Résumé
Numerous small, low volume rockfalls around the crest of the Italian and French Alps, principally formed from calcareous mica schist and metabasalt, have impeded travel across the major cols for millennia. As documented by Polybius and Livy in the ancient literature, Hannibal's Army was blocked by a two-tier rockfall on the lee side of the Alps, a rubble sheet of considerable volume that delayed his exit into the upper Po River Country. An in-depth study of the possible cols reveals that the only such two-tier landform lies below the Col de la Traversette, at ∼2600 m above sea level. In addition, it represents a problem in applied geomorphology, namely, to accurately determine the nature of the surface rubble sheet in Hannibal's time (218 bc). A reconstruction of the initial deposit, likely Late Glacial, following the retreat of the Po Glacier, is based upon an analysis of the source rock and geological setting. Further specifications on the geometry of the Neoglacial cover sediment are based on weathering characteristics, lichen cover and soil development. The ‘myth' that Hannibal fired the rockfall to comminute boulders is plausible given the vegetation records which support tree growth nearby, but is unsubstantiated by the lack of any carbonized rock.