How did the Green River flow "uphill" for about 100 miles?

[Glenn MacGrady]

Many canoeists have paddled the Green River, which is the Colorado's largest tributary. We have trip reports of the Green on this site. But did you know there is:

". . . an American mystery which has baffled geologists for a century and a half: How did a river carve a path through a mountain in one of the country's most iconic landscapes? Scientists have long sought an answer to this question of how the Green River, the largest tributary of the Colorado River, managed to create a 700-meter-deep canyon through Utah's 4km-high Uinta Mountains instead of simply flowing around them. The question is particularly confounding because, while the Uinta Mountains are 50 million years old, the Green River has been following this route for less than 8 million years."

New research suggests this can be explained by ""lithospheric dripping" of the Uinta Mountains. I don't quite understand this, but it seems to posit that entire mountain ranges can bounce down and then back up.

https://phys.org/news/2026-01-geologists-mystery-green-river-uphill.html

Then, of course, there's the theory that the entire Colorado River once flowed in the other direction.

Ancient Colorado River Flowed Backwards

An ancient river roughly the size of today's Colorado River once flowed from California's Mojave Desert northeast through Arizona and Utah, in the opposite direction of the modern Colorado River, a new study finds.

www.nbcnews.com

Wouldn't it be simpler if rivers and mountains (and lakes, of course) would stay in their "natural" state?

 

[Alan Gage]

I've been getting into geology over the last few months and have heard some about this. I don't think there remains much question of how it carved a path through the mountains rather than going around them. Multiple very high mountain ranges were created in that area and after millions of years of erosion the valleys had filled in and buried what remained of the mountains, leaving an essentially flat landscape. More millions of years later the area began to be uplifted and what were broad and slow moving rivers with little elevation change began to flow faster and stronger. As the landscape continued to be uplifted the rivers continued removing more and more of the accumulated debris as they dug deeper channels. Eventually they reached the buried mountains and began to cut vertically down through them. Over more millions of years we ended up with what we have now: The buried mountains have been mostly excavated and now rivers run straight through them.

When mountain ranges are created they are obviously very heavy and they can cause the mantle to slump and the area can lose elevation. As they become more and more eroded the mantle can begin to rise back to "normal" levels and cause the area to uplift. Other forces can cause uplift as well. I believe this is also happening in the Canadian shield. The land had dropped under the weight of the glaciers and it's still rebounding after the glacier melt.

TLDR: The rivers didn't punch through the mountains, they wore through from the top down at a time when the mountains already existed but were buried in debris.

Alan

 

[Steve in Idaho]

Fascinating.
Flaming Gorge and the Uintas are awesome.

From the second article...

The modern Colorado River's headwaters are in the Rocky Mountains, flowing southeast to the river's mouth in the Gulf of California.

Oops.