[citation needed] They span the northwestern portion of the Golden Valley Wilderness, which sits between it and the Almond Mountains on the southeastern side.

[3] The mountain range is cut by several deep-walled canyons with distinctive layers of multicolored sedimentary rocks.

[2] The pre-Tertiary rocks in the area mainly consist of quartz monzonite.

[2] The major sedimentary unit is the Bedrock Spring Formation, which is chiefly composed of arkosic sandstone and conglomerate, as well as some silstone and brecciated volcanic rocks.

[2] Overlying these are flows of Lava Mountains andesite dating to the late Pliocene, which are finally covered by Quaternary gravels, alluvium, and travertine.