The stone walls radiating from the Spanish Peaks are famous volcanic dikes

If you spend time in the high country around the Spanish Peaks, you will notice long, narrow walls of rock that run across the land like the spokes of a wheel. These are radial dikes, and they are one of the best-known geologic sights in southern Colorado.

A dike forms when molten rock pushes up into a crack in older rock and cools there into a hard sheet. Around the Spanish Peaks, many such cracks filled and fanned outward from the peaks. Over a very long time, the softer rock around the dikes eroded away faster than the dikes themselves. What is left standing are stone fins, some tall enough to look like ruined walls built by hand.

You do not need any special gear to appreciate this country. The Highway of Legends scenic byway travels through it, and the dikes are part of what makes the landscape around the peaks so distinctive. The geology here is striking enough that the Spanish Peaks carry a National Natural Landmark designation, a federal recognition of outstanding natural features.

For the real geologic story, including how dikes form and why these ones still stand, the Colorado Geological Survey and the National Park Service’s National Natural Landmarks program are good places to start.