Nature Discovery with Renée: rocks, part two

Time for an adventure this week with Librarian Renée! This week’s Nature Discovery is part two  featuring geology; we are going back to the future!

In last week’s blog we got the dirt on rocks – what they are made of and how they are made. This week we are going to hop in our time machine to see how the events of the past shaped our landscape we see today. So buckle your seat belts, we are starting at the beginning and going back to the future!

We are setting our time machine to 4.6 billion years ago, when the earth is being formed. The earth is very hot and unstable as land and water are beginning to form on our home. It’s an exciting time, but not very hospitable. Let’s move ahead to 3.5 billion years ago, where we will see the first signs of life! During the preCambrian period, the most simple, single cell organisms, called prokaryotes emerged. Bacteria is a prokaryote.


We have a lot of time to cover before our next big event. We are going to jump ahead to 570 million years ago to reach the Cambrian time period. From our time machine we can see land formations and large areas of water. Look closer and you will now see the first invertebrates swimming in the oceans. If we blast almost 100 million years ahead to the Ordovician time period, we can now see the first vertebrates, fish! 

Fossil invertebrates from the Cambrian time period

We have to travel 60 million years to reach our next time period, the Devonian time period. As you gaze out your window you will see the very first land animals–amphibians–move ashore. As we watch these animals crawl on their newly formed four legs we also see the first forests emerge, consisting of ferns that grow like trees. As we travel through this time period, we see everything becomes lush and green. Our planet is full of carbon-producing life! This is when we enter our next time period, Carboniferous, at roughly 360 million years. This time period is when coal will be deposited, a byproduct of all that carbon. This is also when mountains will be built. Buckle up because we are going to zoom 60 million years ahead to watch something truly spectacular: the birth of our Ancestral Rocky Mountains. No, these are not the purple mountain majesties of today, but rather the forebears of our future Flatirons. But I’m getting ahead of myself, there is still a lot to happen!

Let’s jump ahead 50 million years, to the Permian time period where we will see further branching and variations of life forms. Add another 50 million and we enter the Triassic period. During this time period we see a great extinction of many life forms, yet others will emerge in their place, such as dinosaurs and the earliest relatives of mammals. Pushing ahead another 50 million years and we enter the Jurassic period and dinosaurs rule the lands, but the earth is plentiful with early mammals and birds as well. 

Wildlife isn’t the only thing we see change on our many stops. Our Ancestral Rockies are being beaten with wind, rain, snow, and ice, causing the mountains to slowly erode. Each boulder, chunk, chip, and grain become deposited layer, by layer, by layer. As we watch we can see early reptiles walk across one layer and dinosaurs walk across another. As the mountains erode, the layers get bigger and bigger. Eventually the Ancestral Rocky Mountains, along with the dinosaurs, are no more and we enter the Cretaceous period. Our time machine reads 145 million years ago.

If we were to venture out of our time machine at this point in our history, we would need a boat! As we can see, Colorado is now underwater! With the mountains gone, a shallow seaway formed that connected our modern day Arctic Ocean and the Gulf of Mexico.

Back in our time machine, we are moving ahead to 80 million years ago. Can you hear that? It’s a rumbling noise and it’s getting louder! Everything is shaking!! What’s happening?? We are again witnessing a historical moment. Once again we are entering a mountain-building stage. There is much activity happening on the earth’s crust! Movement causes a ripple, much like a wave.  Another movement causes one plate of crust to go under–or subductanother. We are watching the birth of our current Rocky Mountains! Keep watching, because something truly unique and fascinating is about to happen.

As the Rocky Mountains, made of metamorphic rock in the core of the earth, begin to peek through, they puncture the layers of over 150 million years of sediment, deposited by our previous ancestral rockies. The shallow seaway cemented these layers together forming sedimentary rock.  As the mountains grow, they bring the recycled rock formations with them. Slowly, slowly, slowly, until…..

At 65 millions years we see our beautiful Flatirons standing upright! 

Over the next 65 million years we will see the Paleogene period, the seaway has receded and mammals begin to diversify and take their place in the new world. Flowering plants will begin to take over much of what was occupied by ferns. It is beginning to look like home. After 43 million years we see our next time period, the Neogene. If we look closely we may be able to see the very first hominins, our ancestors. Hope you brought a coat because we will also witness the growing and thickening of the ice caps leading to the ice age. Moving forward to 2.5 millions years ago, we make it to our last and current time period, the Quaternary time period. We don’t see much geologic change, but we do see the glaciers receding to the poles. We see the extinction of mammoths and the saber- toothed cats.  2.5 million years go by in a blink and we are back to the future.

What an adventure!  How wonderful it would be to actually travel through time. Actually you can! Hike along the foothills and you can see rocks that were once beach side property and the waves are still visible. Take a walk on the very rock that dinosaurs roamed over and in some places you can still see their footprints. Every time you take a hike, you are taking a trip through time. Enjoy the journey!

For further reading, check out The geology of Boulder County, by a fellow naturalist Raymond Bridge. There are many more stories that rocks have to tell!

Until next time, Happy Adventures! -Renée

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