In the Willamette Valley the soils are mostly clay loams, of a basaltic nature on the foothills and greatly enriched in the river bottom lands by washings from the hills and by deposits of rich black humus.
Above Deir, where lie the ruins of Halebiya, the river breaks through a basaltic dike, el-I;Iamme, some 300 to 500 ft.
Deep, with steep walls of basaltic and kindred rocks.
The spurs consist in some cases of white chalk covering the limestone, and on the south there are several basaltic outbreaks.
On the plateau itself the sandstone is generally overlaid by the Deccan trap, a blackish-coloured basaltic rock of volcanic origin, the high level tableland having been formed by a succession of lava flows, the valleys of Central India being merely "denudation hollows" carved out by the action of rain and rivers.