First geophysical exploration of periglacial landforms in southern Tierra del Fuego, Chile

Monitoring permafrost is of paramount importance due to its critical role as the foundation of soil mechanical and biological stability. Periglacial environments serve as valuable indicators of past and present climate conditions, offering unique insights into geomorphological processes and landscape evolution. However, degrading permafrost, driven by the warming climate, poses significant challenges. It affects soil hydrology and stability, alters carbon storage and release dynamics, and threatens ecosystems reliant on frozen ground. Furthermore, these changes have cascading effects on human infrastructure and contribute to feedback mechanisms that exacerbate global climate change.

There is no direct evidence for the presence of permafrost in southern Patagonia, apart from geomorphological processes. However, Tierra del Fuego (54°S), an archipelago shared by Argentina and Chile, is an extensive region where dozens of mountains exceed 1,500 m in elevation, and probabilistic maps of permafrost speculate that it may exist in elevated areas.

At the end of the austral summer 2024, a pioneering geophysical campaign was carried out in a remote area of the N-E Darwin Cordillera (54°S), without any assistance from vehicles or helicopters. We applied two of the most used and complementary geophysical techniques, i.e. Electrical Resistivity Tomography (ERT) and Seismic Refraction Tomography (SRT) with enough sensitivity to discretize either partially frozen ground or very shallow lenses of degrading permafrost profiles. The investigations were motivated by the expansion of the infrastructure network toward the southern national border and the encounter with the Darwin Range along the Beagle Channel, as the recent degradation of frozen soils could alter the compaction and settlement of the soil surface, leading to subsidence and frost heave. In particular, the road under construction involves reaching passes over the Cordillera, at whose elevations frozen ground is likely to be found.

In this work, we present a preliminary characterization of the periglacial environment in Yendegaia park, Tierra del Fuego. The use of electro-seismic geophysics, coupled with field observations and analysis, enabled to obtain more accurate subsoil models through a non-invasive approach. Validation by direct invasive techniques (i.e., soil coring) was unfortunately not possible at that moment, due to logistic complications and costs. The geophysical results obtained, coupled with the geomorphological slope processes observed, suggest the presence of frozen ground, active-state mountain periglacial processes and potentially permafrost around its probability limits in Tierra del Fuego, above 650 m a.s.l., becoming essential information at both geotechnical and climatic levels.