Scree, also called talus and detritic cone, is a term given to broken rock that appears at the bottom of
crags, mountain cliffs or valley shoulders, forming a scree slope. The maximum inclination of such deposits corresponds to the angle of reposeof the mean debrissize.
The term "scree" comes from the
Old Norseterm for landslide, "skriða". [cite web|title=Scree|work=Online Etymology Dictionary|url=http://www.etymonline.com/index.php?term=scree|accessdate=2006-04-20]
The term "scree" is sometimes used interchangeably with "talus", though scree refers to small rocks, like mixed size gravel and loose as dirt (e.g., anything smaller than a human fist), while talus can refer to rocks larger than scree. [cite web|title=Scree|work=Backpacker Magazine article on mountain skills.|url=http://www.backpacker.com/june_2001_skills_mountain_hiking_skills/article/2154?page=2|accessdate=2008-04-22] Going downhill on sturdy boots one is often able to slip-slide down a scree slope. Uphill takes more effort because one tends to slide a bit with every step. Talus is easier for stepping up, but not suitable for sliding down.
The formation of scree is often a result of
frost heaving, one of the physical weatheringprocesses that slowly wear mountains down. During the day, water can flow into cracks and crevices in the rock. If the temperature drops sufficiently, for example with the onset of evening, the water freezes. Since water expands when it freezes, it forms a powerful wedge which can eventually break out pieces of rock. A repeated cycle of freeze-thaw can lead to significant erosion and most of the loose rock or scree slopes so common in the mountains have been formed in this way.
For mountaineers screes may pose a danger. In a similar way,
gravitycauses an almost constant scree inclination by the impulse of falling rocks.
Formation of scree can occur on
planets or moons other than the Earth. For example it is fairly common for fresh craters on the Moonto have piles of talus along the base of the inner wall.
Scree can also be the result of human activity, such as the scree beneath the sculpture
Mount Rushmorein South Dakota.
Angle of repose
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