THE SPOKANE GLACIATION 585 



stream gravel, ^or was the Mica channel eroded to any extent. Prob- 

 ably pondcvi waters were backed up from the south until the last stages 

 in erosion of the Xorth Pine Creek channel. 



Vicinity of Cheney. — Cheney lies 15 miles southwest of Spokane and 

 ]0 miles northwest of Spangle. About this town are recognizable the 

 same elements in the topography as already outlined — the higher pre- 

 basalt hills, the Palouse type of maturely dissected hills, and the lower 

 scablands. The scablands have less relief than either of the other ele- 

 ments, but are much rougher. They are commonly a maze of minor 

 channels and depressions eroded in the basalt. 



Cheney lies at the head of the largest tract of scabland on the pla- 

 teau — a tract which extends from Spokane River to Snake River. It is 

 not uninterruptedly scabland, however. It contains isolated groups of 

 Palouse Plills. One of the largest of these groups lies immediately north 

 of Cheney and has an area of about 13 square miles. Many of them are 

 not a square mile in area. In topography and in soil, these tracts are 

 identical with the Palouse wheat country to the east and southeast; but 

 the gentle, concave lower slopes of maturity, so characteristic of these 

 hills, is absent on the peripheries of the isolated groups. Instead, these 

 outer slopes are much steeper and are generally convex. They meet tlie 

 roughened plain of the scabland with a definite angle. The bounding 

 slopes clearly are much younger than the valley slopes among the hills. 



The hill groups are elongated northeast-southwest, in harmony with 

 the elongation of the channels on the basalt surface and with the scab- 

 land tract as a whole. In many of these linear groups there are longi- 

 tudinal valleys, not of the mature typo, but with steep sides and scabland 

 floor. All such valleys pass completely through a hill group, leading 

 from the rocky plain into the rolling hills and out again to the plain. 



Another feature of this great scabland tract is the presence of many 

 widely scattered granite boulders. T^owhere (with one exception, to l)i' 

 detailed later) has this foreign debris been found back among or on t\i:' 

 slopes of the hill groups. Associated with it, but much less common, 

 are terraces of gravel composed largely of basaltic debris, but witli 

 granite and other foreign material distributed through it. Sncli deposits 

 commonly lie on the southwest sides of rocky slioulders or hills in tbe 

 channels. They have been opened for railroad ballast and road metal at 

 many places over the whole scabland area. 



From a survey of the patches and groups of the Palouse Hills scat- 

 tered over the scabland plain south of Cheney, it seems clear that thev 

 are but remnants of a once continuous cover of the basalt, and that the 

 scablands have resulted from removal of the Palouse Hills bv erosion in 



