Why 'Mile-High City' Is So High Up
It has to do with water from millions of years ago
By Neal Colgrass,  Newser Staff
Posted Mar 16, 2015 7:20 PM CDT
A marker carved in one of the west steps of the State Capitol denotes the "one mile above sea level" elevation in Denver on Friday, March 13, 2015.   (AP Photo/David Zalubowski)

(Newser) – What makes the High Plains so darned high? Well, geologists say, maybe the Earth just got lighter and floated up like a plank of wood for millions of years. In the journal Geology, experts say water beneath the Western US may have infiltrated an area of the continental plate and made it light enough to rise some 6,000 feet, the AP reports. It started millions of years ago when the West was mostly at sea level. The Farallon oceanic plate had slid under North America and, the theory goes, reacted to pressure from above and heat from below by releasing water. That water rose up into densely packed minerals, turning them into minerals so light that the Earth's crust slowly "floated" and became the High Plains. But it's still just a theory, says co-author Craig Jones.

"Do we think this is 'the' answer? No," says Jones, a geology professor at the University of Colorado Boulder. Yet the mystery is an awkward one for Colorado geologists: "We probably need to figure this one out, guys, because it's kind of embarrassing," Jones once said in a TV interview. The problem is that no deformations like volcanic activity or major faults are there to explain the High Plains, he tells Science Daily. "What we suggest is that by hydrating the lower crust, it became more buoyant, and the whole thing came up," he says. "It's like flooding Colorado from below." Seismic studies support the theory, too, saying the Earth's crust is lighter and more hydrated at higher elevations. (Now, did a "golden spike" in the geologic record kickstart the "Age of Man" in 1610?)