Redcloud and Sunshine Peaks are 14ers (peaks over 14,000 feet) in the remote San Juan Mountains in Colorado. These are among the largest (by area), most varied and, one can argue, most scenic mountains in the state. Volcanism in this area began about 35 million years ago, with the eruption of dark lava from several dozen volcanoes scattered throughout the region. These volcanoes may have resembled the active volcanoes in the present Cascades range in the states of Washington and Oregon, which are built of lava flows and explosively ejected volcanic debris.
So, where are the volcanoes in today’s landscape? They got wiped off the map because a “supervolcano” destroyed them a few million years later. The eruption, 10,000 times more violent than Mount St. Helens and possibly the largest single eruption in history, produced enough lava and ash to fill Lake Michigan. This explosion left behind the La Garita Caldera, a gaping hole twice the size of Los Angeles, as the supervolcano emptied and collapsed into itself. Remnants of the volcanoes that remained were either obliterated during the eruption or were covered with ash more than 4,000 feet deep in places.
The eruption of the Lake City caldera about 23 million years ago marked the end of the explosive caldera-forming volcanic activity in the region. The caldera itself is almost completely filled in with tuff (consolidated volcanic ash) and breccia (type of rock made of broken fragments of volcanic material cemented together) formed from collapse of the caldera walls. Redcloud and Sunshine Peaks are both carved from this tuff. As for the striking red color on the summit of Redcloud and along the trail to Sunshine? It may remind you of Mars. The oxidation (rusting) of iron in the rocks produces the reddish hue.