###### Abstract
This approach allows us to identify triggering conditions, especially the roles of permafrost degradation and glacial retreat--both consequences of the current global warming, which is particularly accelerated in mountainous regions. Furthermore, these events offer insights into runout dynamics [12], notably the effects of supra-glacial pathways on flow patterns [18]. Lastly, comprehending the post-event evolution of scars [19] and documenting changes in deposits and induced impacts on torrential activity are crucial [20]. Surprisingly, these aspects have received relatively little research attention to date. The Taconmaz glacier and valley in the Mont-Blanc massif (MBM, western European Alps) is a major risk site in the Alps with numerous large-scale snow avalanches over the last century [21; 22], often triggered by falling seracs from a large cold-based hanging glacier [23] whose stability with global warming is a cause for concern [24]. A new, multi-risk perspective emerged with the event of 24 November 2018, when a rockfall from the 2859 m a.s.l. Taconmaz spur triggered a mixed rock/ice avalanche that travelled down 1.85 km before stopping 165 m away from the construction site of a micro-hydroelectric power station. Approaching 5 \(\times\) 10\({}^{4}\) m\({}^{3}\), the event is one of the largest in MBM in recent decades, along with the collapse of Brenva spur on 18 January 1997 (2 \(\times\) 10\({}^{6}\) m\({}^{3}\)) [18], Drus on 29-30 June 2005 (0.3 \(\times\) 10\({}^{6}\) m\({}^{3}\)) [25], Aiguille de Tre-la-Tete on 10-11 September 2008 (5 \(\times\) 10\({}^{4}\) m\({}^{3}\)) [26], Tournier spur on the north face of Aiguille du Midi on 29 September 2017 (4 \(\times\) 10\({}^{4}\) m\({}^{3}\)), and the Trident du Tacul on 4 October 2018 (4 \(\times\) 10\({}^{4}\) m\({}^{3}\)). The last three events were observed and documented by a network of rockfall observers in the MBM [27]. A few kilometres to the south of the MBM, the collapse of the north face of Mont Crammont on 24 December 2008 (0.5 \(\times\) 10\({}^{6}\) m\({}^{3}\)) [28] originated at 2653 m a.s.l., i.e., considerably lower than all those mentioned directly above. The little rock avalanche crossed a plateau between 2050 and 2150 m a.s.l., where it deposited the bulk of the rock mass, and a small part of the mass continued downstream, forming two branches channelled by the torrents of Arpettaz and Planey. Vertical and horizontal travel distances were 1560 and 3050 m [28]. At a time when the relationship between climate change and geomorphological processes at high elevations is becoming increasingly important (Section 2), this study looks at the conditions that triggered the little rock/ice avalanche at Taconmaz basin (Section 3)--significant in terms of volume for the north-western side of the MBM, its extent and its proximity to issues--which occurred in November 2018 (Section 4), by analysing the triggering conditions and questioning a possible periglacial and/or paraglacial origin (Section 5). It also looks at the rock/ice avalanche runout using a numerical flow model based on depth-averaged equations and a Voellmy rheology with cohesion, the evolution of the scar and the rock/ice deposit obliterated by several snow avalanches, the dismantling of the deposit and the return of the volume to the Taconnaz torrent (Section 5), as well as the monitoring system put in place for the operational management of the risk (Section 6).