Weminuche Wilderness

The Weminuche Wilderness is a wilderness area in southwest Colorado managed by the United States Forest Service as part of the San Juan National Forest on the west side of the Continental Divide and the Rio Grande National Forest on the east side of the divide. The Weminuche Wilderness was designated by Congress in 1975, and expanded by the Colorado Wilderness Acts of 1980 and 1993. It is located 4 miles (6.4 km) southeast of the town of Silverton, 17 miles (27 km) northeast of Durango, and 8 miles (13 km) west of South Fork. At 499,771 acres (2,022.50 km²), it is the largest wilderness area in the state of Colorado. Elevation in the wilderness ranges from 7,700 feet (2,300 m) along the Animas River to 14,093 feet (4,296 m) at the summit of Windom Peak.

The Weminuche Wilderness is dissected by a narrow north-south corridor within the Animas River Gorge through which the Durango and Silverton Narrow Gauge Railroad travels between Silverton and Durango. To the west of this corridor are the West Needle Mountains. To the east lie the Needle Mountains and the bulk of the wilderness. Two train stops within the gorge allow hikers access into the Needle Mountains.

The Wilderness was named after the Weminuche Native Americans.

The surface geology of the Weminuche Wilderness is characterized by two geologic provinces. The western third of the wilderness is within the Needle Mountains Proterozoic complex while the remainder of the wilderness is within the San Juan volcanic field.

The Laramide Orogeny, which began approximately 80 million years ago in the Late Cretaceous, resulted in significant regional uplift. A dome 100 miles (160 km) wide lifted rock more than 10,000 feet (3,048 m) in the western third of the wilderness. Pushed up were Proterozoic igneous and metamorphic rock and overlying, younger Paleozoic and Mesozoic sedimentary rock, as well as Cenozoic volcanic rock. Erosion has removed the overlying rock and today the Proterozoic rock is exposed, forming the high, jagged, Needle Mountains. The highest peaks in the wilderness are in the Needle Mountains. These peaks include three fourteeners: Windom Peak, Mount Eolus, and Sunlight Peak. Eolus granite is a common rock in the Needle Mountains and these fourteeners are composed of this intrusive igneous rock.

To the east lies the San Juan volcanic field. While this region was also uplifted during the Laramide Orogeny, additional mountain building occurred as Tertiary volcanism deposited lava and ash, which in some places was over 6,000 feet (1,829 m) thick. These volcanic rocks overlay Cretaceous sedimentary rock, which is exposed in only a few places on the southern edge of the wilderness.

The Weminuche Wilderness was glaciated during the Pleistocene and the current landscape is dominated by glacial landforms including horns, arêtes, cirques, tarns, moraines, and U-shaped valleys.

At lower elevations, particularly along the southern side of the wilderness, are montane forests with stands of ponderosa pine and Douglas fir and thickets of Gambel oak. Higher and widespread through the wilderness are subalpine forests dominated by Engelmann spruce and subalpine fir. Stands of aspen occur in the wilderness on historically disturbed sites in both the montane and subalpine zones. Above tree line, which in the wilderness is at an elevation of about 11,500 feet (3,500 m), is alpine tundra dominated by grasses and forbs, along with extensive thickets of willow.