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New stratigraphic and structural data obtained during recent geological surveys have allowed us to subdivide the almost continuous evolution of Etnean volcanism into four main phases. The oldest phase (Basal Tholeiitic) corresponds to a long period of dispersed fissuretype volcanism with tholeiitic affinity, from about 580 up to 260 ka. This phase represents the northward extension of the Plio-Pleistocene Hyblean volcanism to the Etnean region. The second phase (Timpe) started about 220 ka when eruptive activity was mainly concentrated on the Ionian coast along the NNW-SSE oriented Timpe fault system. In this area the occur rence of fissure-type eruptions formed a small shield volcano and the passage between tholeiitic to alkaline volcanics occurred. The third phase (Valle del Bove Centers) is marked by a main westward shift of the feeding system in the Valle del Bove (VdB) area forming some nested volcanic centers. The earliest volcanic edifices recognized are Tarderia and Rocche. Afterward the volcanism was mainly concentrated on the southwestern side of the VdB with the formation of Trifoglietto volcano. Local shifting of the feeder caused the for mation of three different volcanic centers: Giannicola, Salifizio and Cuvigghiuni. Finally, in the fourth phase (Stratovolcano) the definitive stabilization of the plumbing system led to the construction of the main stratovolcano, Ellittico, which forms the bulk of the present edifice. Four caldera-forming Plinian eruptions, occurring at about 15 ka, marked the end of Ellittico activity. During the Holocene, persistent basaltic volcanic activity formed the Mongibello volcano, whose products cover at least 85% of the Mount Etna area.

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[1] The Colima Volcanic Complex (CVC) is currently the most active Mexican volcano and is located in the western sector of the Trans-Mexican Volcanic Belt, inside the active Colima Rift, a regional N-S-striking extensional structure. The Colima Rift is filled by a ∼1 km-thick sequence of quaternary lacustrine sediments, alluvium, and colluvium, mostly underling the about 3000-m-thick volcanic pile of the CVC. In this work we present the results of a detailed morphostructural and field study of Quaternary faults and fractures in the CVC and the surrounding area, including the regional structures of the Colima Rift. We also present a geometrical modeling of the faults inside the volcano and a numerical model of the gravity-induced stress and strain fields of the CVC. The study attempts to characterize the geometry, kinematics, and dynamics of the deformation features of the CVC and relate it with the volcano structure, the geology of the substratum, and the geodynamic setting of the region. Our model considers that the observed deformation of the CVC and the surroundings results from the interplay between the active N-S-trending regional extensional tectonics and the southward spreading of the volcano over its basement forming an E-W-oriented volcanotectonic graben. The interaction between regional tectonics and previously unrecognized volcanic spreading can control magma migration and flank instability, in an area where eruptions and sector failures represent a potential high risk for more than 500,000 people.

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Abstract:We study land subsidence processes and the associated ground fissuring, affecting an active graben filled by thick unconsolidated deposits by means of InSAR techniques and fieldwork. On 21 September 2012, Ciudad Guzmán (Jalisco, Mexico) was struck by ground fissures of about 1.5 km of length, causing the deformation of the roads and the propagation of fissures in adjacent buildings. The field survey showed that fissures alignment is coincident with the escarpments produced on 19 September 1985, when a strong earthquake with magnitude 8.1 struck central Mexico. In order to detect and map the spatio-temporal features of the processes that led to the 2012 ground fissures, we applied InSAR multitemporal techniques to process ENVISAT-ASAR and RADARSAT-2 satellite SAR images acquired between 2003 and 2012. We detect up to 20 mm/year of subsidence of the northwestern part of Ciudad Guzmán. These incremental movements are consistent with the OPEN ACCESS Remote Sens. 2015, 7 8611 ground fissures observed in 2012. Based on interferometric results, field data and 2D numerical model, we suggest that ground deformations and fissuring are due to the presence of areal subsidence correlated with variable sediment thickness and differential compaction, partly driven by the exploitation of the aquifers and controlled by the distribution and position of buried faults.

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