If you were standing in this area 36.7 million years ago, you would have been the victim of a widespread cataclysm: every living thing being incinerated in an instant by a glowing cloud of superheated incandescent gas and volcanic rock debris traveling at enormous speed originating from the Sawatch Range to the west.
The evidence of this natural disaster is a hard, tan to grey rock known as the Wall Mountain Rhyolite, scattered on this hillside. Rhyolite is a light-colored volcanic rock, typically containing high temperature minerals such as the feldspar sanidine. Small rod-like crystals of sanidine can be seen on fresh broken surfaces of this rock. The path of destruction would have generally followed the contours of the landscape at that time, the valleys being “ground zero” and the highest hills possibly a safe-haven. This event impacted as far northeast (37 miles) as Castle Rock, where similar rocks of the same age have been found.
Two million years later, the Florissant Formation, containing well-preserved plant and insect fossils from a much warmer and wetter climate than today, was deposited in a large lake in the valley before you (including the Florissant Community Park field to the south). This natural lake was dammed by a low-temperature mud flow which can be seen today near Evergreen Station on CR1. It was sourced from one or more volcanoes in the Guffey area 18 miles southwest.
The wide valley to the south and west is part of the Florissant Fossil Beds National Monument. This valley is probably where the Spanish army encamped in 1779 while on a campaign against the Comanche. They were led by 200 Ute warriors/scouts. The Ute Indians referred to the Fossil Beds as “Valley of the Shadows.” This referred to the 35 million-year-old fossils entombed in the ash by the Guffey volcano. It was thought that the shadow of the plants, insects and animals held their spirit.