The Colorado Plateau, the physiographic study area for this Program, is in reality a massive basin surrounded by highlands and filled with a myriad of plateaus. Covering an area of 130,000 square miles, it spreads over portions of southeastern Utah, northern Arizona, northwestern New Mexico and western Colorado. The underlying geology is ancient, at least 500 million years old. Drifting along as a portion of continental crust some 400 million years ago, the Colorado Plateau was covered by rising ocean waters. As the waters receded, deep layers of sediment in different thickness were revealed. Further sedimentary material worked its way down from surrounding high country, and the wind deposited dust and volcanic ash from active volcanoes from the west and southwest.

Under the weight of the accumulated material, the crust sank. Time, pressure and heat eventually solidified the deposits forming sedimentary and metamorphosed rock 2-3 miles thick. When the surrounding geologic material began to move, and uplifting formed the various mountain ranges on the continent, the sediment of the Colorado Plateau remained stable and in place. Because of the dense, thick nature of the consolidated sedimentary rock on the Plateau, volcanic activity in the region was unable to penetrate the surface. Instead, isolated ranges, such as the Henry, La Sal, Sleeping Ute, and Abajo mountains were the result of hot magma pushing up and penetrating these thick layers. When the volcanic activity tapered off and the magmas cooled and hardened, these mountains, termed "laccoliths," remained as a testament to the solid, ancient nature of the Colorado Plateau. Tectonic forces, while sculpting the Sierra Nevada and the Rocky Mountains, could only impress this area with shallow basins, low dome uplifts and long, continuous folds called "reefs." As the continent under and around us continues to move, the Colorado Plateau remains essentially motionless, slowly eroding and changing it's face with the passage of time.

The Plateau presents some interesting contradictions and puzzles. Although largely a desert environment of 130,000 square miles situated a mile above sea level, it also contains the Colorado River, one of the continent's largest rivers. Hard and soft rock battle for position in every canyon and on every mesa top. Side canyons of the larger rivers serpentine their way down and through the landscape as water and wind perpetually carve away at them. The sandstones of varied form, including Chinle, Navajo, Wingate, Entrada, Mesa Verde and countless others, are unique shapes and faces of rock. Alcoves, potholes, striations, bowls, basins, and deep canyons are all cut from these faces by the erosive actions of wind and water.

Within the sandstone layers are deposits of gypsum, potash and salt. Large seam deposits of coal, and fluid layers of oil and natural gas can be found in localized clusters throughout the region. Pockets of uranium and radium rich ores are folded into the layers. Red Halgaito shale, gray Mancos shale, gray limestone, and red and white Cedar Mesa sandstone confound the onlooker further. Throughout the area, you will likely be overwhelmed by the "hugeness" of it all.