The long red ridge along the foothills is the Dakota Hogback

Driving along the western edge of the Denver area, you cross a steep, narrow ridge that runs north and south for miles. That ridge is the Dakota Hogback, and it marks the line where the Great Plains meet the foothills.

The hogback is made of hard Dakota Sandstone. Long ago this rock lay flat, near the shore of a shallow sea. When the mountains rose, the layers were tilted up on edge. Softer rock around the sandstone wore away faster, leaving the hard layer standing up like the spine of an animal, which is where the name “hogback” comes from.

You can read the landscape from this one feature. The hogback is younger rock than the red and gray peaks behind it, and the tilt tells you the whole stack was pushed up together. Where creeks like Clear Creek and Bear Creek leave the foothills, they cut narrow notches straight through the ridge. Geologists call these “water gaps,” and many roads now follow the creek through the same gap.

The same tilted layers hold the fossils and footprints at Dinosaur Ridge near Morrison. So the ridge is not just a hill in the way of the highway. It is a clear page of Colorado’s geologic story you can see from the car.

For the fossils and tracks on the ridge near Morrison, visit Friends of Dinosaur Ridge, and for the geology in plain terms, see the Colorado Geological Survey.