The most common rock type in this area is intrusive igneous, which are highly fragmented granitics, this includes most of the Foss Lakes and Enchantment Lakes area. The other major rock types are sedimentary, metamorphics, ultrabasic rock complex and the extrusive igneous group that include basalt, andesite, and rhyolite. The metamorphic rocks are primarily in the northern part and the southern area is made up of volcanic and sedimentary rocks. The Wenatchee Mountains are mostly composed of peridotite.