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Silica-sesquioxide ratio <br />The ratio of the number of molecules of silica to the number of molecules of <br />alumina and iron oxide. The more highly weathered soils or their clay fractions <br />in warm-temperate, humid regions, and especially those in the tropics, generally <br />have a low ratio. <br />Silt <br />As a soil separate, individual mineral particles that range in diameter from the <br />upper limit of clay (0.002 millimeter) to the lower limit of very fine sand (0.05 <br />millimeter). As a soil textural class, soil that is 80 percent or more silt and less <br />than 12 percent clay. <br />Siltstone <br />An indurated silt having the texture and composition of shale but lacking its fine <br />lamination or fissility; a massive mudstone in which silt predominates over clay. <br />Similar soils <br />Soils that share limits of diagnostic criteria, behave and perform in a similar <br />manner, and have similar conservation needs or management requirements for <br />the major land uses in the survey area. <br />Sinkhole (map symbol) <br />A closed, circular or elliptical depression, commonly funnel shaped, <br />characterized by subsurface drainage and formed either by dissolution of the <br />surface of underlying bedrock (e.g., limestone, gypsum, or salt) or by collapse <br />of underlying caves within bedrock. Complexes of sinkholes in carbonate-rock <br />terrain are the main components of karst topography. <br />Site index <br />A designation of the quality of a forest site based on the height of the dominant <br />stand at an arbitrarily chosen age. For example, if the average height attained <br />by dominant and codominant trees in a fully stocked stand at the age of 50 <br />years is 75 feet, the site index is 75. <br />Slickensides (pedogenic) <br />Grooved, striated, and/or glossy (shiny) slip faces on structural peds, such as <br />wedges; produced by shrink-swell processes, most commonly in soils that have <br />a high content of expansive clays. <br />Slide or slip (map symbol) <br />A prominent landform scar or ridge caused by fairly recent mass movement or <br />descent of earthy material resulting from failure of earth or rock under shear <br />stress along one or several surfaces. <br />Slope <br />The inclination of the land surface from the horizontal. Percentage of slope is <br />the vertical distance divided by horizontal distance, then multiplied by 100. <br />Thus, a slope of 20 percent is a drop of 20 feet in 100 feet of horizontal <br />distance. <br />Custom Soil Resource Report <br />59 Index #10