About 300 million years ago, the land was uplifted creating the ancestral Rocky Mountains.[55] Fountain Formation was deposited during the Pennsylvanian period of the Paleozoic era, 290–296 million years ago. Over the next 150 million years, the mountains uplifted, continued to erode, and covered themselves in their own sediment. Wind, gravity, rainwater, snow, and glacial ice eroded the granite mountains over geologic time scales.[56] The Ancestral Rockies were eventually buried under subsequent strata.[57]
The sun made us lazy, and after following Brian as he made his way upstream I found a wider expanse of sand and gravel, promptly plopping down on a pair of flip flops I had brought in my backpack as a make-shift seat. After identifying the northern harrier hawk over my head, and the savannas sparrows and red-winged blackbirds perched precariously on reeds across the water, I took out my knitting project. I didn’t have to worry about losing Brian; in the valley I could see for miles in both directions.
