Cochetopa Dome is an 11,138-foot rhyolitic lava dome in Colorado’s San Juan Mountains within Gunnison National Forest. Rising from the Cochetopa caldera, it formed about 27 million years ago when lava was extruded into one of the San Juan volcanic field’s collapsed volcanoes. The caldera, about 20 miles wide, underwent as much as 2,600 feet of vertical subsidence and remains one of the region’s clearest and most recognizable calderas because later volcanism disrupted it less than many others. Its geology is still plainly visible in the contrast between the grassy, shrubby caldera floor and the forested rim and dome, with erosion and limited drainage helping preserve the basin’s form.