Editing Duricrust (section)

{{Short description|Type of surface soil layer}}
{{Infobox soil
| name                  = Duricrust
| alternative_name      = 
| image                 = De Yalgo a Dori Marco Schmidt 0922.jpg
| image_caption         = A duricrust [[inselberg]] near [[Dori, Burkina Faso|Dori]], [[Burkina Faso]]
| image_size            = 
| type                  = 
| classification_system = 
| code                  = 
| profile               = 
| mineral               = Soluble minerals
| process               = 
| parent_material       = 
| climate               = Arid
| ph                    = 
| horizons              = 
| composition           = Various
| composition_secondary = Various
}}

'''Duricrust''' is a hard layer on or near the surface of [[soil]]. Duricrusts can range in thickness from a few millimeters or centimeters to several meters.

It is a general term (not to be confused with [[duripan]]) for a zone of chemical [[precipitation (chemistry)|precipitation]] and hardening formed at or near the surface of [[sedimentary rock|sedimentary]] bodies through [[pedogenic]] or non-pedogenic processes. It is typically formed by the accumulation of [[soluble]] [[minerals]] deposited by mineral-bearing waters that move upward, downward, or laterally by [[capillary action]]. It is commonly assisted in arid settings by [[evaporation]].<ref name="DixonOthers2009a">Dixon, J.C. and McLaren, S.J., 2009. ''Duricrusts''. In A.J. Parsons and A.D. Abrahams, ed., pp. 123-151. ''Geomorphology of desert environments.'' Springer, Dordrecht. {{ISBN|978-1-4020-5718-2}}</ref><ref name="Woolnough1930a">Woolnough, W.G., 1930. ''The influence of climate and topography in the formation and distribution of products of weathering.'' ''Geological Magazine'', 67(3), pp.123-132.</ref> There are different types of duricrusts, each distinguished by a dominant mineralogy. For example, [[ferricrete]] ([[laterite]]) is dominated by [[sesquioxide]]s of [[iron]]; alcrete ([[bauxite]]) is dominated by sesquioxides of [[aluminum]]; [[silcrete]] by [[silica]]; [[calcrete]] ([[caliche]]) by [[calcium carbonate]], and gypcrete ([[gypcrust]]) by [[gypsum]].<ref name="DixonOthers2009a"/>

Duricrust is often studied during missions to Mars because it may help prove that the planet once had more water. Duricrust was found on [[Mars]] at the [[Viking 2]] landing site, and a similar structure, nicknamed "Snow Queen", was found under the [[Phoenix (spacecraft)|Phoenix]] landing site.<ref>{{cite web
 |title=Holy Cow, Snow Queen! Phoenix Landed on Ice, Team Thinks
 |last=Rayl
 |first=A.J.S.
 |work=The Planetary Society
 |date=June 1, 2008
 |url=http://www.planetary.org/news/2008/0601_Holy_Cow_Snow_Queen_Phoenix_Landed_on.html
 |accessdate=November 12, 2008
 |url-status=dead
 |archiveurl=https://web.archive.org/web/20080605010056/http://www.planetary.org/news/2008/0601_Holy_Cow_Snow_Queen_Phoenix_Landed_on.html
 |archivedate=June 5, 2008
}}</ref> Phoenix's duricrust was later confirmed to be water-based.<ref>{{Cite APOD
 | title = Phoenix and the Holy Cow
 | date = November 12, 2008
 | access-date = November 12, 2008
}}</ref>