28 



SOIL PHYSICS AND MANAGEMENT 



moss gives rise to immense. deposits of peat, in some cases probably 

 hundreds of feet in thickness. Grasses usually grow with the 

 mosses and add to the accumulation. In more southern regions, 

 grasses, cattails and sedges form' a large part of the deposit, while 

 in subtropical regions the palmetto and saw grass constitute the 

 chief plants from which the organic matter is derived. 



Swamps may be divided into river swamps, peat bogs, lake 

 swamps, quaking bogs, climbing bogs, wet woods and ablation 

 swamps. These terms are almost self-explanatory. River swamps 

 may occur in the flood plain where ox-bow lakes, representing 



Fio. 16. Ox-bow lakes formed by shifting of channel, A, B and C. Sedimentation on 

 inner side of curve. (Shaler,) 



former channels, have been transformed into swamps by filling with 

 both organic matter arid sediment (Fig. 16). In wide flood plains 

 low swampy land may lie back toward the bluffs away from the 

 river. Delta lands are usually swampy. 



Peat deposits may be formed (1) in low places where the water 

 is shallow but the supply constant (Figs. 17 and 18). This type 

 is found in sand dune or gravelly areas where the water seeps out 

 at the base of sand hills or gravel terraces. Peat formed in this 

 way is rarely of any great depth. Peat bogs may also be formed 

 (2) as shown in figure 19. The sphagnum moss begins to grow at 

 the margins of the lake and extends out over the water, forming a 

 quaking bog, and up the bank, as a climbing bog. The growth over 

 the water is quite rapid and the small pond or lake may become 



