SOIL SURVEY

-172-Clay films (skins) - Oriented clay particles forming a coating on the surface of thesoil aggregates, mineral grains and in pores . Clay bridges are similar to cla yfilms, but instead of forming coatings, they form a latticework or bridgesamong the sand grains . The latter are found in medium and coarse texture dsoils .Clod - A compact, coherent mass of soil produced artifically, usually by the activitiesof man by plowing, digging etc . , especially when those operations ar eperformed on soils that are either too wet or too dry .Coarse fragments - Rock or mineral particles greater than 2 mm in diameter .Cobbles - Rock fragments 7 .5 to 25 cm in diameter .Cobbly -Containing large quantities of cobblestones .Colluvium - A deposit of heterogeneous material that as a result of mainly gravitationalaction has moved or is moving down a slope, and has accumulated amantle of about 50 cm or more in thickness .Color, soil - Soil colors are estimated by comparison with a Munsell color chart .The Munsell system specifies the relative degrees of the three simple variable sof color; hue, value and chroma . For example 10YR 6/4 means a hue of 10YR ,a value of 6, and a chroma of 4 .Concretion - A mass or concentration of a chemical compound, such as calciumcarbonate or iron oxide, in the form of a grain or nodule of varying size ,shape, hardness and color found in soil and in rock .Consistence, soil - (i) The resistance of a material to deformation or rupture .(ii) The degree of cohesion or adhesion of the soil mass . Terms used fo rdescribing consistency at various soil moisture contents are (CSSC 1974) :wet soil - non-sticky, slightly sticky, sticky, very sticky, nonplastic,slightly plastic, plastic and very plastic ;moist soil - loose, very friable, friable, firm, very firm an dextremely firm ;dry soil - loose, soft, slightly hard, hard, very hard and extremel yhard .Control section - The vertical section upon which the taxonomic classification o fsoil is based . The control section usually extends to a depth of 100 cm (40 in )in mineral and to 160 cm (64 in) in organic materials .Creep - Slow mass movement of soil and soil material down relatively steep slope sprimarily under the influence of gravity, but facilitated by saturation wit hwater and by alternate freezing and thawing .