HR: 10:50h
AN: V22A-03    [Abstracts]
TI: Evolution and hazards of an inactive compound shield volcano: Cofre de Perote (eastern Mexico)
AU: * Carrasco, G
EM: gerardoc@geociencias.unam.mx
AF: Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus UNAM Juriquilla, Carr. 15.5 Qro.-SLP, Queretaro, Qro 76230, Mexico
AU: Diaz, R
EM: rdiaz@geociencias.unam.mx
AF: Posgrado en Ciencias de la Tierra. Centro de Geociencias, Campus UNAM Juriquilla, Carr. 15.5 Qro.-SLP, Queretaro, QRO 76230, Mexico
AU: Siebert, L
EM: SIEBERTL@si.edu
AF: Smithsonian Institution, Global Volcanism Program, NHB-119, Washington, D.C 20013, United States
AU: Rodri­guez, J
EM: joseluisrv@hotmail.com
AF: Posgrado en Ciencias de la Tierra. Centro de Geociencias, Campus UNAM Juriquilla, Carr. 15.5 Qro.-SLP, Queretaro, QRO 76230, Mexico
AB: Cofre de Perote is located at the northernmost end of the Cofre de Perote-Citlaltépetl volcanic range that forms the eastern boundary of the Trans-Mexican Volcanic Belt. This range comprises an important physiographic feature separating the Gulf coastal plains from the Altiplano, with a difference in relief of more than 1,000 m causing regional unstable conditions that have favored sector collapse of the volcanoes towards the coast. In contrast to the typical stratovolcanoes of the Mexican Volcanic Belt, Cofre de Perote volcano is dominated by the emplacement of andesistic and dacitic lava flows with very minor proportions of pyroclastic deposits, which gives it the morphology of a shield volcano with gentle slopes. The lava flows erupted through different vents like a compound volcano instead of a single conduit. The summit area of Cofre de Perote volcano is characterized by a prominent set of scarps that as a group show a spectacular horseshoe shape that may be linked to repetitive flank failures. So far, at least two main debris avalanche deposits have been confirmed on the eastern lower slopes of Cofre de Perote towards the Gulf of Mexico. There are five major evolutionary stages that characterize the growth of this compound volcano including: 1) emplacement of a multiple vent dome complex that forms the basal structure of Cofre around 1.3-1.9 Ma; 2) construction of the lower structure of the Cofre compound volcano by at least two main upper vents at 400 ky; 3) building of the summit dome-like lavas through various vents at 240 ky; 4) A large number of Pleistocene-to- Holocene monogenetic cones, likely related to regional volcanism, were erupted through the flanks of the Cofre de Perote edifice; 5) long after the volcano ceased its activity, repetitive sector collapse events occurred causing the truncation of the original volcano shape at 40 and 10 ky. These events show that the upper parts of the volcanic edifice collapsed in the Late-Pleistocene-Holocene, apparently unrelated to any volcanic activity of the central edifice. Therefore, other triggers such as earthquake shaking or unusual heavy rainfall must be considered as the initiating cause.
DE: 8425 Effusive volcanism
DE: 8429 Lava rheology and morphology
DE: 8488 Volcanic hazards and risks
DE: 8499 General or miscellaneous
DE: 9605 Neogene
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly