Ceboruco

Ceboruco
height	2280  m
location	State of Nayarit , Mexico
Coordinates	21 ° 7 ′ 30 ″  N , 104 ° 30 ′ 30 ″  W Coordinates: 21 ° 7 ′ 30 ″  N , 104 ° 30 ′ 30 ″  W
Type	Stratovolcano
rock	Andesite , dacite
Age of the rock	Middle Pleistocene, Late Pleistocene, Holocene
Last eruption	1870-1872

The Ceboruco is located in Nayarit , 2280 meters high andesitic - Dacite stratovolcano of the Sierra Volcánica Transversal . The eruption of the year 1005, with 10.7 cubic kilometers of tephra, is one of the 50 largest eruptions of the Holocene .

etymology

The Ceboruco was originally called Tonan in Nahuatl, meaning a light as bright as the sun . The Spanish word ceboruco generally refers to a difficult terrain to traverse, such as Aa currents, and is found, for example, in the Canary Islands . It has the same meaning as vericueto - rough terrain with obstacles that are difficult to pass .

description

The Ceboruco has a volume of 51 + 2.5 cubic kilometers and in its summit area consists of a large caldera with a diameter of 3.7 kilometers, which was formed during the Jala eruption . The Dos Equis lava dome then formed in it , which in turn collapsed during the Copales eruption, leaving a caldera 1.5 kilometers in diameter. Within these two craters there are several explosive volcanic structures such as lava domes, pyroclastic domes and ash cones associated with scoria deposits.

In its pre-caldera stage, the stratovolcano produced 38 cubic kilometers of rock, 90% andesite and 10% dazite. The explosive Jala eruption was of a Dazite nature and its volume was 3 to 4 cubic kilometers. The postcaldera stage has a total of 9 eruptions with a volume of 9.5 cubic kilometers, 5.15 cubic kilometers being andesite and 4.35 cubic kilometers being dazite.

geology

Located northwest of Guadalajara , Ceboruco belongs to the Ceboruco-San-Pedro volcanic field in Nayarit and is located in the western part of the Sierra Volcánica Transversal. After the Colima, it is the second most active volcano in the volcanic arc of the Sierra Volcánica Transversal, which was created by subduction of the Rivera Plate and the Cocos Plate under the North American Plate . The 9-million-year-old Rivera microplate subducts at an average speed of 2.3 centimeters / year at a rather steep dip angle of 50 ° to the northeast and is suspected below the Ceboruco at a depth of 200 to a maximum of 320 kilometers. Because of its proximity to the Rivera ridge , the northern continuation of the East Pacific Ridge , the microplate is younger and warmer in the west and therefore subducts more slowly (1.9 ± 0.3 cm / year) than in the east (3.8 ± 0.4 cm / year ).

The much older coconut plate (12 to 18 million years old) subducts in a north-northeast direction at 3.8 centimeters / year at a smaller angle of incidence of 30 ° (at its western edge with the Rivera plate). Your angle of incidence flattens out towards the east and merges completely into the horizontal south-east below Mexico City .

The 1600 square kilometer Ceboruco-San Pedro volcanic field with more than 70 volcanic vents is located in the Tepic-Zacoalco Trench (more precisely a half-trench with a Listrian marginal fault on its northwestern side), the northwest-trending section of a Cenozoic triple-trench system with a center nearby from Guadalajara. In terms of volume, the Tepic-Zacoalco Trench is dominated by five andesitic-Dazitic stratovolcanoes (60 cubic kilometers each) and two peralkaline rhyolite centers (40 cubic kilometers each) ( San Juan , Los Navajos , Sangangüey , Tepetiltic , Ceboruco, Tequila and Sierra la ) . The stratovolcanoes are accompanied by numerous monogenetic ash cones with an affinity to oceanic island basalts (OIB), which line up along northwest-southeast trending faults . The Ceboruco alone is accompanied by 13 such monogenic ash cones. Also worth mentioning are more than 20 andesitic and Dacite lava domes west of the Ceboruco, including their largest, the Dacite San Pedro lava dome with the stratovolcano of the Tepetiltic as a northern neighbor.

At the triple point, the Ceboruco-San-Pedro volcanic field changes its direction to the east and forms the Chapala Trench here . The north-south trending Colima rift segment extending from the triple point contains only a single central volcanic complex, the Colima- Nevado de Colima, the volume of which is estimated at 450 cubic kilometers and therefore the volcanoes of the Tepic-Zocoalco rift by almost an order of magnitude surpasses.

The crust segment framed by the two Triple Trenches and the Central America Trench forms the Jalisco Block . The Jalisco Block is underlain by a Cretaceous , 100 to 75 million year old granite batholite , most of which was excavated before the Pliocene and whose upward movement is likely to continue even today. Northeast of the Tepic-Zacoalco Trench is the North American Plate with the volcanic rocks of the Sierra Madre Occidental (SMO). The Sierra Madre Occidental is one of the most extensive rocky magma provinces on earth and is composed mainly of Ignimbrites. These ignimbrites can also be found in the Tepic-Zacoalco Trench (where they lie over chalk rocks), but are missing in the Jalisco block further southwest.

Formation and outbreaks

The volcanic building of Ceboruco sits on tertiary ignimbrites . Its initial phase was of a purely effusive nature - andesitic lava flows built a stratovolcano, which with a volume of 46 to 48 cubic kilometers should have reached a height of around 2700 meters. The beginning of volcanic activities is dated by Ferrari and colleagues (1997) to 320,000 years BP, whereby this information is subject to a very high error of 200,000 years. The andesites were then penetrated by a system of veins that could be dated to around 45,000 ± 8,000 years BP . The initial phase of the volcano is therefore older than 45,000 years. The volcano then entered a longer period of rest, as evidenced by clear erosion channels on its flanks. Towards the end of this dormant phase, the volcano resumed its activity and released the Destiladero lava flow from a crack on the north flank .

The Plinian , trachydacite Jala eruption with a VEI of 6 from the year AD 1005 (± 15 years) was undoubtedly the strongest eruption on Ceboruco. It immediately followed the Destiladero lava flow and hurled 10.7 cubic kilometers of tephra (corresponding to 3 to 4 cubic kilometers DRE ) into the atmosphere in an eruption column , from which an ejection layer more than 50 centimeters thick, drifting northeast, fell over 560 square kilometers. Pyroclastics drifted to the southwest as glowing clouds, where they formed the Marquesado pyroclastic current.

After the Jala eruption, the volcano remained very active and left six more lava flows before the Spanish arrived in 1521: Copales, El Cajón, Coapan I, Coapan II, El Norte and Ceboruco . The activities continued until the next major eruption in 1870, but were mainly limited to the caldera area. The eruption from 1870–1872 lasted until 1875 and fumaroles were observed into the 20th century. Even today, smaller fumaroles can be seen in the summit area.

composition

The lavas that emerged from the volcano are calcareous and primarily trachyandesic in composition, with the andesitic lavas taking on an increasingly clear trachydacite character over time. The magma is thought to originate from three different source regions with rhyodacite, Dacite and mafic composition. The Dacitic source magma is in turn a mixture of a rhyodacite and a basaltic component.

mineralogy

The andesites of the first phase are porphyry (with 30 to 45 volume percent phenocrystals ) and of a fairly homogeneous composition. As phenocrystals they have plagioclase and hypersthene , occasionally also augite and olivine . Microliths of plagioclase, hypersthene and titanomagnetite swim in the glassy matrix .

Main elements

Oxide wt.%	Andesite initial phase	Jala eruption	Andesite postcaldera stage	Eruption from 1870
SiO 2	58.50	68.37	60.53	67.85
TiO 2	0.97	0.30	1.24	0.63
Al 2 O 3	17.85	15.40	16.69	15.30
FeO dead	5.55	2.09	5.78	3.50
MnO	0.11	0.10	0.13	0.08
MgO	2.75	0.37	2.34	0.69
CaO	6.22	1.51	5.24	2.11
Na 2 O	4.93	5.30	4.63	5.22
K 2 O	1.80	3.22	2.13	3.53
P 2 O 5	0.22	0.09	0.37	0.13

The explosive Jala eruption of AD 1005 and also the eruption of 1870 clearly differ in their chemism from the generally effusive andesites (significantly higher SiO ₂ content, higher Na + K, but lower CaO, P ₂ O ₅ , TiO ₂ , MgO and FeO).

Individual evidence

1. ^ Razo-Zaragoza, JL: Conquista hispánica de las provincias de los Tebles Chicimecas de la America Septentrional . Ed. Universidad de Guadalajara, 1988, p. 97 .
2. ↑ Sieron, K. and Siebe, C .: Revised stratigraphy and eruption rates of Ceboruco stratovolcano and surrounding monogenetic vents (Nayarit, Mexico) from historical documents and new radiocarbon dates . In: Journal of Volcanology and Geothermal Research . tape 176 , 2008, p. 241-264 , doi : 10.1016 / j.jvolgeores.2008.04.006 .
3. ↑ ^{a b} Frey, HM, Lange, RA, Hall, CM and Delgado-Granados, H .: Magma eruption rates constrained by ⁴⁰ Ar / ³⁹ Ar chronology and GIS for the Ceboruco-San Pedro volcanic field, western Mexico . In: GSA Bulletin . tape 116 , no. 3/4 , 2004, p. 259-276 , doi : 10.1130 / B25321.1 .
4. ↑ Klitgord, KD and Mammerickx, J .: Northern East Pacific Rise — Magnetic anomaly and bathymetric framework . In: Journal of Geophysical Research . tape 87 , 1982, pp. 6725-6783 .
5. ^ Pardo, M. and Suarez, G .: Shape of the subducted Rivera and Cocos plates in southern Mexico — Seismic and tectonic implications . In: Journal of Geophysical Research . tape 100 , 1995, pp. 12.357-12.373 .
6. ↑ Luhr, JF, Nelson, SA, Allan, JF and Carmichael, ISE: Active rifting in southwestern Mexico - Manifestations of an incipient eastward spreadingridge jump . In: Geology . tape 13 , 1985, pp. 54-57 .
7. ↑ Allan, JF, Nelson, SA, Luhr, JF, Carmichael, ISE, Wopat, M. and Wallace, PJ: Pliocene – Holocene rifting and associated volcanism in southwest Mexico: An exotic terrane in the making, in The Gulf and Peninsular province of the Californias . In: American Association of Petroleum Geologists Memoir . tape 47 , 1991, pp. 425-445 .
8. ↑ Allan, JF: Geology of northern Colima and Zacoalco grabens, southwest Mexico: Late Cenozoic rifting in the Mexican Volcanic Belt . In: Geol. Soc. At the. Bull. Band 97 , 1986, pp. 473-485 .
9. ^ Luhr, JF and Carmichael, ISE: The Colima Volcanic Complex, Mexico: Part 2. Late Quaternary cinder cones . In: Contributions to Mineralogy and Petrology . tape 76 , 1981, pp. 127-147 .
10. ↑ Ramírez-Herrera, MT, Kostoglodov, V. and Urrutia-Fucugauchi, J .: Overview of recent coastal tectonic deformation in the Mexican Subduction Zone . In: Pure and Applied Geophysics . tape 168 , 2011, p. 1415-1433 , doi : 10.1007 / s00024-010-0205-y .
11. ^ Ferrari, L., Nelson, SA, Rosas-Elguera, J., AguirreDiaz, GJ and Venegas-Salgado, S .: Tectonics and volcanism of the Western Mexican Volcanic Belt. Magmatism and tectonics in central and northwestern Mexico — a selection of the 1997. IAVCEI General Assembly Excursions . In: Aguirre-Diaz, GJ, Aranda-Gomez, JJ, Carrasco-Nuñez, G. and Ferrari, L. (Eds.): Excursion . tape 12 . Mexico DF, Universidad Nacional Autonoma de Mexico, Instituto de Geología 1997, p. 85-129 .
12. ↑ Chertkoff, DG and Gardner, JE: Nature and timing of magma interactions before, during and after the caldera-forming eruption of Volcan Ceboruco, Mexico . In: Mineral Petrol. tape 146 , 2003, p. 715-735 .
13. ↑ Nelson, Stephen A .: Geología del Volcán Ceboruco, Nayarit, con una estimacion de risgos de erupciones futuras . In: Univ. Nal. Autón. Inst. Geología, Revista . Vol. 6, No. 2 , 1986, p. 243-258 .