Quaternary sector collapses of Nevado de Toluca volcano (Mexico) governed by regional tectonics and volcanic evolution

Nevado de Toluca volcano is an andesiticdacitic composite volcano of Late Pliocene-Holocene age located in the central-eastern sector of the Trans-Mexican Volcanic Belt, an active continental arc. The latest stage of Nevado de Toluca evolution, in the past 50 k.y., has shown an interplay between volcanic activity and kinematics of the basement structures. Geological mapping, stratigraphic analysis, morphological and structural interpretation, and analogue modeling were used to investigate these complex volcano-tectonics relationships. In the past 50 k.y., Nevado de Toluca volcano underwent at least three sector collapses on the east, east-southeast, and west flanks because of faulting and destabilization of young dacitic domes at its summit. Field and remotely sensed data supported by analogue models of transtensive basement tectonics revealed that these catastrophic events were strongly correlated to the presence of the east-west-striking active Tenango fault system. The geometry, kinematics, and dynamics of the basement structure controlled the growth of a dome complex in the volcano summit and its destabilization. As a consequence of the active basement tectonics, the most probable sector collapse directions in the case of future gravitational failures of the volcano summit will be east-southeast, west-northwest, east, and west. Nevado de Toluca poses potential hazards to more than 25 million inhabitants; the analysis presented in this paper can improve hazard mitigation on the basis of better knowledge of growth and collapse mechanism of the volcano. The numerous examples of composite volcanoes in continental and island volcanic arcs with similar structural-volcanological characteristics of Nevado de Toluca volcano imply that the model results can also act as a guide to study the growth and collapse of other composite volcanoes affected by basement structures. © 2007 Geological Society of America.