Green River 'uphill' illusion may be caused by movement of the land

A new study led by Adam Smith at the University of Glasgow reports that the Green River did not reverse direction; instead, the Uinta Mountains’ deep lithospheric root became unusually dense, sank into the mantle, and later detached about two to five million years ago, leaving the river’s course appearing to slope uphill.

The Green River in Utah looks as if it flows uphill through the Uinta Mountains, a puzzle noted by scientists for more than a century. A recent study published in the Journal of Geophysical Research offers an explanation rooted in deep Earth processes. Geologists led by Adam Smith of the University of Glasgow report that the river did not reverse direction; rather, the land beneath it moved over millions of years. The work links changes in the mountain's deep lithospheric root to the river's apparent slope. Key findings: - The river’s apparent uphill flow is described as an optical effect caused by movement of the land, not a reversal of the river’s direction. - The Uinta Mountains developed an unusually dense lithospheric root that slowly sank into the mantle and pulled the surface lower over millions of years. - That dense root is reported to have detached around two to five million years ago, after which the mountains began to rise again while the river kept its established course. - The study was led by Adam Smith of the University of Glasgow and published in the Journal of Geophysical Research. Summary: The study reframes the long-standing observation as a consequence of deep lithospheric changes rather than a change in the river’s flow. It highlights how slow, subsurface processes can alter surface drainage patterns. Undetermined at this time.