, plagioclase and pyroxene also occur as xenoliths. The rocks form a calcalkaline suite,[19] but there is also an adakitic signature.[2]
The xenoliths may reflect a crustal contamination of the magma erupted at Viedma.[19]
Eruption history
Viedma has erupted during the Holocene.[8] Tephra attributed to Viedma has been found in the Laguna Potrok Aike.[20]
Historical
Many observations referring to volcanic activity on the Southern Patagonian Ice Field exist, including reports of ashfalls, layers of tephra on glaciers and columns of smoke rising from the ice.[9]
A subglacial eruption occurred in 1988, depositing ash and pumice on the Viedma Glacier. These materials later gave rise to a lahar.[2] The eruption had melted part of the ice and formed a network of valleys; it was assumed that it had taken place at some point between September and November of that year.[21]
Hazards
There are no major population centres close to any volcano in the Austral Volcanic Zone, and the volcanoes are largely unmonitored. Among the know eruptions are large Holocene explosive eruptions, while historical eruptions took place in 1908 at Reclus and 1910 at Monte Burney.[7] Future eruptions of volcanoes in the Austral Volcanic Zone may lead to ash fall at large distances from the volcano, including interruptions in air traffic and direct ash damage.[22]
See also
References
- ^ a b c "Viedma". Global Volcanism Program. Smithsonian Institution. Retrieved 2005-02-15.
- ^ a b c d e f Kobayashi et al. 2010, p. 434.
- ^ Issues in Earth Sciences, Geology, and Geophysics: 2011 Edition. ScholarlyEditions. 9 January 2012. pp. 1240–. ISBN 978-1-4649-6338-4.
- ^ Zentralblatt für Geologie und Paläontologie: Allgemeine und angewandte Geologie einschl. Lagerstättengeologie, regionale Geologie. E. Schweizerbart'sche Verlagsbuchhandlung (Erwin Nägele). 1991. p. 1713.
- ^ a b c Kilian 1990, p. 301.
- ^ Shipton 1960, p. 393.
- ^ a b Perucca, Alvarado & Saez 2016, p. 552.
- ^ a b Perucca, Alvarado & Saez 2016, p. 553.
- ^ a b c Shipton 1960, p. 389.
- ^ a b Shipton 1960, p. 391.
- ^ a b c Blampied et al. 2012, p. 380.
- ^ Lliboutry, Luis (1956). Nieves y glaciares de Chile: fundamentos de glaciologia (in Spanish). Ediciones de la Universidad de Chile. p. 413.
- ^ Kobayashi et al. 2010, p. 436.
- ^ a b Kobayashi et al. 2010, p. 435.
- ^ a b Blampied et al. 2012, p. 381.
- ^ Kilian 1990, p. 301,302.
- ^ Stern, Charles R. (1 February 2008). "Holocene tephrochronology record of large explosive eruptions in the southernmost Patagonian Andes". Bulletin of Volcanology. 70 (4): 435. doi:10.1007/s00445-007-0148-z. ISSN 0258-8900.
- ^ Kobayashi et al. 2010, p. 438.
- ^ a b Kilian 1990, p. 303.
- ^ Wastegård, Stefan (November 2012). "Tephrostratigraphy of the Potrok Aike Maar Lake Sediment Sequence". Quaternary International. 279–280: 528–529. doi:10.1016/j.quaint.2012.08.1843. ISSN 1040-6182.
- ^ Kilian 1990, p. 302.
- ^ Perucca, Alvarado & Saez 2016, p. 557.
Sources
- Blampied, Jorge; Barberon, Vanesa; Ghiglione, Matías; Leal, Pablo; Ramos, Víctor (August 2012). "Disambiguation of the Nunatak Viedma: a basement bl ock previously confused as a volcanic center" (PDF). SERNAGEOMIN. Antofagasta: 13th Chilean Geological Congress. pp. 380–382. Retrieved 19 December 2017.
{{cite web}}: Invalid|ref=harv(help) - Kilian, R. (1990). The australandean volcanic zone (south Patagonia) (PDF). Paris: ORSTOM. ISBN 2-7099-0993-6.
{{cite book}}: Invalid|ref=harv(help) - Kobayashi, Chiaki; Orihashi, Yuji; Hiarata, Daiji; Naranjo, Jose; Kobayashi, Makoto; Anma, Ryo (17 August 2010). "Compositional variations revealed by ASTER image analysis of the Viedma Volcano, southern Andes Volcanic Zone". Andean Geology. 37 (2): 433–441. doi:10.5027/andgeoV37n2-a09. ISSN 0718-7106.
{{cite journal}}: Invalid|ref=harv(help) - Perucca, Laura; Alvarado, Patricia; Saez, Mauro (1 July 2016). "Neotectonics and seismicity in southern Patagonia". Geological Journal. 51 (4): 545–559. doi:10.1002/gj.2649. ISSN 1099-1034.
{{cite journal}}: Invalid|ref=harv(help) - Shipton, Eric (1960). "Volcanic Activity on the Patagonian Ice Cap". The Geographical Journal. 126 (4): 389–396. doi:10.2307/1793373.
{{cite journal}}: Invalid|ref=harv(help)
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