The Great Dikes of Spanish Peaks Country formed during the same period of volcanic activity as the Spanish Peaks, Mt. Mestas, and Silver Mountain.

These vertical granite formations were formed by molten rock several thousand feet underground, below and among many layers of sedimentary rock. Over time, the ground rose and the softer rock eroded away, exposing these igneous intrusions.

Spanish Peaks Country has three unique sets of dikes. One emanates radially from the West Spanish Peak, another set emanates radially from Silver Mountain, and a third set crosses the landscape roughly 80 degrees east of north.

The dikes in this third set are roughly parallel to one another, are the longest and oldest of the dikes, and were formed around the same time as the Sangre de Cristo Uplift—the event that pushed up the Sangre de Cristo Mountains 27 million years ago.

Spanish Peaks Country’s dikes are granite. In the western portions of Las Animas and Huerfano Counties, there are some uplifted stone walls of the Dakota Formation. They look like granite but are actually compressed, durable sandstone parts of a formation running from Canada to Mexico along the Front Range and eastwards.