Morphological analysis of Lautaro volcano, Austral Volcanic Zone of the Andes: Insights into the evolution of an active volcano in the Southern Patagonian Ice Field

Abstract

The Lautaro volcano is the northernmost and highest volcanic center of the Austral Volcanic Zone (AVZ) of the Andes. It is in the northwestern part of the plateau of the Southern Patagonian Ice Field along the northern continuity of the Pío XI chain. The volcano is almost entirely ice-covered, nourishes numerous large outlet glaciers, and has been the object of only very limited field-based geological studies. The volcano is a key location within the Southern Patagonian Ice Field due to its potential influence on the advancement trend cycles of the Pío XI glacier. The present contribution uses the Red Relief Image Map technique to identify volcanic landforms and structures in a glacial context, providing the first quantitative morphological assessment of the Lautaro volcano. The results show plateau-like lava flows at the base of the volcano, possibly concentrically emplaced from a single emission center during the first stages of volcano construction. Subsequent stages comprise two main edifices formed by overlapped lavas and coulées on top, with multiple emission centers aligned along a NE-SW volcanic lineament. The early evolution of the volcano seems to have been influenced by the regional paleotopography. The approximate pre-eruptive surface is relatively flat, with a depression in the northern and eastern sectors of the volcano and a positive relief towards the southern and western parts. Furthermore, a review of the historical activity and tephra records from lakes in Argentina was performed to reassess the eruptive activity of Lautaro. This review reveals a cycle of intermittent historical volcanic activity, with at least three major eruptions during the 1870s and 1880s, and classifies Lautaro as the most active volcanic center in the AVZ, at least since the late 19th century. These antecedents advance our knowledge about the interactions between volcanoes and glaciers in southern Patagonia, providing new perspectives on the evolution of this remote, ice-capped volcano.