The state was submerged under a warm shallow sea. At least part of Colorado was covered by shallow water during the Middle Ordovician. At the time, Colorado was home to invertebrates like articulated brachiopods, conodonts, gastropods, ostracods, pelecypods, sponges, trilobites, and worms (known from trace fossils).
Paleontology in Colorado - Wikipedia
https://en.wikipedia.org/wiki/Paleontology_in_Colorado
There was a huge lake, first in the Canadian arctic. It was the remnants of a ice sheet that was melted by an impact of a asteroid or comet. That sheet was vaporized at the site and melted for hundreds of miles. That water flowed down into the basin that makes up the plains of the US.
Further down the line, that water ran off to the Gulf of California down what is today the Colorado river basin and the Grand Canyon area. You can see the water marks carved into the entire Western part of the continent.
Some of those things took thousands of years. Others were carved in a few years.
Life on earth has not always been the pleasant, idyllic, scene that we are all used to today.
Something the size of a football field hits us...and its lights out for everyone but the roaches.
I was just about to remark that I’m on a 2000 foot mountain and I can go out in the back yard and kick up sea lily and various seashell fossils with no effort.
I’m pretty certain they didn’t all just walk here.
Funny. I was just thinking about the valleys of California in the same vein...
