A rockslide is a type of landslide caused by rock failure in which part of the plane of failure passes through intact rock and material collapses en masse and not in individual blocks. While a landslide occurs when loose dirt or sediment falls down a slope, a rockslide occurs only when solid rocks are transported down slope. The rocks tumble downhill, loosening other rocks on their way and smashing everything in their path.Slides are rapid downslope movements of blocks along a bedding plane, joint, or area of weakness. The blocks tend to break up into smaller pieces as the slide moves downslope and large pieces collide with each other. These pieces can travel a great distance due to the force of the falling rock. For these slides, failure occurs along a well-defined shear plane; blocks of material within the failure may move as coherent units, preserving relict structures. Rockslides can be some of the most dangerous forms of deformation because of the way that large rocks are traveling quickly down slope; this large material can cause massive damage to anything in its path.The mode of failure is different from that of a rockfall in that the material is sliding or slumping down a slope instead of toppling off a cliff.Fast-flowing rock slides or debris slides behave similarly to snow avalanches, and are often referred to as rock avalanches or debris avalanches.