Geomorphological evolution of the Chimpa stratovolcano in the back-arc region of the Central Andes

BUSTOS, EMILCE; ARNOSIO, MARCELO; BÁEZ, WALTER; NORINI, GIANLUCA; SUZAÑO, NÉSTOR OMAR; VIRAMONTE, JOSÉ GERMÁN

GEOMORPHOLOGY

ELSEVIER SCIENCE BV

Año: 2020 vol. 364

0169-555X

The morphological evolution of a volcano records the main events of its formation, and its complexity is a functionof overlapping constructive and destructive phases. Typical morphological evolutionary trends have beenestablished: simple cones grow into larger cones or they widen into sub-cones or massifs. However, there aremany exceptions to these general sequences. One exception is represented by Chimpa Volcano, an andesitic stratovolcanolocated in the Central Puna of the Andes. In order to evaluate the morphological evolution of ChimpaVolcano, its morphology was characterized, analyzed and quantified using a Digital Elevation Model (DEM).Chimpa Volcano is morphologically classified as a sub-cone, and three constructive stages of evolution and onedestructive event have been recognized. The current morphology is related to the formation of an elongated depressionflanked by scarps, named Quebrada Casana generated by a destructive event. Morphology and stratigraphywere linked using a parameter named emplacement balance (E*) which is defined as the volumetricratio between the volcanic productsemplaced far away fromthe vent and those which remain near vent. ChimpaVolcano's morphological evolution is directly related to the type of volcanic products emitted. The evolutionbegan with the emission of pyroclastic density currents (PDCs), where E* remains high, favoring the developmentof a plateau (Stage I). Then lava dome emplacement in a central position and its destruction reduced thevalue of E* and a massif was created (Stage II). Finally E* reached the lowest value when the volcano began toemit lava flows forming a sub-cone (Stage III). The presented methodology to evaluate volcanic products in relationto their morphology can be applied to other volcanic edifices in the central Andes and elsewhere.