 Elevations in the forest range from 2 @,@ 800 feet ( 850 m ) in the North Fork Payette River Canyon to 9 @,@ 730 feet ( 2 @,@ 970 m ) at the top of Steel Mountain , a gain of 6 @,@ 930 feet ( 2 @,@ 110 m ) . The forest contains several subranges of the Rocky Mountains , including the Boise , Salmon River , and West mountain ranges . Much of the forest is underlain by the Idaho Batholith , and the forest is dominated by granitic rock , but intrusions of basalt can be found to the west and other volcanic rocks to the south . 
