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

Abstract

The morphological evolution of a volcano records the main events of its formation, and its complexity is a function of 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 are many exceptions to these general sequences. One exception is represented by Chimpa Volcano, an andesitic stratovolcano located in the Central Puna of the Andes. In order to evaluate the morphological evolution of Chimpa Volcano, 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 one destructive event have been recognized. The current morphology is related to the formation of an elongated depression flanked by scarps, named Quebrada Casana generated by a destructive event. Morphology and stratigraphy were linked using a parameter named emplacement balance (E*) which is defined as the volumetricratio between the volcanic products emplaced far away from the vent and those which remain near vent. Chimpa Volcano´s morphological evolution is directly related to the type of volcanic products emitted. The evolution began with the emission of pyroclastic density currents (PDCs), where E* remains high, favoring the development of a plateau (Stage I). Then lava dome emplacement in a central position and its destruction reduced the value 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 relation to their morphology can be applied to other volcanic edifices in the central Andes and elsewhere