EGU21-13502
https://doi.org/10.5194/egusphere-egu21-13502
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Towards a better understanding of the role of glacier retreat and permafrost degradation in triggering secondary lahars

Theresa Frimberger1, Daniel Andrade2, and Michael Krautblatter1
Theresa Frimberger et al.
  • 1Technichal University of Munich, Landslide Research Group, Munich, Germany (theresa.frimberger@tum.de)
  • 2Instituto Geofísico, Escuela Politécnica Nacional, Quito, Ecuador (dandrade@igepn.edu.ec)

As everywhere in the Andes, tropical glaciers have been rapidly retreating since several decades. The glaciers of Cotopaxi volcano, Ecuador, have been reduced in area by about 50% since 1976 (Cáceres, 2017). The Cotopaxi is mostly famous for its capacity to produce massive lahars during volcanic eruptions, but comparably smaller, secondary lahars generated in post-eruptive periods by heavy rainfall occur more frequently on the volcano’s flanks. However, since a few years, secondary lahars that originate in proglacial areas without any clear trigger mechanism are recorded at Cotopaxi. This raises the question of whether there exists a process-based link between the occurrence of secondary lahars and the retreat of cold-based glaciers with accompanied permafrost degradation in the former subglacial frozen pyroclastic material over the following years and decades.

Here, we present the data obtained from laboratory-calibrated Electrical Resistivity Tomography (ERT) and Seismic Refraction Tomography (SRT) conducted near the glacier margin between 5000 and 5300 m asl, which provide a better understanding of frozen/unfrozen conditions and the structure of the subsurface. In addition, data loggers have been recording surface air temperatures close to the glacier since May 2018. Our measurements show that permafrost cannot develop under current thermal conditions, but high electrical resistivities at depths of 10-20 m correspond to calibrated rock temperatures below 0 °C. The detected frozen lenses may act as detachment planes of periglacial secondary lahars in pyroclastic material recently exposed by glacier retreat.

 

Cáceres, B. (2017). Goal workshop 2017 Mexico 135 Evolución de los glaciares del Ecuador durante los últimos 60 años y su relación con el cambio climático. Conference paper: The role of Geosciences to societal development: A German-Latin American Perspective. GOAL Geo-Network of Latin American-German Alumini. P. 149. México: UANL-Monterrey-México.

How to cite: Frimberger, T., Andrade, D., and Krautblatter, M.: Towards a better understanding of the role of glacier retreat and permafrost degradation in triggering secondary lahars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13502, https://doi.org/10.5194/egusphere-egu21-13502, 2021.

Display materials

Display file

Comments on the display material

to access the discussion