Rock avalanches are characterized by granular flows of dry and disintegrating rock masses detached from a mountain slope. They deposit large volumes of megablocks, which have distinct surface features and are known to cause catastrophic damage. The mechanisms and dynamic processes of such disasters are still under debate, owing to insufficient real-time data. Here, field surveys and high-resolution digital elevation models (DEMs) were used to investigate the dynamic processes of the Tagharma rock avalanche (Kongur Mountain, Eastern Pamir, China), providing a unique case study for determining the long runout mechanisms and dynamic processes of the avalanche based on its morphology and sedimentology. The processes and dynamics of the event were reconstructed through fragmented rock debris combined with surface morphology and substrate implications. We analyzed how fragmentation occurs at impact and studied the generated fragment size distributions. Finally, the emplacement dynamics of the Tagharma rock avalanche were reconstructed. Our results indicate that the dynamic process of the Tagharma rock avalanche consisted of two main stages: (i) foliated megablocks having a strong interaction between the rock avalanche mass and the ground (dynamic rock mass disintegration), and (ii) distal "passive spreading" when the avalanche mass encountered deformable substrates (sediment bulldozing).