CLASSIFICATION BY THE BUREAU OF SOILS 105 



and coarse rounded gravel. They are derived mainly from vol- 

 canic rock. 



(b) River Flood Plains. Billings Series. The soils are gray 

 to drab, with the subsoils similar in color, structure and texture. 

 They are derived mainly from shales and sandstones, and are adapted 

 to a wide range of crops under favorable conditions of irrigation. 



Laramie Series. These soils are light brown to grayish brown 

 with a slight reddish cast. The subsoils are lighter gray or more 

 reddish, sometimes becoming yellowish gray, and are underlain by 

 sand or sandy loam with gravel. They are treeless plains. 



Mesa Series. The soils are pinkish red or reddish gray to 

 light reddish brown. The subsoils are of lighter reddish gray or 

 gray color and heavier texture. Where irrigated, fruits, alfalfa, 

 and general farm crops do well. 



X. NORTHWESTERN INTERMOUNTAIN REGION 



This region lies between the Pacific Coast region on the west, 

 the Kocky Mountain region on the north and east, and the Great 

 Basin region on the south. 



The rocks of this region are mostly effusive or volcanic and the 

 soil material is derived largely from these, either by weathering of 

 solid material or from fragments ejected from volcanoes. 



(a) Uplands. Ephrata Series. These soils are of light gray- 

 ish brown to yellowish brown color, while the subsoils are porous but 

 compact. They consist largely of glacial subangular or rounded 

 gravel or boulders. 



Quincy Series. The soils are grayish brown and usually of 

 loose porous structure. The subsoils are similar in color and tex- 

 ture but slightly more compact. They are wind-laid material. 



Walla Walla Series. This series consists of sticky, brown to 

 dark brown soils about three feet deep underlain by yellow silt loam 

 subsoils which are often sticky and plastic. The topography is high 

 rolling hills. The soil material is wind-laid. Wheat, barley, and 

 oats are the principal crops. 



Winchester Series. The soils and subsoils of this series are 

 dark gray to nearly black and consist mainly of dark-colored angular 

 fragments of basalt. The fine material is wind-laid. 



(b) River Flood Plains. Boise Series. Soils are of light 

 gray to light brown color. The subsoils are similar to the soils in 

 color. They are underlain by a calcareous hardpan stratum. They 

 are of alluvial origin. 



