Igneous Rocks

Igneous Rocks:

This weekend I decided to go visit one of my favorite places in Colorado, Red Rocks amphitheater. It was formed over 300 million years ago. The first time I saw this rock formation it instantly brought me back to my childhood days of watching old western movies. The rocks just reminded me of a canyon a cowboy would seek shelter in. The red rocks point upwards to the sky in a spectacular display. Considered an early version of the Rocky Mountains or ancestral Rockies, they rose and shed their gravelly sediment in the oxygen rich atmosphere of Pennsylvanian times. 

The color is what caught my attention the most, rich with iron oxide and pink feldspar grains give the beautiful stones their magnificent color. The red rocks contain many layers of a cross bedded red fusion of course to fine grained sedimentary rocks called the conglomerate fountain formation. In many places, the fountain formation lies directly upon Precambrian granite, aged at approximately 1.9 billion years old.

            An uplift of the current Rockies occurred some 72 to 45 million years ago, all the sedimentary red rocks here were pushed up at a near 40-degree angle seen at this angled tilt today. Sculpted by times’ patient chisel this ongoing carving is forever shaped by wind and waters power struck hammer blows checked by weathers erosive freeze and thaw.   The Fountain Formation, Morrison Formation and the Dakota Sandstone Formation rest more than two miles and 10,000 feet underneath the layers of Denver and yet sticks up here in the Foothills of Morrison.

If you look closely, you’ll see pebble- to fist-sized chunks of other rocks embedded in the amphitheater’s red rocks. Chunks this large can’t be transported far from a mountain range, so their very presence in the Fountain Formation, which predates the modern Rockies by hundreds of millions of years, indicates that they were shed off an older mountain range (Cook, 2015).

References

Cook Terri, (2015). Colorado By Nature: The Geological History Of Red Rocks. 5280.com, Sourced From: https://www.5280.com/2015/05/colorado-by-nature-the-geological-history-of-red-rocks/