We model the submarine emplacement of a debris avalanche generated by the last flank-collapse event of Montagne Pel¿e volcano. We estimate the collapsed volume (1.7 km3) using both the volume of the missing material in the horseshoe-shaped structure and the volume of submarine deposits. This avalanche is treated as the gravitational flow of a homogeneous continuum. It is simulated by a finite-difference model, solving mass and momentum conservation equations, that are depth-averaged over the slide thickness. Numerical simulations show that the emplacement of this debris-avalanche can be suitably modeled by a Coulomb-type friction law with a variable friction angle below 10¿. We propose that variations of the friction angle are mainly influenced by the thickness of the flowing mass.