262 University of California Publications in Geology [Vol. 10 



miles. The bluffs end at a point across the river and a short distance 

 below the town of White Bluffs. Where the beds are not locally re- 

 duced by erosion, the crest line of the bluffs is remarkably even (pi. 

 13, fig. 2). Without having determined its elevation above the river 

 at many points, the crest appears to maintain its height of about 

 five hundred feet above the stream throughout the whole thirty miles. 



Between the northwestern end of the White Bluffs and Priest 

 Rapids, a distance of fifteen to eighteen miles upstream, no high 

 bluffs occur, but low light-colored exposures appear some distance 

 from the river. The dissected character of this area indicates that it 

 has suffered marked degradation in contrast to the relatively undis- 

 sected areas lying to the east of the Columbia in the Ringold region. 

 The more marked dissection has probably resulted from the greater 

 drainage derived from the Saddle Mountains to the north. 



The White Bluffs, extending along the east side of the Columbia 

 River, have no counterpart in similar features on the opposite side 

 of the stream. To the west of Hanford is an area with a rolling 

 topography, on which occur occasional outcrops of soft beds similar 

 to those in the White Bluffs. This area extends westward to the base 

 of the Yakima Range and has a maximum width of perhaps sixteen 

 miles. Practically all of it lies at less elevation above the Columbia 

 than the top of the White Bluffs. It is believed that the Ringold once 

 extended over this region of low hills between Hanford and the base 

 of the Yakima Range, and that it was largely cut away by the Colum- 

 bia before it had shifted eastward to its present position, and while 

 its channel lay at a higher level. It has been this gradual shifting 

 eastward, continued to the present time, which has produced the 

 White Bluffs on the east side of the Columbia, in contrast to the de- 

 graded character of the area on the west side. The cause of the 

 shifting cannot be stated with certainty, but it is probably due in 

 part to deflection of the stream by the north side of the Yakima 

 Range. 



The surface extending several miles to the eastward from the 

 summit of the White Bluffs is remarkably even, excepting where in- 

 terrupted by occasional drainage courses which have cut below its 

 level. The marked evenness and approximate horizontality of this 

 surface as viewed from the summit of the bluffs, and the apparent 

 absence of residual hills upon it, suggest immediately that it is a 

 surface of aggradation rather than one of erosion or of river plana- 

 tion. Its striking parallelism, so far as the unaided eye may judge, 



