Red Rocks Park and Amphitheatre sits on the west side of the Denver metro area near Morrison, Colorado. If you take I-70 west, you can also check out the I-70 road cut as well. Both areas showcase the stunning geology of the foothills.
Throughout its history of weathering, the rocks have gained their characteristic pink-red color from iron oxide minerals and iron-rich groundwater flows in the area.
Geological Highlights
The Great Unconformity: Start your visit to Red Rocks by driving or biking up to the uppermost parking lot to check out The Great Unconformity.
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The Unconformity is between the Fountain Formation (300 million years old) and the Proterozoic gneiss (1.7 billion years old), representing a 1.4 billion-year gap in time.
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Don’t worry, there is a placard showing you where this is.
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If you see people with their hands on either side taking photos, chalk them up as geos! My kids still don’t understand why this is so cool to me, but maybe someday they will!
The Fountain Formation: The Fountain Formation is composed of coarse-grained sandstone and conglomeratic alluvial fans deposited from erosion off the ancestral Rockies. This formation was then uplifted during the Laramide Orogeny.
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Within the Fountain, you see a combination of sandstones along with various conglomeratic units.
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Make sure to look left and right of the amphitheater stage, and you can really see the different grain sizes and erosional story.
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You can also see how steeply the beds are tilting. Take a walk or run up the stairs to actually feel how steep the tilting is. 😊
Other formations: Additional units older than the Fountain Formation and making up the Front Range (the Lyons, Morrison, and Dakota formations) can be seen by walking the road around Dinosaur Ridge or on the bike trail through Morrison headed toward C-470.
Dig deeper: Learn more about the geology on the park's website. I'd also recommend this book by Robert J. Weimer and L.W. Le Roy entitled Paleozoic-Mesozoic Section: Red Rocks Park, I-70 Road Cut, and Rooney Road, Morrison Area, Jefferson County, Colorado.
