GEOHERITAGE OF THE WESTERN SAN JUAN MOUNTAINS, COLORADO: CONSERVATION OF AN IMPORTANT LEGACY

The San Juan Mountains comprise a large Oligocene-Pliocene volcanic province in southwestern Colorado whose rich metallic ore veins have produced >$500 million worth of gold, silver, and other important metals since the late 19th century. Geological studies of the region have played an important role in understanding connections between North America Western Cordillera volcanology, hydrothermal mineral deposits, and cultural and touristic development of the American West.

Since the early 1900s, USGS has conducted numerous classical studies of the geology and mineral deposits, resulting in the first identification of a large Cordilleran volcano caldera (the San Juan volcanic “sink”) by W. Burbank (1933). Subsequent geological studies refined understanding caldera formation processes and identified linkage between volcanic activity, hydrothermal activity, and mineral deposition.

Conservation of this unique geological heritage has occurred through a variety of formal site designations: in 1961 the town of Silverton was designated a National Historic District; in 1964 the San Juan Historical Society and the Mining Heritage Center (https://sanjuancountyhistoricalsociety.org/) was established as the principal collection point to archive and educate about the mining history and heritage in San Juan County; In 1989 U.S. Bureau of Land Management and State of Colorado established the Alpine Loop Scenic Byway (https://www.codot.gov/travel/scenic-byways/southwest/alpine-loop) to highlight the close connections between the area’s outstanding aesthetic appeal and links to its cultural, historical, and mining heritage.

These conservation designations have helped raise awareness of the cultural, historical, and geological context for the Western San Juan region and its mining heritage to provide educational framework for visitors and residents alike and can be used together to more comprehensively preserve a region’s geoheritage, especially outside of a National Park Service unit. With no active mining operations in the San Juan region today, the economic lifeblood of the region is linked directly to this geological heritage.