sentences:  primarily through rivers cutting deep valleys through the igneous and sedimentary rocks.The geologic boundaries of the coast range formation extend from southwest Washington state in the north to around the Coquille River in the south where the older and taller Klamath Mountains begin.In the east the mountains begin as foothills forming the western edge of the Willamette Valley and continue west to the coastline and beyond where the basalt formation tapers off into the continental shelf and ends at the continental slope with several banks and basins off shore.