LIDAR reveals an active landslide along US 460 west of Narrows (Giles County)
Source: US Geological Survey (USGS), The National Map
Geologists identify five types of landslides, where rocks, debris or earth move down a slope: falls, topples, slides, spreads, and flows. Gravity is always a factor is moving material down a slope. Landslides are where a distinct mass moves at a faster rate than the adjacent material. The movement can be quick like a rockfall, or occur as a slow shift of a slice of a hillside.
Earthquakes and hurricanes can trigger landslides. Climate change can result in freezing and thawing cycles that cause a mass to move downslope gradually. Shifts in groundwater flow can initiate and halt landslides. Erosion by a stream undercutting a mass of rock, or by construction of a highway/railroad, can initiate "mass wasting" and force expensive repairs to clear clots of dirt/rock that clog a transportation artery.1
landskide risk in higher in the Blue Ridge and Allegheny Plateau than in the Piedmont
Source: US Geological Survey (USGS), Map Showing Inventory and Regional Susceptibility for Holocene Debris Flows, and Related Fast-Moving Landslides in the Conterminous United States (1999)