Geomorphological responses of periglacial environments to large scale mining activity in the Central Andes of Chile

We have investigated the present-day geomorphological dynamics induced by large scale open-pit mining in a periglacial environment of the Chilean Semiarid Andes. High resolution imagery (from Pléiades constellation) spanning a time interval of the last 10 years and additional historical aerial photographs provide valuables insights into spatio-temporal changes occurring in the Andina-Los Bronces copper mining complex. From two sub-catchments that display severe anthropic impacts, this study is focused on the long-term effects of the loading and unloading of mine waste on rock glacier evolution. This analysis is based on (i) geomorphological mapping, (ii) surface velocity fields extracted using an image correlation algorithm and (iii) surface elevation changes by DEM (Digital Elevation Models) differencing. On the two selected catchments, we present a unique classification of landforms reflecting the degree of mining alteration, based on their morphology and on the definition of an Index of Surface Disturbance (ISD). The main results highlight major signs of slope destabilisation caused by the removal of accumulated waste rock from mining processes. The long-term overloading of landforms currently results in their ongoing thinning and continuous motion towards the excavated area. We propose a conceptual explanation of their dynamics in agreement with the observed morphology, triggered by the overloading of the rock glaciers and concurrent with the genesis of creeping anthropogenic permafrost related features.