Utah –
Geologists have pinpointed a surprising explanation for the winding course of the Green River in Utah, which appears to flow *through* mountains rather than around them. This long-standing scientific puzzle, dating back over a century, now has a compelling geological basis.
The river carves through the Uinta Mountains, forming Lodore Canyon, which reaches depths of approximately 700 meters. This is unusual, as water typically flows around mountainous terrain, not directly through it.
The Green River, a major tributary of the Colorado River, travels hundreds of kilometers through Wyoming and Utah before converging at Canyonlands National Park. A map view reveals a course that seems to ascend *over* the mountains, but scientists emphasize that the river isn’t defying gravity. Instead, the phenomenon is linked to large-scale geological shifts over time.
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Novel research published in the Journal of Geophysical Research: Earth Surface suggests the key lies in a process called lithospheric drip. This occurs when dense material deep within the Earth’s crust slowly sinks into the mantle, pulling down the surface above it before rebounding. Understanding these geological forces is crucial for interpreting Earth’s landscape.
According to Dr. Adam Smith, lead researcher from the School of Geographical & Earth Sciences, University of Glasgow, this process explains how the Green River was able to cut through the southern Uinta Mountains. “For around 150 years now, geologists have debated how the river became integrated, which is a challenging question in a tectonically quiet area. We think we’ve gathered enough evidence to show that lithospheric drip pulled the land down enough to allow the river to connect and integrate,” Smith said.
An Unusual Formation
Using seismic reconstruction and data modeling, the research team identified a circular, cold anomaly approximately 200 kilometers beneath the Uinta Mountains. This anomaly is believed to be the remnant of the dense material that “dripped” down into the mantle.
As this process unfolded millions of years ago, the land above subsided, creating a lower pathway for the river’s flow. Researchers estimate this occurred between 2 and 5 million years ago, coinciding with the period when the Green River likely began carving its path through the mountains and connecting with the Colorado River. This discovery highlights the dynamic nature of Earth’s crust and its influence on river systems.
The findings demonstrate that the river’s seemingly uphill course is a result of the mountains sinking, rather than water flowing upwards. The research also refutes earlier hypotheses suggesting the river existed before the mountains or was formed by sediment buildup causing it to spill over the peaks.
Geological evidence and the new models strongly support the lithospheric drip mechanism as the primary cause of this unusual river course. This breakthrough resolves a longstanding mystery in North American geomorphology and demonstrates how deep Earth processes can dramatically reshape surface landscapes, including the courses of major rivers.
(rns/rns)
