<p>Deposit morphologies and sedimentary characteristics are direct threads for investigating rock avalanches. However, these two characteristics and mobility become ambiguous because of the initial discontinuity sets. Therefore, experiments were conducted with different initial configurations of blocks (the long axis of the blocks perpendicularly placed to the strike of the inclined plate EP, parallel to the strike of the inclined plate LV, perpendicular to the inclined plate LP, randomly R and without the blocks NB as a control experiment) and different slope angles in this study. The experimental materials comprised both block and granular materials to simulate large blocks and matrixes, respectively, in natural rock avalanches. The results revealed that the mobility of the mass flows was enhanced at LV, LP and R configurations, whereas it was restricted at the EP configuration. The mobility decreased with the increase in slope angles at LV configurations. Strand protrusion of the blocks made the elevation of the deposits at LV configuration larger than that at EP, LP, and R configurations. An alternate deflection of the blocks for the bending moment that was created during the lateral spread of the mass flows was responsible for creating zigzag structures. Varying degrees of deflection of the blocks demonstrated different levels of collision and friction in the interior of the mass flows; the most intensive collision was observed at EP. In the mass deposits, the blocks’ orientation was affected by their initial configurations and the motion process of the mass flows. This research would provide more ideas for investigating rock avalanches’ surface morphologies and sedimentary characteristics.</p>