Thesis supervision

Long-term frequency of rockfall/rock avalanche by multidisciplinary surface exposure dating in the Mont Blanc massif.

The objective of the MB-RED project is to establish a global model to characterize the dynamics of rockfalls at high altitude during the last glacial-interglacial cycle. The works concerning recent periods (the last century) show an increase in rockfalls in the Mont Blanc massif. Their frequency suggests a causal relationship with climate change. The aim of our study is to identify periods of strong gravitational activity since the LGM in order to verify the observations made since the last century.
In order to have sufficient data to allow a reasonnable statistic, it is necessary to develop a semi-quantitative dating protocol. Our challenge is to develop an approach based on the physico-chemical evolution of the varnish of the scars which, evolving under the action of external agents (water, temperature, biological activity, wind) should be influenced by the exposure time.
For this purpose, we combine TCN dating of scars with contrasting coloured surfaces and multi-modal analysis of the surface color (colorimetric spectra, geochemical assessment, biological characterization). The objective is to propose a relationship between the age of exposure to TCN and the physico-chemical properties of rock surfaces.
This would then enable us to map the "history of rockfall" on the scale of a massif, Mont Blanc, using high-resolution images of the walls.

Thesis : Xavi Gallach. THESIS DEFENDED LE 12 OCTOBER 2018
Co-supervision : J.Carcaillet (ISTerre), Ph. Deline et L. Ravanel (EDYTEM)
Funding : AGIR-POLE Univ. Grenoble Alpes. ANR VIP Mont Blanc

Quaternary glacial dynamics of the Andean region of Merida (Venezuela).

The objective of the thesis is to specify the chronology of the glacier retreat in the Andes of Merida (Western Venezuela). Unlike the Andes Cordillera, this 400 km long and 5000 m high massif remains little studied despite the presence of very well preserved glacial morphologies. However, geormophological investigations indicate that the glacial cover has decreased from 600 km2 during the last glacial maximum to less than 3 km2 today. The few available data have been too weak to allow an accurate reconstruction of the response of tropical glaciers to post-glacial change.
The pilot campaign carried out in the Mucubaji Pass sector indicates that deglaciation was rapid (< 8 ka for a total retreat between 3100 and 4500 m) and seems to suggest that the pass acted as a clear climatic barrier (the wet northern sector linked to the oceanic entrances and the drier southern sector). To progress and validate these first results, the 2013 sampling concerned a valley located in the southern sector (Culata and Gavidia Valley).

Thesis : Isandra Angel. THESE DEFENDED THE 12 FEBVRIER 2016
Co-supervision : J.Carcaillet (ISTerre), F. Audemard (CUV, Caracas, Venezuela)
Funding : IRD, ECOS-Nord, BQR