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Physical Geography : What are some of the common soil colors and what do they mean?

March 24, 2016 | Author: | Posted in nature

Soil Color is the first impression one has when viewing soil and we identify some places with their soil color . The Red River (Mississippi watershed ) carries sediment eroded from extensive reddish soils like Port Silt Loam in Oklahoma . The Yellow River in China carries yellow sediment from eroding loessal soils . Mollisols in the Great Plains are darkened and enriched by organic matter (Soil Survey Division Staff 1993 . Thus soil color gives some meaningful information about the life cycle , moisture content , physical state and chemical composition of the soil

Common soil colors [banner_entry_middle]

range from shades and tints of yellow , pale to bright reddish or orange , grey to black shades or brown hues

Often described by using general terms , such as dark brown , yellowish brown , etc , soil colors are described more technically by using Munsell soil color charts , which separate color into components of hue (chromatic composition of light or relation to red , yellow and blue value (lightness or darkness ) and chroma (paleness or strength

Technically elements of complete soil color s are the color name , the color notation , the water state : moist or dry and the physical state : broken , rubbed , crushed or smoothed (Soil Survey Division Staff 1993 . The complete color notation is visualized as follows “brown (10YR 5 /3 , dry , crushed

Soil color is primarily influenced by soil mineralogy and is a clue to the minerals present in it . Iron minerals , by far , provide the greatest variety of pigments in earth and soil . Relatively large crystals of goethite give the ubiquitous yellow pigment of aerobic soils . Smaller goethite crystals produce shades of brown . Hematite adds rich red tints Large hematite crystals give a purplish-red color to geologic sediments (Appendix – I

Color development and distribution of color within a soil pro are part of weathering . As rocks containing iron or manganese weather , the primary minerals in soil-parent material oxidize and combine into new and colorful compounds . Iron forms small crystals with a yellow or red color , organic matter decomposes into black humus , and manganese forms black mineral deposits . These pigments give soil its various colors and patterns (Lynn Pearson , 2000 Color – or lack of color – can also tell us something about the environment as soil colors and patterns are further affected by environmental factors . Aerobic conditions produce uniform or gradual color changes while anaerobic /reducing environments (lacking oxygen ) or wet conditions result in disrupted color flow with complex , mottled patterns and points of color concentration . Soil color often indicates soil moisture status and is used for determining hydric soils (Lynn Pearson , 2000 . Along seacoasts , tide waters saturate soils twice daily bringing soluble sulfate anions . Anaerobic bacteria use the sulfate as an electron acceptor and release sulfide (S2- ) which combines with ferrous iron to precipitate black iron sulfide . Galuconitic green sands form in shallow ocean water near a coast . A little carbonate dissolves in water , moves downward , and precipitates in soft white bodies

Organic Matter also has an influence on Soil Color . Soil has living organisms and dead organic matter , which decomposes… [banner_entry_footer]

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