GEOLOGICAL CLASSIFICATION OF SOILS 43 



31. Marine soHs. — The sediments which are con- 

 tinually being carried away by rivers are eventually 

 deposited in the sea, the coarser fragments near the 

 shore, the finer particles at considerable distances. This 

 layer of material, varying in thiclaiess, consists of stratified 

 gravels, sands, and clays, and is of a rather recent age 

 compared with the residual soils. It has not become 

 consolidated as yet, because of insufficient pressure and 

 time. When such material becomes raised above the 

 sea, due to a change in land elevation, it is classified as a 

 marine soil. It has been worn and triturated by a num- 

 ber of agencies. First, the forces necessary to throw it 

 into stream suspension were active, and next it was 

 swept into the ocean to be deposited and stratified, 

 possibly after being pounded and eroded by the waves 

 for years. At last came the emergence above the sea 

 and the action of the forces of weathering in situ. The 

 latter effects are not of great moment, since with our 

 most important marine soils they have been at ^vork 

 for but a comparatively short time, speaking geologically. 



32. Characteristics of marine soils. — Marine soils, 

 while much younger than residual soils, are usually more 

 worn and ordinarily show a less amount of the important 

 food elements. This is because of their almost con- 

 tinuous contact with water from the time when they are 

 swept into the streams until they rise above the sea level 

 as a soil. They are generally characterized as sandy 

 soils, because the forces to which they have been sub- 

 jected have worn out and dissolved most of the minerals 

 except quartz. This gives them a coarse texture and 

 fits them particularly for trucking soils. Sands, sandy 

 loams, and loams predominate usually in such soil prov- 

 inces, although clays and silts may occasionally be 



