Unraveling the Geological Mystery of the Green River in Utah
For over a century, the path of the Green River as it winds through the Uinta Mountains in Utah’s northeast has baffled geologists, seemingly defying the laws of physics.
Typically, rivers follow the natural contours of the land, carving out their course over millions of years. However, the Green River, which has been flowing for a mere 8 million years, cuts across the 50-million-year-old mountains to meet the Colorado River, creating the 700-meter deep Canyon of Lodor that runs perpendicular to the range.
Geologist Adam Smith from the University of Glasgow led a team to investigate this enigma. Their findings revealed that the Green River did not have to flow uphill at all. Instead, the mountain range experienced a phenomenon known as lithospheric drip, where the dense mineral chunk at the base of the lithosphere dripped into Earth’s mantle, temporarily lowering the mountains.
Smith and his team noted that other rivers in the Uinta Mountains provided evidence of recent changes in mountain height, supporting their theory of lithospheric drip. The mountains rebounded by 400 meters, forming the canyon we see today.
Seismic imaging revealed a cold, round chunk about 200 kilometers below the surface, indicating the presence of the drip. The thin crust below the mountains further supported the idea that lower layers had been torn away by the drip.
Once the drip detached from the lithosphere 2-5 million years ago, the mountains rebounded, solidifying the Green River’s course. The merger of the Green and Colorado Rivers millions of years ago reshaped the continental divide of North America, influencing habitat boundaries for wildlife.
This groundbreaking research is published in the Journal of Geophysical Research: Earth Surface.
