. Soil physics and management. omes completely filled. Accumulations of peat alsooccur around springs, giving rise to quaking bogs (Fig. 20). Inpoorly drained areas the moss may grow on the surface of the soilin sufficient amounts to form peat. Oftener, however, it forms onlya soil rich in organic matter. 30 SOIL PHYSICS AND MANAGEMENT A wet woods swamp is where a forest area with a slope of lessthan five degrees has been transformed into a swamp through theaccumulation of vegetable material and the consequent increase ofmoisture. The original forest may be entirely destroyed and re-placed by
. Soil physics and management. omes completely filled. Accumulations of peat alsooccur around springs, giving rise to quaking bogs (Fig. 20). Inpoorly drained areas the moss may grow on the surface of the soilin sufficient amounts to form peat. Oftener, however, it forms onlya soil rich in organic matter. 30 SOIL PHYSICS AND MANAGEMENT A wet woods swamp is where a forest area with a slope of lessthan five degrees has been transformed into a swamp through theaccumulation of vegetable material and the consequent increase ofmoisture. The original forest may be entirely destroyed and re-placed by plants adapted to swamp conditions. An ablation sicamp is produced by the solution and carrjdngaway of certain more soluble strata, such as gypsum, salt or evenlimestone, between less soluble strata, thus causing a lowering ofthe surface and bringing about swamp conditions. II. TRAXSPOETED FORIMATIOXS Various agencies are engaged in the movement of soil material,namely: gravity, water, ice, and wind, and the deposits formed by. Fig. 20.—Hummocks 6 to 12 inches high, found in swampy places produced by trampling ofstock. Commonly called bogs. (R. W. Dickenson.; these are known as colluvial, sedimental, glacial, and eolial. Duringthe transportation of these materials many particles are reducedin size and other changes brought about. Over ninety per cent ofthe soils surveyed by the Bureau of Soils ^ in the United States areformed from transported material. 1. Colluvial or Gravity-laid Soils.—Gravity might be said tobe the active agent in the formation of all of the above, but gravity,unaided, is very limited in its work, being confined to areas ofvertical cliffs or very steep slopes. The material transported bygravity and deposited at the base of cliffs consists of a heterogeneousmixture of detritus that has been loosened by the processes ofweathering and carried downward by gravity. This accumulationis commonly designated as talus or cliff debris (Figs. 21 and 22). RESIDUAL, G
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