To many, the most outstanding natural features of Colorado National Monument are the park's geologic formations. In each of the canyons, visitors can see the remarkable effects of millions of years of erosion on a landscape of sedimentary rock.

Two unusual natural features are common in Colorado National Monument and intrigue both scientists and visitors: biological soil crusts and potholes.

Have you noticed the bumpy, knobby, and sometimes dark soil along the trails? That’s biological soil crust! Just like a coral reef is formed over time by lots of small organisms living together, soil crust is formed the same way. Moss, lichen, green algae, cyanobacteria (sigh-AN-oh bacteria), and microfungi all work together to hold sand grains in place and create an environment where seeds can grow. Biological soil crust is extremely slow growing; a footprint can erase decades of growth. You can help protect biological soil crust by staying on established trails. Don’t bust the crust!

Potholes are naturally occurring basins in sandstone that collect rainwater and wind-blown sediment. These potholes harbor organisms that are able to survive long periods of dehydration, and also serve as a breeding ground for many high desert amphibians and insects. Both of these communities are very vulnerable to human impacts.