HR: 0800h
AN: V51A-08    [Abstracts]
TI: Revisiting Jorullo volcano (Mexico): monogenetic or polygenetic volcano?
AU: * Delgado Granados, H
EM: hugo@tonatiuh.igeofcu.unam.mx
AF: Instituto de Geofísica, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México, DF 04510, Mexico
AU: Roberge, J
EM: roberge@geofisica.unam.mx
AF: Instituto de Geofísica, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México, DF 04510, Mexico
AU: Farraz Montes, I A
EM: abimelec@servidor.unam.mx
AF: Instituto de Geofísica, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México, DF 04510, Mexico
AU: Victoria Morales, A
EM: victoria@servidor.unam.mx
AF: Facultad de Ingeniería, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México, DF 04510, Mexico
AU: Pérez Bustamante, J C
EM: jcperezb@pep.pemex.com
AF: Facultad de Ingeniería, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México, DF 04510, Mexico
AU: Correa Olan, J C
EM: jcorreaolan@yahoo.com.mx
AF: Facultad de Ingeniería, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México, DF 04510, Mexico
AU: Gutiérrez Jiménez, A J
EM: aaron joseph gutierrez jimenez lespaulmx@hotmail.com
AF: Facultad de Ingeniería, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México, DF 04510, Mexico
AU: Adán González, N
EM: nayeli adan karime1006@yahoo.com.mx
AF: Facultad de Ingeniería, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México, DF 04510, Mexico
AU: Bravo Cardona, E F
EM: edarz@correo.unam.mx
AF: Facultad de Ingeniería, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, México, DF 04510, Mexico
AB: Jorullo volcano is located near the volcanic front of the westernmost part of the Trans-Mexican Volcanic Belt, which is related to the subduction of the Cocos plate beneath the North American plate. This part of the TMVB is known as the Michoacán-Guanajuato Volcanic Field, a region where widespread monogenetic volcanism is present although polygenetic volcanism is also recognized (i. e. Tancítaro volcano; Ownby et al., 2006). Jorullo volcano was born in the middle of crop fields. During its birth several lava flows were emitted and several cones were constructed. The main cone is the Jorullo proper, but there is a smaller cone on the north (Volcán del Norte), and three smaller cones aligned N-S on the south (Unnamed cone, UC; Volcán de Enmedio, VE; and Volcán del Sur, VS). The cone of Jorullo volcano is made up of tephra and lava flows erupted from the crater. The three southern cones show very interesting histories not described previously. VE erupted highly vesiculated tephras including xenoliths from the granitic basement. VS is made of spatter and bombs. A very well preserved hummocky morphology reveals that VE and VS collapsed towards the west. After the collapses, phreatomagmatic activity took place at the UC blanketing VE, VS and the southern flank of the Jorullo cone with sticky surge deposits. The excellent study by Luhr and Carmichael (1985) indicates that during the course of the eruption, lavas evolved from primitive basalt to basaltic andesite, although explosive products show a reverse evolution pattern (Johnson et al., 2006). We mapped lava flows not described by the observers in the 18th century nor considered in previous geologic reports as part of the Jorullo lavas. These lavas are older, distributed to the west and south, and some of them resemble the lava flows from La Pilita volcano, a cone older than Jorullo (Luhr and Carmichael, 1985). These lava flows were not considered before because they were not extruded during the 1759-1774 eruption. Therefore, in spite of the long-standing idea of Jorullo being a monogenetic volcano, we hypothesize it as a stratovolcano in the making. The polygenetic nature of the volcano and the processes described here for Jorullo volcano (cone collapse, phreatomagmatic activity) are of great importance because of their implications for hazards assessment.
DE: 8404 Volcanoclastic deposits
DE: 8425 Effusive volcanism
DE: 8428 Explosive volcanism
DE: 8486 Field relationships (1090, 3690)
DE: 8488 Volcanic hazards and risks
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly