rockslide

Rockslide is a type of mass wasting in which a coherent block of rock moves downslope along a well-defined rupture surface. The sliding mass typically remains in contact with the slide plane, and may travel as a translation along bedding planes, fractures, or faults. Rockslides are distinct from rockfalls, in which individual rocks or small fragments detach and descend independently, and from slow, creeping slides.

Causes and triggers include gravity acting on steep, fractured slopes; weathering and undercutting; pore-pressure changes from rainfall or snowmelt; freeze–thaw cycling that opens existing fractures; and seismic shaking. Rockslides can be triggered by earthquakes or human activities that destabilize slopes, such as mining or quarrying.

Movement may range from slow to rapid. When the failure surface is planar and the mass remains relatively coherent, it is called a translational rockslide. If the rock mass breaks into many pieces and travels as a turbulent debris wave, it is sometimes described as a rock avalanche or rapid rockslide. Rockslides often leave a scarp at the head and a depositional toe downslope.

Hazards include road and railway closures, dam formation in valleys, flooding if a dam is breached, and damage to infrastructure and communities. Notable examples include the Frank Slide of 1903 in Alberta, Canada, which buried part of the town of Frank, and various large rockslides in the Alps and Himalayas.

Mitigation and monitoring rely on geological mapping, stability analysis, drainage improvement, removal of unstable blocks, rockfall nets or retaining structures, and controlled blasting. Early warning systems using tiltmeters, crack meters, and seismic sensors can provide warning before rapid movement.