Scree
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.
Colluvium is rock fragments or soil deposited by rainwash, sheetwash, or slow downhill creep, usually at the base of gentle slopes or hillsides.
[11][12] Talus deposits typically have a concave upwards form, where the maximum inclination corresponds to the angle of repose of the mean debris particle size.
[15] The formation of scree and talus deposits is the result of physical and chemical weathering acting on a rock face, and erosive processes transporting the material downslope.
[citation needed] In high-altitude arctic and subarctic regions, scree slopes and talus deposits are typically adjacent to hills and river valleys.
Since water expands by 9% when it freezes, it can generate large forces that either create new cracks or wedge blocks into an unstable position.
[20] Many argue that frost heaving, like that known to act in soil in permafrost areas, may play an important role in cliff degradation in cold places.
Particularly during the initial colonization process, the lichen often inserts its hyphae into small fractures or mineral cleavage planes that exist in the host rock.
[citation needed] Freeze-thaw action of the entire lichen body due to microclimatic changes in moisture content can alternately cause thermal contraction and expansion,[23] which also stresses the host rock.
For example, Lech dl Dragon, in the Sella group of the Dolomites, is derived from the melting waters of a glacier and is hidden under a thick layer of scree.
[citation needed] The amount of energy reaching the surface of the ice below the debris can be estimated via the one-dimensional, homogeneous material assumption of Fourier's law:[25]
[26] Instead, the debris blanket will act to insulate the glacier, preventing incoming radiation from penetrating the scree and reaching the ice surface.
[26] In addition to rocky debris, thick snow cover can form an insulating blanket between the cold winter atmosphere and subnivean spaces in screes.
[citation needed] Patchy permafrost, which forms under conditions <0 °C, probably exists at the bottom of some scree slopes despite mean annual air temperatures of 6.8–7.5 °C.
[29] Scree microclimates maintained by circulating freezing air create microhabitats that support taiga plants and animals that could not otherwise survive regional conditions.
[28] A Czech Republic Academy of Sciences research team led by physical chemist Vlastimil Růžička, analyzing 66 scree slopes, published a paper in Journal of Natural History in 2012, reporting that: "This microhabitat, as well as interstitial spaces between scree blocks elsewhere on this slope, supports an important assemblage of boreal and arctic bryophytes, pteridophytes, and arthropods that are disjunct from their normal ranges far to the north.
This freezing scree slope represents a classic example of a palaeo refugium that significantly contributes to [the] protection and maintenance of regional landscape biodiversity.
"[28] Ice Mountain, a massive scree in West Virginia, supports distinctly different distributions of plant and animal species than northern latitudes.
