Duricrust

(geology) The case-hardened soil crust formed in semiarid climates by precipitation of salts; contains aluminous, ferruginous, siliceous, and calcareous material.

A hard capping found at the surface of the soil in tropical uplands, such as the Djebel Qarah of Saudi Arabia.

Duricrusts are thought by some to be a plinthite horizon, originally formed in the B horizon, but now revealed by erosion since plinthite hardens on exposure to the air. The duricrust would therefore be the remains of a fossil soil. An alternative explanation is that duricrusts are formed through ‘core weathering’ processes, during which rock degradation progresses from the subsurface to the surface of bare rock. Other processes in the formation of duricrust include evaporation of a lake, of groundwater, or of subsurface and surface waters moving across alluvial fans and pediments.

Duricrust refers to a thin hard layer on or near the surface of soil, usually a few millimeters to a few centimeters thick.

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 and (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, commonly assisted in arid settings by evaporation. (Dixon, 1994; Woolnough, 1930; NADMSC SLTT, 2004)

Duricrust was found at the Viking 2 landing site, and a similar structure, nicknamed "Snow Queen," was found under the Phoenix landing site.^[1] Phoenix's duricrust was later confirmed to be water-based.^[2]

Duricrust is one of the things often studied during Mars missions because it may help prove the planet once had more water. Minerals often found in duricrust include silica, iron, calcium, and gypsum.

References

1. ^ "Holy Cow Snow Queen Phoenix". http://www.planetary.org/news/2008/0601_Holy_Cow_Snow_Queen_Phoenix_Landed_on.html. Retrieved on 2008-12-11. 
2. ^ "Phoenix and the Holy Cow". http://apod.nasa.gov/apod/ap081112.html. Retrieved on 2008-12-11. 

External links

• Description
• NASA: The Sands of Mars

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