South San Juan Wilderness, Colorado

Maybe not as famous as the larger Weminuche Wilderness, the 158,790 acre South San Juan Wilderness of the Rio Grande and San Juan National Forests offers of 180 miles of trails, including 42 miles along the Continental Divide. This page offers a map and GPS tracks of the entire wilderness. The links below offer maps two different hikes that will introduce you to the splendors of the area.

Conejos Peak Loop (aka South Fork-Roaring Gulch Loop). Situated in the south east corner of the wilderness, this 22.2 mile hike in the Conejos Peak (pronounced coe-NAY-hoes) area offers a mix of wooded valleys, alpine meadows and huge herd of elk.

Blue Lake Loop. Entering from near Platoro Reservoir the this 17.7 mile hike offers scenic Blue Lake, a stretch of the Continental Divide Trail and Conejos Falls.

The Map of the Wilderness: This map is FREE, but first, be advised that it is a 25 mb file, so you will need a fast connection and some patience. The map is true 1:24,000 scale based on the USGS 7.5 minute quadrangles. The featured trips are shown in red and are based on the GPS track taken on the hikes. The trails in blue and purple are other trails in the area. The purple trail is the Continental Divide Trail. Green depicts unmaintained trails such as to the top of Conejos Peak. The green and black line is the wilderness boundary. The forest roads are in black and based on aerial and satellite imagery. Some may not be drivable with low clearance cars so check with the FS to make sure you can get to your trailhead. Selected camp sites, including the ones we used, are green “^”.

All the tracks but the ones in red are from the Forest Service GIS database (there is more on this source at the bottom). For the most part there was very good correlation between the our GPS tracks and the forest service’s version. I also compared the FS tracks to the National Geographic Trails Illustrated map and conclude the FS tracks are definitely good enough to plan your trip and are probably the most accurate publicly available rendition. Whereas many of the tracks were right on, there was a significant difference between the FS version of the El Rio Azul Trail (718) and what we collected. The good news is that both start at the same place and end at the same place, with the difference being the actual route. My guess is the trail was re-routed since the FS track was taken. There may be others, but as I mentioned above, most are correct and all can be used for planning.

Since this map is so big, my suggestion is to use the Trails Illustrated map to pick your trip and use this USGS topo with track data to refine it. Since I am obviously a map guy, I would then print the sections of the big USGS topo for the field. You will note on the next pages I'd be more than happy to sell you weatherproof versions of the hikes listed above ($5/sheet plus S&H on 11x17 Rite in the Rain stock), but they are formatted so that you can download and print them yourself.

Tracks of the Entire Wilderness: This link is to a Google Earth KML file for all the tracks on the big map. You should be able to right click the file and save it on your computer. Then open it with Google Earth to see the entire wilderness trail system in interactive 3-D. Once in Google Earth you can access individual tracks. If you have the right software you can select the tracks you want and load them on your GPS. Here is a GPX version of the same set of tracks.

Background: The San Juan Mountains are one of the largest distinct mountain systems in the US. They stretch from the San Luis Valley on the east side to beyond Durango and Telluride on the west. The northern edge extends to Highway 114 west of Sagauche (sa-WACH) and the south end approaches Highway 160. The mountains boast seven wilderness areas including the Weminuche, South San Juan and La Garita. They also have the popular Durango Silverton narrow gauge railroad that skirts the west side of the Weminuche. It is well known to backpackers because it will drop them off at Needleton for a hike to the Chicago Basin and the Needle Mountains. There is another narrow gauge railroad in the area. The Cumbres & Toltec Narrow Gauge Railroad runs through the Rio Grande National Forest from Chama, New Mexico to Antonio, Colorado, one of the access towns for this hike.

On the subject of access towns, we've spent several days on various hikes in the San Luis Valley to check out the Great Sand Dunes National Park (video), imbibe at the San Luis Valley Brewery in Alamosa, take the train from Alamosa to La Veta Pass for the Rails to Ales brew fest and do a little rock climbing in the Rock Garden. Great Sand Dunes is a pretty amazing. Thousands of acres of dunes up to 750 feet high blowing up against the flank of the Sangre de Cristo Range. It is pretty popular so expect a crowd on a nice day, many of them playing in Mendeno Creek on their way to the dunes. Back country camping is allowed.

Though the brewery and restaurant appears to do a brisk business, we found the beers a little disappointing. With all the high quality micro brews in Colorado, we had high hopes. San Luis beers tend to lack the bold flavor of a good microbrew and tend to be on the flat side. The upside is you could drink them like Mai Tais at a luau (been there, done that) and make your walk back to the motel as difficult as a 5.6 pitch. The down side is that if you are a beer snob (guilty) and are looking for rich taste and subtle flavors, their collection was lacking. We liked the IPA best but it only had the hoppiness of a pale ale.

Rails to Ales is a kick. Pick up the train (video) in Alamosa, ride two hours across the valley and up to Fir, Colorado (which is nothing but a railroad spur in an alpine meadow (video) (near 10,000 feet) and a band stand. When we were there in 2010, they had about 20 breweries, about 80 different beers, BBQ and brats. The music was hokey but a good time was had by all. A two hour train ride back with restaurant service meant no problem with that long drive home.

Geology: The rocks in the San Juans date back to the 1.7 billion year old granites and gneisses found northeast of Durango but they are dominated by Tertiary volcanics. The formation of most of the Rocky Mountains began in the late Cretaceous, 70 to 80 Ma (million years ago), and ended during the Eocene about 35 Ma during a period called the Laramide Orogeny. The mountains were formed when the continental mass of the western US was compressed as it over rode the Farallon plate, an ancient tectonic plate of the Pacific Ocean. The tectonic forces at work upthrusted (a type of steep angle fault) billion year old basement rock thousands of feet above sea level to form the Front Range, Sangre de Cristos, Sawatch (including Mt Elbert and the Collegiate Peaks), Mosquito, Wind Rivers, Uintas, Black Hills and many other Rocky Mountain ranges. One of the key field characteristics of these ranges are massive outcrops of Precambrian granites and gneisses. The presence of these older rocks in the Needle Mountains northeast of Durango indicate a Laramide source of this part of the San Juan range.

Something happened at the end of the Laramide to cause a change in the configuration of the tectonic plates underneath the Rockies. Maybe the continental plate overrode a spreading axis on the Farallon plate or maybe a broken slab of the Fallon Plate buoyed up the western US, but whatever it was it changed the tectonic forces from compression to crustal extension (it began to pull apart). About 35 Ma, and in response to this pull-a-part tension, numerous volcanic centers formed. In the San Juans, andesitic lava ( andesite is a fine grain intermediate composition volcanic rock) and ash spewed from stratovolcanos (similar in form but not related to Mt Rainier and Mt St Helen) forming the Conejos formation. On the drive up FR 250 from Highway 17 to Platoro, thick layers of reddish andesite lava forms the cliffs that cap the sides of the canyon walls. There are several places on the Roaring Gulch loop where ashfall conglomerates can be seen. They look like sedimentary conglomerates with cobbles bigger than softballs but the matrix is the fused glass of a tuff or ignimbrite.

This was just the beginning of the volcanic activity. By about 29 Ma, activity shifted to eruptions of large volumes of firey ash from a minimum of 14 calderas. Think of 14 Mt St Helen, with some on a much grander scale. By the time all was said and done, there were about 10,000 cubic miles of ash deposits covering the area of the present day San Juans. One of the best places to see these deposits is in the La Garita Wilderness at the the Wheeler Geologic Area where a minimum of 3 separate ash flows from the San Luis Caldara are dissected into badland topography.

The extent of this volcanic activity is continental, supporting the play of plate tectonics in this event. A complex series of Tertiary volcanic episodes along the east margin of the North American plate stretch from Mexico’s Sierra Madre Occidental volcanic field and to the Lowland Creek field of Montana (the source of Montana’s alluvial sapphires). Included in between them are noted hiking destination such as Gila Wilderness (Mogollon-Datil field), east Yellowstone and the Absaroka-Beartooth Wilderness (Absarokas field), southern Frank Church/River of No Return (Challis field) and Big Bend (Trans-Pecos field).

The tension continued for several million years until about 26 Ma when the character of tectonic activity changed again. The violent and explosive volcanism stopped and was replaced predominately by basaltic lava flows associated with the Rio Grande Rift. The influence of this phase can be seen in the localized outcrops of basalt within the San Juans and more evidently by the huge rift valley adjacent to the eastern edge of the range, the San Luis Valley.

Ecosystems: Moving away from the geology, the San Juans are dominated by four ecosystems. The Alpine Zone occurs above 11,000 feet and is characterized by open alpine meadows and sparse and stunted Engleman spruce, subalpine fir and limber pine. The most prevalent zone is the Volcanic Subalpine Forest occurring between 9,000 and 11,000 feet. It occurs on the volcanic rocks and is characterized by Engleman spruce, Colorado blue spruce and aspen. We also saw a lot of lush corn lily (AKA false hellebore) in the under story of some of the aspen groves. In the Needle Mt areas, between 9,000 and 11,000 and where the underlying rock is granite and gneiss is the Crystalline Subalpine Forest. It has the same suite of trees as the Volcanic Subalpine Forest. The fourth eco-zone is less prevalent but is traversed on the road to the trailhead. The Volcanic Mid-elevation Forest is similar to it’s subalpine cousins but with occasional lodgepole pines, ponderosa pines and Douglas firs.

Forest Service Database: When I originally created these maps I was able to tap into several external databases. Since that time most have been changed so if youwant the sources data you will need to do some searching yourself.

--The Rocky Mountain Region (Region 2) has a Geospatial Library with Datasets by Forest Unit. This has trails in both ESRI shape files (ArcGIS) and Google Earth KML files. It also has roads, administrative areas and recreation sites. Of special note are the zoomable Visitor Maps. These are the green general Forest Service maps that have road designations, trails, streams and administrative features but no topo lines and a small scale (1/2 inch per mile).

--Another source is the FS Geodata Clearinghouse, Vector Data Gateway. This one is map-based and once you find the layer tab on the right is fairly straightforward to use. The files are ESRI shape files so you will need and Arc product or a shape file interpreter. I had a link here before but it no longer functions so you would need to search for it.


Weatherproof Topographic Maps at - Hiking Trails of the Ouachitas and Ozarks
Featured Topographic Maps in Oklahoma and Arkansas
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