Scree
712625
223139930
2008-07-02T19:16:05Z
Davemcarlson
855320
added reference to man-made scree caused by sculptures
[[Image:Yamnuska bottom cliff.jpg|250px|thumb|right|A scree slope at the bottom of [[Mount Yamnuska]], [[Alberta]].]]
[[Image:Crossf3.jpg|250px|thumb|right|Climber ascending talus slope on the west flank of [[Cross Fell]], [[England]].]]
'''Scree''', also called '''talus''' and '''detritic cone''', is a term given to broken [[Rock (geology)|rock]] that appears at the bottom of [[crag]]s, mountain [[cliff]]s or [[valley shoulder]]s, forming a scree slope. The maximum inclination of such deposits corresponds to the [[angle of repose]] of the mean [[debris]] size.
The term ''scree'' comes from the [[Old norse]] term for landslide: skriða<ref>{{cite web|title=Scree|work=Online Etymology Dictionary|url=http://www.etymonline.com/index.php?term=scree|accessdate=2006-04-20}}</ref>. <!-- The word imitates the sound that scree makes when the pile moves. -- Could we have a reference for this? Thanks -->
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.<ref>{{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}}</ref> 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 [[weathering]] processes 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 [[freezing|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 [[mountaineering|mountaineer]]s screes may pose a danger. In a similar way, [[gravity]] causes an almost constant scree inclination by the impulse of falling rocks.
Formation of scree can occur on [[planet]]s or moons other than the [[Earth]]. For example it is fairly common for fresh [[impact crater|craters]] on the [[Moon]] to 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 Rushmore]] in [[South Dakota]].
==See also==
* [[Angle of repose]]
* [[Cirque (landform)]]
* [[Gravel]]
* [[Mass wasting]]
* [[Landslide]]
==References==
<references />
[[Category:Landforms]]
[[Category:Mountaineering]]
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[[de:Talus (Geologie)]]
[[it:Ghiaione]]
[[sl:Melišče]]