Carbon Mountain, just south of Durango, has long been a center of activity. One of the largest Pueblo I communities in the region was located near it in the 8th century. In the 1930s, the mountain -- part of the Hogback Monocline -- garnered national attention when it "erupted," possibly due to methane coming into contact with underground coal seam fires. Now it looms over Lake Nighthorse, and has hydrogen sulfide and methane seeps at its base.
Jonathan P. Thompson 