Sum of its Parts: USU Geologist Helps Solve Colorado Plateau Puzzle
Thursday, Jun. 18, 2009
USU alum Scott Cragun MS'07, a former student of Joel Pederson, conducts a field survey in southern Utah near Glen Canyon. Photo by Rob Mackley MS’05.
Pederson, associate professor of geology, published research findings about the Colorado Plateau in the June 18 issue of 'Nature.'
When taking in the spectacular vistas of Grand Canyon, Arches, Zion and other national parks of the Colorado Plateau, visitors often wonder how the landforms got so high and so deep. For more than a century, geologists have wrestled with these two main conundrums about the 130,000-square mile plateau: how it was uplifted and how it eroded. Utah State University geologist Joel Pederson and colleagues from the University of New Mexico and the University of Southern California believe they’ve solved the first of these puzzles using, along with a string of clues, a rigorous mathematical model.
In a paper published in the June 18 issue of Nature, Pederson, Mousumi Roy of UNM and Thomas H. Jordan of USC, explain the patchwork of sources that caused the massive plateau province, which straddles the states of Utah, Colorado, New Mexico and Arizona, to rise from sea level to a mean elevation of 6,000 feet. Their research was funded by the National Science Foundation.
“This is an exciting discovery because much of the science of geology has grown out of our knowledge of the Colorado Plateau,” says Pederson, associate professor in USU’s Department of Geology. “Our findings solve a mystery that will help us unravel even more information about this geologically critical region.”
During the past few decades, geologists have identified four possible sources of the plateau’s uplift: crustal uplift along the Rocky Mountains, dynamic support from the Earth’s mantle, rebound due to the unloading of rock by all the erosion and buoyancy due to an altered mantle under the plateau. But scientists couldn’t agree if one, some or all were responsible for the area’s ascension. Nor could they determine, if more than one source hoisted the rock that gradually eroded into the region’s iconic buttes, canyons and arches, how much of each source contributed to the entire plateau.
Using computer software in previous research, Pederson worked with students to measure and calculate the total uplift and erosion of the plateau.
“We exhaustively mapped out these values using GIS and made a virtual model of the entire region,” he says. “We were able to calculate total uplift and its distribution, but we were still missing information about the parts that made up this total.”
The amount of uplift from alteration of the mantle and heat conduction, the last of the four sources to be calculated, is explained in the current research with a mathematical model developed by author Roy.
“Roy’s model shows how heating of the lithosphere has gradually permeated the region over 30-40 million years, causing a widespread area of rock to become buoyant and result in more than a kilometer of uplift,” Pederson says. “This is exciting because this mathematical model solves the final piece of the uplift equation adding up to the sum of the parts.”