It turns out that there was volcanism in or near Rocky Mountain National Park, some 25-30 million years ago.
The Lava Cliffs are not quite correctly named. They’re not the remains of an ancient lava flow, but instead are welded tuff, a type of igneous rock formed from pyroclastic fragments that were hot enough to weld together after being deposited. The rock that formed the Lava Cliffs was ejected during an explosive eruption in the Never Summer Mountains, which are about 12 miles to the west. The range of colors in the cliff face suggests that it was formed from rhyolite, a silica-rich rock that produces very viscous lava.
My older son was not particularly perturbed by the ancient eruption, and since we were not immediately threatened by local volcanism, he thought the Lava Cliffs were cool.
We had now passed the highest point in the park and were approaching the Kawuneeche Valley, the upper reaches of the Colorado River. I had a personal project to fulfill in that regard….