[6][7][8][9] The Laramide Orogeny, which began approximately 80 million years ago in the Late Cretaceous, resulted in significant regional uplift.

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.

[5][6][7] 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.

[5] 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.

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.

There are concerns over the environmental impact of these non-native goats, particularly their harm to native bighorn sheep populations.

There are nearly 500 miles (800 km) of interconnected trails in the wilderness, which provide for multiple options for both day and multi-day trips.

Two of these trailheads are the Needleton and Elk Park stops on the Durango and Silverton Narrow Gauge Railroad, which provide the most direct access to the highly visited Needle Mountains.

Chicago Basin sees approximately 10,000 visitor use days each year, most seeking to climb one or more fourteeners, and the area can be crowded.

Environmental impacts have resulted in use restrictions in the Chicago Basin area that go beyond regulations applied to the wilderness as a whole.

The trail then weaves northwest 83 miles (134 km) through the wilderness to Stony Pass on San Juan County Road 3 near Silverton.

More common are long stretches across alpine tundra, rocky slopes and ridges, and subalpine meadows.