Layered Geology in a Transitional Ecosystem in South Valley Park

The Colorado Front Range foothills put evidence of their underlying geological processes on full display, particularly as visitors go beyond the first elevated ridge delineating the edge of the Rockies, known as the Lyons Hogback. This ridge and the next form a unique valley showcasing rocks of various eras that have emerged during the formation of the Rockies. Due to its unique qualities, the valley has various nature parks created to preserve its natural beauty. South Valley Park, located in the southwestern portion of the Denver suburb Littleton, is just one of many parks in this area open to visitors. This park is a great option for people who are looking for relatively flat, short hikes in the area.

There are two parking lots to enter the park, one in the south and one to the north. Both of these provide easy access for the Coyote Song Trail, which can be done as a loop when combined with the Swallow Trail. This loop is under three miles in distance and the hike can be done in less than half a day. It took me about two hours to complete, but I stopped frequently to admire the surroundings and take photos! Along this loop, you can find massive red sandstone rocks sitting randomly amongst the scenery. These rocks are particularly old extrusions from the Fountain Formation, a set of rock layers that were formed via mineral and organic deposits 290 to 340 million years ago. These rocks are quite plainly distinct from the rocks forming the Lyons Hogback, which are remnants of a newer formation and don’t exhibit the same red rock color. The Fountain Formation also forms the famous nearby Red Rocks Amphitheater and park as well as the Boulder Flatirons.

Throughout this landscape we can also observe a semi-arid plant environment, showcasing a variety of wild grasses, sporadic bunches of shrubs, such as Gambel Oak, often clustered near the red rocks, and Cottonwood Trees near the lowest areas of the valleys. During April when I was at the park, I could see some of these oaks exhibiting marcescence, more colloquially known as winter leaf retention, just as white oaks do on the US east coast! Cottonwoods in particular are only able to grow in areas with frequent water pooling. In such a dry environment, their growth range is noticeably limited. The relative sparseness of the landscape reflects the reliance of the region on nature fire processes to manage overgrowth, though due to the proximity to neighborhoods it’s possible we are seeing higher levels of shrub and tree growth due to unnatural fire suppression methods.

Different critters can be observed throughout the park. While going through the grasslands I observed a mule deer darting between the shrub growths. They often utilize the gambel oaks as a food source. There is a reservoir in the northwest area of the park in which you may be able to observe geese floating on the surface. This particular area of Colorado is also notorious for its rattlesnakes. While somewhat misunderstood as more vicious of a creature than it really is, the rattlesnake may bite humans if it feels cornered, chased, or stepped on. They are venomous, so keep your distance if you observe a rattlesnake and don’t put your hand somewhere where snakes may be living without checking, such as in rock crevices.

As is typical of Colorado, it was extremely sunny and pretty warm on the morning I hiked this park. Sunscreen and water is definitely recommended. The park is also strictly a trail-only park to protect the fragile grasses, shrubs, and especially the sandstone formations, so make sure to stay on the trail. There are restrooms at the parking lots of the trails. There was plenty of space in the north parking lot when I arrived, though it was surprisingly busy for a weekday. I usually encountered another hiker or biker every ten minutes or so on the trail, and unfortunately not everyone cleans up after their dogs so lookout for dog poop as you walk. Definitely recommended for geology enthusiasts!