The San Juan Mountains are my favorite mountain range in Colorado. They are not the highest mountains in the state, though with six peaks surpassing 14,000 feet (4270 meters) in elevation they’re close. It is the largest range in Colorado by area. They slice spectacularly through the southwestern part of the state, forming a stunning Rocky Mountain landscape.
The major towns bordering the San Juans are Durango, Montrose and Alamosa. Telluride, Creede and Silverton are smaller towns with historic, touristic and recreational personalities. Hiking, mountain climbing & biking, horse-riding and white-water rafting are very popular, as are 4WD jeep rides. There are four ski areas in the range, with Telluride being by far the biggest and most famous. There are a plethora of summer homes and ranches, many owned by wealthy people. Some are even famous (Tom Cruise is one).
William Henry Jackson, a photographer’s photographer
An intrepid photographer named William Henry Jackson, whom many of you might already know about, trekked through this range on his mission to document the best of the rugged American West in the late 1800s. As part of the Hayden Expedition, he used pack animals and his own strong back to lug his large-format camera (complete with huge glass plates) up and down these steep mountains.
He set up make-shift tents that served as darkrooms, developing his prints often on the very summits of the mountains. All in all he made about 300,000 black and white pictures. These images, reproduced in newspapers in cities worldwide, played a large part in forming an idyllic image of the American West in the minds of those looking for new opportunity. The call of “Go West young man!” now had superb pictures to go with it, and the mass migration soon followed!
The San Juans are a large western branch the Rocky Mountains. Like the rest of the chain, they formed by the uplift and buckling of a large pile of older sedimentary and volcanic rocks during the late Cretaceous (the dinosaurs went extinct at the end of the Cretaceous, 65 million years ago). This massive crustal “squish” happened because of a collision between two huge chunks of Earth’s crust: the Pacific and North American Plates.
Some of the highest and most rugged peaks in the San Juans are made of very hard igneous intrusions (granite is an example) that resist erosion. These so-called plutons were intruded as the mountain building process got going. Many of the flat-lying layers of sedimentary rocks forming the canyon walls of the adjacent Colorado Plateau lap up onto the San Juans. There they take on a different look, being strongly deformed by folding and faulting.
Hard sedimentary rocks like quartzite, which is metamorphosed (heated and changed) sandstone, form prominent peaks and cliffs because quartzite is hard like the plutonic intrusions. Other sedimentary rocks, such as the mudstones and sandstones of the dinosaur fossil-bearing Morrison Formation, typically form the rubbly slopes bordering the peaks. Many valleys and canyons follow faults. Ouray, Colorado lies at the base of a steep grade because of the E-W trending Ouray Fault.
Volcanism is one other important force that helped to form the San Juan Mountains. Large and explosive volcanoes erupted in middle Tertiary times (about 30 million years ago). Many calderas, including the Silverton Caldera, make up what’s called the San Juan Volcanic Field. Calderas are bigger than craters and are formed when the volcano violently explodes and collapses back into its emptied magma chamber.
You can see these volcanics (tuffs – rock from volcanic ash and lavas) by driving up and over spectacular Red Mountain Pass. In the San Juans, the colorful volcanic rock forms high but more rounded peaks that are less rugged than those formed by earlier igneous intrusions of the main mountain-building event.
Thar’s Gold in them thar hills!
In the late Tertiary, from about 20 to 10 million years ago, the slowly cooling granitic intrusions that were the sources for those explosive volcanoes sent forth gold and silver-bearing fluids into the faults and fractures of the calderas. So like so many mountainous regions of the world, the events that formed valuable mineral deposits were the penultimate phases of the mountain-building process, the last gasp of the big granite bodies solidifying deep underground.
In southwest Colorado as in similar places throughout the world, these events dictated the much later human history of the area. The mining history of this area, while interesting, also has a dark side. The Summitville Mine in the eastern San Juans was worked by the old-timers in the late 1800s, well before modern environmental regulations.
The pollution from acid drainage resulted in the Environmental Protection Agency (EPA) declaring the area a Superfund site. They have been trying to clean it up since the 1990s. The EPA wanted to list an area near Silverton for Superfund status, but local opposition forced them to drop the idea and rely on the mining company to help control acid drainage. The local economy relies heavily on tourism, and residents did not want that reputation tainted.
The San Juan Mountains, a real Rocky Mountain wonderland, make for outstanding landscape photography. In early summer there are spectacular wildflower displays. In autumn the aspens turn gold beneath the snow-dusted peaks. If you have never been to this part of Colorado, I recommend making every effort to visit sometime soon. And don’t forget your camera!
Click on any of the images to go to my image galleries. They are all copyrighted, so aren’t available for free download without my permission. If you’re interested in purchase of fine-art prints or high-resolution downloads please contact me. Thanks for reading and have a great day!