GLACIAL BORDER OF SPOKANE 
359 
GLACIAL BORDER OF SPOKANE 
By Prof. Thomas Large 
Spokane, Washington 
Notwithstanding the fact that Glacial phenomena abound on 
every hand throughout northeastern Washington their discription 
and explanation are quite generally neglected. Before attempting 
portrayal of any phase of these features their geological setting 
is with advantage a theme of brief outline. Weaver, in describing 
the adjacent county of Stevens, regards the tract as a southward 
extension of the Pend Oreille Mountains and the Spokane Plateau; 
the first referring to that uplift in northeastern Washington lying 
between Clark Fork and the Colville and Chamokane rivers, and 
the latter to the basaltic plain which continues southward from the 
lava fields of the Columbia River. If this classification be followed 
it should be realized that the mountains mentioned constitute two 
distinct epochs of uplift. The northernmost section, which has re¬ 
ceived most attention from geologists, is mainly composed of meta- 
morphic rocks, argyllites, slates, indurated shales and limestones, 
which are variously assigned to dififerent divisions of Paleozoic 
time, even so late as the Carbonic Period. 
To the south, in an almost equilateral triangle, of approximately 
80 miles on a side, having its eastern border a few miles beyond 
the Idaho boundary, and extending from Clark Fork to the Tekoa 
Mountain, and with its western apex near Davenport, is a region 
which seemingly shows no evidences of marine submergence since 
Pre-Cambrian times. This supposed ancient upland is highest at 
its eastern border and slopes gently to the southwest, until it dis¬ 
appears beneath the Columbia River basalts, at an elevation of 
about 2500 feet. Its surface is not a uniform plain, but is carved 
by streams and moulded by weathering into ridges and peaks. 
