HOOD RIVER-WHITE SALMON RIVER AREA. 33 



types from which a small admixtm:"e of such material may have been 

 derived. 



The Hood silt loam is found m both of the valleys in this area. In 

 the Hood River Valley it covers the greater part of the lower valley 

 floor between the Hood River and the range of mountains along the 

 eastern boundary of the area. A relatively small area is also found 

 just west of the Hood River, where it occurs in a long, narrow body 

 approximately parallel mth the stream. In the White Salmon 

 Valley the type occupies aU of the slightly elevated lands along the 

 White Salmon River, from a point about 3 miles north of Husum 

 southward to the Columbia River. It also forms a long, narrow 

 body in the dramage basm of Jewett Creek, a short distance north of 

 the town of White Salmon. 



In the Hood River VaUey the general slope of this type is from the 

 mountains toward the river. It has a generally uniform surface, 

 but includes a number of low, broad ridges. Along Hood River the 

 type forms in places a nearly precipitous bluff, or slopes more gently 

 to the stream. In the latter case the areas are not too steep for culti- 

 vation. In the White Salmon Valley the topography is subject to 

 considerable variation, the type occurrmg either as relatively smooth 

 slopes above the streams or as prominent knolls and ridges rising 

 toward the mountams on each side. 



The drainage is generally good, though where the soil is unusually 

 compact the internal movement of water is retarded. In an area in 

 the vicinity of OdeU the surface drainage is but partially developed. 

 Here the artificial drainage may be provided b}^ digging ditches and 

 laymg tiles, but where the compact subsoil is found blasting will have 

 to be employed to improve the conditions. 



The origin and mode of formation of this type is not altogether 

 clear, but it seems to have been derived from old sedimentary deposits 

 laid down over areas of basalt or glacial till. In the White Salmon 

 Valley the substratum of tiU is apparently absent, but the simi- 

 larity of color, texture, and structure m tiie bodies of tliis soil on both 

 sides of the Columbia River indicate a similarity in the method of 

 formation of the soil proper. 



The uniform fuieness of the material suggests that it was deposited 

 in quiet waters. The deposition probably took place iti sheltered 

 bays or estuaries occupying the vaUeys durmg a period of depression. 

 One or more periods of relative depression are believed to have taken 

 place subsequent to the active period of glaciation. At such times 

 the waters of the Columbia and its tributaries must have backed far 

 up the valleys. 



The deposits probably consist mainly of glacial sediments derived 

 from basaltic and andesitic rocks and carried into the area of deposi- 



