Heat may explain why West is grand

The 130,000 square miles of deep river-cut canyons and exposed wind-scoured arches, the section of the earth that in Utah is called the Plateau Province, is as big a puzzle to geologists as it is awesome to any human interloper captured by the vistas of its environs.

Setting parts of the area aside as national parks — the Grand Canyon, Arches, Zions among them — is a testament to their unique grandeur. Determining how the entire Colorado Plateau came to be and has eroded into a geologic wonder of the world has been a tantalizing question for generations of scientists.

Three of them, one from Utah State University who was stunned as a boy by the stark, chlorophyll-deprived alter-ego of his green, rolling-hilled home in Wisconsin, have determined the best answer for the conundrum.

Every early explorer and the mappers who followed, including John Wesley Powell, have been obsessed with what on earth pushed all that land so high and how it has been shaped into stone monuments that, standing in one spot at dusk, can appear as squared off and imposing as city skyline or in another, as round and smooth as loaf of bread.

The most-accepted scientific theories to explain the nature of the place were partial at best, Joel Pederson, an associate professor in the USU Department of Geology said last week. Its particular history isn't quite crustal uplift along the Rocky Mountains, it's not just the result of erosion — even eons of it. Altered mantle could have made it rise up like a humongous bubble in the earth's landscape, but geologic buoyancy and rebound due to rock being unloaded at the surface was only a piece of the vast puzzle underground, he said.

"Not a single explanation by itself or in combination could account for how rock was hoisted and gradually eroded into the famous formations on top or could give a scientifically satisfying answer to the entire region," Pederson said.

Through a combination of applying the nature of nature and the known behavior of land masses and building it all into a mathematical model, Pederson et al., believe they have pegged the area's tectonic ancestry.

Pederson and his students made multiple, "exhaustive" trips to various parts of the region, calculating the total uplift and erosion of the plateau, mapping out the values using Geographic Information Systems to create a virtual model of the entire region, he said.

The teams were able to calculate total uplift and its distribution, "but we were missing parts that made up the total," he said.

A mathematical model presented in a paper published in the June 18 issue of Nature, by Pederson, Mousumi Roy of University of New Mexico and Thomas H. Jordan of University of Southern California, fills in the gaps. Heat in the lithosphere — the exterior surface of the landmasses — has permeated the region that straddles Utah, Colorado, New Mexico and Arizona. The result is the massive area of rock was pushed up about 6,000 feet above sea level, then cut away by forces above.

"This was the final piece that makes the others fit," Pederson said. "The sum adds up to the parts. That's exciting because it not only solves some geologic questions in this completely unique spot of the earth, we have the chance to provide something truly rare in scientific research — results that are more answers than questions. Scientific research almost always goes the other way."

E-MAIL: jthalman@desnews.com