Unusual volcanic instability and sector collapse configuration at Chimpa volcano, central Andes

NORINI, GIANLUCA; BUSTOS, EMILCE; ARNOSIO, MARCELO; BAEZ, WALTER; ZULUAGA, MARIA CLARA; ROVERATO, MATTEO

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH

ELSEVIER SCIENCE BV

Año: 2020 vol. 393

0377-0273

UpperMiocene Chimpa volcano is one of the largest stratovolcanoes of the back?arc region of the central Andes.The gentle?sloped volcano underwent previously unrecognized volcanic instability, consisting of≈2 km3 mass?wasting processes and catastrophic sector collapse, whose characteristics have been identified by means of stratigraphy,geological mapping and structural analysis. The origin of instability at Chimpa can be attributed to tectonicfaulting, hydrothermal alteration and overloading. These common promoting and triggering factors haveproduced an unusual configuration of the volcano gravitational instability, characterized by parallel landslidescars delimiting unstable sectors on eastern and western volcano flanks,with large toreva blocks sliding in oppositedirections, perpendicular to the flow direction of a subsequent long?run out debris avalanche. Even if thestyle of such a complex volcanic instability has never been described before, its identification may be also usefulto study volcano sector failures and mass?wasting deposits in other volcanoes worldwide.