Mission
The Cordillera Blanca, located between latitudes 8-10°S in Peru, is the most glaciated intertropical mountain range in the world (Masiokas et al., 2020), with numerous peaks above 6000m still holding several hundred glaciers. Particularly affected by current global warming, the area of those glaciers decreased by ~25% between 1962 and 2016 (Concha et al., 2019). This retreat of the cryosphere combined with permafrost degradation strongly increase the rate of natural hazards such as ice falls, glacial lake outburst flood (GLOFS), rock avalanches (e.g., Huggel et al., 2020) which generally occur in the highest reliefs, but often reach towns and villages in the lower valleys (rio Santa, Callejon de Huyalas, ~300,000 inhabitants). These hazards have been responsible for tens of thousands of casualties in this region since the 1950s (Carey, 2014), including some of the deadliest natural disasters of the last century: rock/ice avalanches initiated on the northern summit of Huascaran (6,768 m) carried several tens of millions of m3 of material and spread for tens of kilometers downstream, destroying many villages (Ranrahirca – 1962, Yungay – 1970, ~7,000 casualties for both events; Evans et al., 2009).
In this context, the aim of this project is to produce a « spatio-temporal » inventory of large (> Mm^3) rock-avalanches within the Cordillera Blanca to better assess their spatial distribution, to document their frequency of occurrence and magnitude, and to identify the periods and/or mechanisms favoring their triggering. Particular attention will be paid to the possible link between ancient avalanches and past climatic oscillations identified from over the last hundred thousand years (Concha et al., 2023). This work will be facilitated by the absence of glacial cover in the debris accumulation zones, favoring the preservation of gravitational morphologies over the long term and their detection through digital elevation model (DEM) analysis. Two sites have already been identified at the bottom of the Huascaran and Huandoy nevados (Yungay and Caraz: the sites of historic disasters), where the progressive accumulation of successive avalanche debris has produced debris cones extending over several tens of km². Preliminary field observations there led to the identification of numerous (multi-decametric) boulders that bear witness of events of greater magnitude/volume than historical avalanches.
An innovative and multi-disciplinary approach combining fieldwork, remote sensing, geochronology, and numerical modeling will be undertaken to characterize and to age these deposits. Several geochronological approaches (cosmogenic nuclides, OSL, 14C) will be combined with quantitative geomorphological analysis to characterize and age these deposits. High-resolution DEMs generated from SPOT and Pleiades satellite images will play a crucial role for this research. Indeed, the identification and mapping of rock-avalanche deposits will constitute the primary set of constrain for this PhD project. Additionally, we will compare recent satellite acquisitions with older satellite imagery (e.g., , Fekete, 2020) to assess volume differences among different events that have occurred over the past few decades.
The expected geomorphological archives reconstructed over longer period (10^3 to 10^5 years) will be compared with paleoclimatic reconstructions that are already well documented in the area for these periods (e.g., Thompson et al., 1995). Thus, it will be possible to identify the timing of occurrence of extreme avalanches and their potential link with past cryosphere fluctuations.
A major expected outcome is to understand the evolution of the Cordillera Blanca environment in the current context of glacial retreat and to characterize the triggering modes of low-frequency events (recurrence greater than 10^2 years) which is essential in the context of risk management for local populations. This study will document the characteristics of these rock-ice avalanches (thickness, volume, run-out/-up), which are key parameters for numerical modeling. Understanding the origin, mechanisms, and frequency of occurrence of these rock-ice avalanches in the Cordillera Blanca represents a real challenge for our Peruvian partners in charge of natural risk management in these densely populated valleys.
his PhD project will serve as a new basis of expertise for replication in other Peruvian cordilleras . The project is therefore strongly supported by our Peruvian partners (INGEMMET/INAIGEM), who will provide all the technical and material resources required for its completion, including 4×4 vehicles, mission funding, drone equipment and co-funding via Peruvian research-calls. This project is already co-funded (PhD 1/2-funding) by the PEPR IRIMA (priority exploratory research program and equipment for integrated risk management for more resilient societies in the era of global change) led by the CNRS, the BRGM and and the Grenoble Alpes University.
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For more Information about the topics and the co-financial partner (found by the lab !); contact Directeur de thèse – julien.carcaillet@univ-grenoble-alpes.fr