The west slopes have been eroded by glaciation and water down to the granite bedrock which has created a dramatic contrast between the volcanic and the granitic landscapes. The wilderness protects habitat for a great variety of plants and animals especially on the slopes of Round Top, which is designated a special interest area. Plants include Ponderosa pine, canyon live oak as well as alpine vegetation of Whitebark pine, subalpine fir, and western juniper, with western white pine, mountain hemlock, and lodgepole pine found in sheltered areas. Waterways such as the North Fork of the Mokelumne River have riparian zones of white and mountain alder, creek dogwood, western azalea and bitter cherry. Wildlife include the black bear and mule deer, as well as martin, bald eagle and the California spotted owl.
Areas of special interest
The Round Top Botanical Area is at the junction of three botanical provinces and includes red fir forest, sagebrush scrub, subalpine and alpine environments. The combination of soil types, varying exposure and elevations produce diverse plant life, such as the phantom orchid, a rare parasitic plant. The plant's common name is due to its color being all or mostly white. The Round Top Geologic Area has more than within the wilderness and encompasses a variety of geological areas, including exposed granodiorite, lava flows, dikes, glacial moraines and cirques. The landform known as Elephants Back is a rounded mass of solidified lava. Mineralization produced gold-bearing quartz veins, and relics of past gold mining activities are still present in the area.
Recreation
The Mokelumne Wilderness has a variety of recreational opportunities all year. With landscapes ranging from deep canyons to alpine heights and more than two hundred ice-scoured lakes and tarns, fishing and hiking are popular activities as well as cross country skiing. Access is from roads surrounding the wilderness boundary with Carson Pass being the most used entry point. The Pacific Crest Trail, the Tahoe–Yosemite Trail and the Emigrant Summit Trail all cross through the Mokelumne Wilderness. The Emigrant Summit Trail is a designated National Recreation and Historic Trail that follows the western boundary and then passes through the wilderness from Emigrant Valley to Caples Lake. Wilderness permits are required year-round for overnight visits.
