Duricrust

{{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

| image_size =

| type =

| classification_system =

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| mineral = Soluble minerals

| process =

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| climate = Arid

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| 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 and hardening formed at or near the surface of 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.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}}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. There are different types of duricrusts, each distinguished by a dominant mineralogy. For example, ferricrete (laterite) is dominated by sesquioxides of iron; alcrete (bauxite) is dominated by sesquioxides of aluminum; silcrete by silica; calcrete (caliche) by calcium carbonate, and gypcrete (gypcrust) by gypsum.

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 landing site.{{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

}} Phoenix's duricrust was later confirmed to be water-based.{{Cite APOD

| title = Phoenix and the Holy Cow

| date = November 12, 2008

| access-date = November 12, 2008

}}