Rocky Mountains version 2.0
There’s a fun website that lets you input your address and then run the way-back machine to see your land through Earth’s timeline. Typing in Bailey, Colorado, then jumping back 15-50 MILLION years at a time, you can watch tectonic plates shift, mountain ranges form and erode, and seas fill and recede. The land is in motion, very, very slow motion, but notable motion nonetheless. In James Michener’s, Centennial, a novel about Colorado, he begins - as he does with most of his gargantuan novels - starting with very ancient history:
"WHEN THE EARTH WAS ALREADY ANCIENT, of an age incomprehensible to man,.."
Michener, James A.. Centennial (p. 31). Random House Publishing Group. Kindle Edition.
This ancient history, of which I have leaned heavily upon Michener’s telling, rolls back the eons to see what we now know held a Rocky Mountains version 1.0, better known as the Ancestral Rockies. Pressure from the Earth’s mantle, the inner layer, began to move and break up basement rock roughly 300 million years ago. Enormous pressure gave way skyward, pushing up through the seabed to elevations many thousands of feet above the sea level. This land rise was likely not as sharply peaked as our mountain ranges are today, but they dominated this area. This uplift gained height for 10 million years or so and then stopped.
Erosion was ongoing during this uplift time, with streams becoming rivers the higher it went up and gravity pulled down. As it slowed and stopped, the peaks continually wore down by erosion with water flow, wind, freezing, and thawing. Over the next 40 million years, the high peaks returned to flat land. To put this into the ‘incomprehensible to man’ time, that means that 250 feet of mountain eroded every million years or 3 inches per thousand years. To perceive this within a human lifetime, would mean micro millimeters or rather, just imperceptible.
250 million years ago, what we would call the continents of the Americas and Africa, were pushing toward each other. This compression would bring the Appalachian Mountains, the older cousins to the Rockies, into being, their grand peaks now eroded to rolling hills.
Next came water, or rather, again came water. Clay and silt laid down in varying layers, compressing their sediments. The sediment layers began to include the early creatures we now find in the fossil record. A visit to Dinosaur Ridge in Morrison shows what was once a shoreline that the dinosaurs wandered through, on wet sand, their footprints leaving behind a record for our modern day, lifted upright like a picture hung for all to see. To get that picture to hang upright, tectonic plates, as they always had been, were on the move.
Out west, our current lands were under deep seas as of 70 million years ago and the land began to churn again. A cocktail of water and sediment weight, weak basin land areas, and volcanic activity began moving rock upward again. Some of the rocks from the Ancestral Rockies rode up to exposure again to tell their old stories to the geologists. Take a look at the rock cuts along Hwy 285 between Morrison and Grant, and note the folded, multi-colored layers of sediment, billion-year-old pink granite, purple and green shale, red sandstone, and various shades of quartz, once buried deep and now exposed.
The Rockies pushed upward and sent the sea to the edges at Morrison. Rivers formed and gained momentum the steeper the peaks rose. A sediment of sand and silt from the peaks was carried by the rivers down to the plains. Then, volcanos became very active 40 million years ago, and for the next 15 million years, ash and rock rained down on the land. 23 known volcanos, some larger than Vesuvius, created a turbulent epoch choked with toxic gases. Uplift kept rising and the landmass grew, piling up thousands of feet deep.
The volcanos exhausted themselves over time and activity began moving again underground. The entire western North America land mass began to rise to near the elevations we are at today. Waters receded to lower areas and major rivers began to follow nearly the paths we know today.
One million years ago, just yesterday in the span of time we’ve covered, the Ice Age began. The reach of the glaciers spread to the Foothills in thin fingers of ice. Smaller, high-elevation glaciers carved many of the peaks we know today. 10,000 years ago, the ice finally receded. The fault lines remain and are active, in geologic time, which is relatively quiet in our lifetimes. The soup of geologic activity left deposits of prized minerals that will shape human history to come. The massive upheavals have quieted for now allowing for the elements of life to come into play. Trees, grasses, mosses, lichen, wetland plants, flowers, and all that walks, chomps, buzzes, hunts, and scampers over the ground found it good.
This grand fly-over of time is my own piecing together of some basic research. I have purposely steered clear of naming geologic eras and formations as this is a prime area I would likely make many errors, I am in awe of what geologists have been able to puzzle out in the rock record. I would love to be corrected by the true geologists out there. Please chime in where I have veered off course.
Sources:
• https://dinosaurpictures.org/ancient-earth#0
• Michener, James A.. Centennial , Random House Publishing Group. Kindle Edition.
• Williams, Felicie; Chronic, Halka. Roadside Geology of Colorado. Mountain Press Publishing Company. Kindle Edition.
• https://coloradogeologicalsurvey.org/geology/colorado/
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