Scree is a collection of broken rock fragments at the base of a cliff or other steep rocky mass that has accumulated through periodic rockfall. Landforms associated with these materials are often called talus deposits. Talus deposits typically have a concave upwards form, where the maximum inclination corresponds to the angle of repose of the mean debris particle size. The exact definition of scree in the primary literature is somewhat relaxed, and it often overlaps with both talus and colluvium.
The term scree comes from the Old Norse term for landslide, skriða, while the term talus is a French word meaning a slope or embankment.
In high-altitude arctic and subarctic regions, scree slopes and talus deposits are typically adjacent to hills and river valleys. These steep slopes usually originate from late-Pleistocene periglacial processes. Notable scree sites in Eastern North America include the Ice Caves at White Rocks National Recreation Area in southern Vermont and Ice Mountain in eastern West Virginia in the Appalachian Mountains. Screes are most abundant in the Pyrenees, Alps, Variscan, Apennine, Orocantabrian, and Carpathian Mountains, Iberian peninsula, and Northern Europe.
The term scree is applied both to an unstable steep mountain slope composed of rock fragments and other debris, and to the mixture of rock fragments and debris itself. It is loosely synonymous with talus, material that accumulates at the base of a projecting mass of rock, or talus slope, a landform composed of talus. The term scree is sometimes used more broadly for any sheet of loose rock fragments mantling a slope, while talus is used more narrowly for material that accumulates at the base of a cliff or other rocky slope from which it has obviously eroded.
Scree is formed by rockfall, which distinguishes it from colluvium. Colluvium is rock fragments or soil that is deposited by rainwash, sheetwash, or slow downhill creep, usually at the base of gentle slopes or hillsides. However, the terms scree, talus, and sometimes colluvium tend to be used interchangeably.