Why Is Denver a Mile High

Geological Society of America ^ | 3/5/2015 | Staff

[JimSEA]

University of Colorado Boulder researchers propose a novel mechanism to explain the region’s high elevation No one really knows how the High Plains got so high. About 70 million years ago, eastern Colorado, southeastern Wyoming, western Kansas, and western Nebraska were near sea level. Since then, the region rose about 2 kilometers, leading to some head scratching at geology conferences.

Now researchers at the Cooperative Institute for Research in Environmental Sciences (CIRES) and the Department of Geological Sciences at the University of Colorado Boulder have proposed a new way to explain the uplift: water trapped deep below Earth’s crust may have flooded the lower crust, creating buoyancy and lift. The research appears online this week in the journal Geology and could represent a new mechanism for elevating broad regions of continental crust.

“The High Plains are perplexing because there is no deformation—such as major faults or volcanic activity—in the area to explain how this big, vast area got elevated,” said lead author Craig Jones, a CIRES Fellow and associate professor of geology at CU-Boulder. “What we suggest is that by hydrating the lower crust, it became more buoyant, and the whole thing came up.”

“It’s like flooding Colorado from below,” Jones said.

Jones and his colleagues propose the water came from the subducting Farallon oceanic plate under the Pacific Ocean 75 to 45 million years ago. This slab slid underneath the North American continental plate, bringing with it a tremendous amount of water bound in minerals. Trapped and under great pressure and heat, the water was released from the oceanic plate and moved up through the mantle and toward the lower crust. There, it hydrated lower crust minerals, converting dense ones, like garnet, into lighter ones, such as mica and amphibole.

[JimSEA]

Limestone and mudstone formed on the Indian and Eurasian plate margins now are found in the peaks of the Himalayas as a result of the collision between the two plates. Plate tectonics solves many problems posed by structural geology. The only requirement for soils to become rock is pressure and heat. Any soil that is buried deeply enough will become rock. Most of the biological material will leach out or, in rare instances, fossilize.

It’s a little bit arrogant to attempt to read my mind. Nothing I’ve said is in conflict.

[cotton]

Indeed. Walt Brown is one of my favorite scientists.

[editor-surveyor]

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Keep pumping up smoke!

The conflicts are there, and won’t go away.