Originally Posted by
Tourist in MSN
Your photos clearly look like they are man made, and I expect you are correct. But if you find any that have more sand and gravel with smaller cobbles, they could be eskers, a natural post glacial feature.
https://en.wikipedia.org/wiki/Esker
Smaller eskers are likely hard to find, as they are subject to erosion but you might spot a few if you were looking for similar hunting features.
And sometimes they were mined for aggregate.
The ones on Rollins Pass have been studied extensively. They aren’t glacial. The ones that I’ve found on the Colorado plains aren’t anywhere near any glaciation features. We had extensive mountain valley glaciers but the glaciation didn’t reach out of the Colorado mountains. Glaciers here didn’t come down much below 8000 feet and were somewhat localized. Even the top of Rollins Pass wasn’t glaciated.