Spatio-temporal evolution of distributed volcanic fields, case studies—Sierra Chichinautzin and Michoacán-Guanajuato, México
An analysis of 1,375 volcanoes in the Michoacán-Guanajuato (1,148 volcanoes in a 26,200 square-kilometer area) and Sierra Chichinautzin (227 volcanoes in a 3,500 square-kilometer area) volcanic fields in central Mexico identified patterns in the spatial and temporal distribution of past eruptions. A cluster agglomerative hierarchical method and kernel analysis confirmed that the Michoacán-Guanajuato volcanic field comprises four volcanic fields (Valle de Santiago, Uruapan, Apatzingán, and Pátzcuaro volcanic fields) controlled by different fault systems, indicating that it is not a single volcanic field but rather a group of volcanic fields (a “superfield”), each of which has distinct characteristics. In the Sierra Chichinautzin volcanic field, well-constrained isotopic ages were used to build a model of how the spatial distribution of the eruptions has changed over time. Two new 40 Ar/ 39 Ar ages from a locally recognized volcanic feature near the town of El Cantil, herein called El Cantil volcano (1,537±17 kilo-annum [ka]) and the volcanic feature at Cerro el Elefante (herein called El Elefante dome) (1,485±92 ka) belong to the oldest volcanic group identified in the Sierra Chichinautzin volcanic field, confirming the timing of the beginning of monogenetic volcanism in the region. Based on the volcanic groups identified in the Sierra Chichinautzin volcanic field, the youngest volcanism (less than 35 ka) is found only in the central-western sector of the field. Principal component analysis determined the directional trends of feeder dikes only for vents <10 ka in the Sierra Chichinautzin volcanic field. Possible magma migration paths through the crust were identified using seismic data from both volcanic fields using an earthquake catalog from 1973 to 2023, which includes 9,016 earthquakes in the Michoacán-Guanajuato volcanic field and 841 in the Sierra Chichinautzin volcanic field. The spatial distribution of the hypocenters does not highlight any trend that could be associated with superficial movement of magma in the Sierra Chichinautzin volcanic field. In the Michoacán-Guanajuato volcanic field, however, eight seismic swarms since 1997 have been detected. These swarms are interpreted to result from ascending magma. Strengthening monitoring systems and reinforcing mitigation measures to address volcanic hazards and risk are important means of preparing for future eruptions in both regions. Analysis such as those herein provide insights as to where an eruption might occur and may help mitigate volcanic hazards.