Introduction (Unit 1) - Eocene Florissant
The uplift of the Rockies had began during the late Cretaceous and by the late Eocene, the region had low to moderate relief. During the late Eocene (36.7 million years ago), volcanic activity increased, beginning with an enormous eruption near present-day Mount Princeton. This eruption blanketed the area with the Wall Mountain Tuff as far away as 150 kilometers (93 miles). Imagine a superheated cloud of ash, rocks, mineral crystals, glass, and debris moving at speeds of up to 100 miles per hour. Two million years later, near the town of Guffey, Colorado a cluster of large stratovolcanoes developed sending ash and lahars into the area. It was this highly active volcanic period that helped to create the ancient Lake Florissant.