Utah
At the northern end of Zion Canyon, the Virgin River has etched a deeply incised route known as the Narrows.
Ayawning, magnificent tangle of soaring cliffs and sheer canyons on the edge of the Colorado Plateau, Zion National Park is one of the most renowned steps on the Grand Staircase. Zion sits midway down the staircase, in a canyon carved by the Virgin River. The setting is so picturesque, it was named for the Mormon connotation of heaven on earth.
The Colorado Plateau is a massive region, covering much of the Four Corners sector of Utah, Colorado, New Mexico, and Arizona—an area that has been uplifted, tilted, and eroded into a jungle of high desert canyons not found anywhere else on Earth. This region was once an inland sea, where sediments settled over many millions of years, in some places 10,000 feet thick. When the sea dried up, the desert moved in, and an ocean of shifting sand dunes took its place. After being lithified into sandstone by time, heat, and pressure, these layers now represent 150 million years of mostly Mesozoic-aged rock, divided into multiple formations, each with its own distinctive colors, textures, and erosive patterns.
Zion Canyon was carved out very rapidly by the Virgin River, leaving many side canyons hanging high above the main canyon.
At one time, all these layers were flat and hidden deep in the crust. But starting around 20 million years ago, during one of several episodes of regional uplift, the entire Colorado Plateau raised as high as 10,000 feet. This extreme change in elevation steepened the angle of the streams draining the region, boosting their erosive power as they ran over the landscape. One of the rivers that became exponentially more powerful was the Virgin River, the north fork of which cuts through Zion Canyon as it flows off the edge of the Colorado Plateau.
The view from Angel’s Landing, one of Zion National Park’s most well-known formations, looks right down the gut of Zion Canyon.
Petrified sand dunes with cross-bedded layers can be found east of Zion Canyon. These inclined layers at irregular angles to each other are caused by changing water or wind currents as the strata are laid down.
The first pulse of this period of heightened erosion erased all the more recent rock from Zion, scraping away more than 6000 feet of stone and sediment from the last 60 million years of deposition from the Cenozoic Era. Late Cretaceous Dakota Sandstone was left as the youngest exposed layer in Zion. The erosive force of the Virgin River became even more powerful in the last million years, when over half the down-cutting of the canyon took place. In that time, the canyon has deepened by more than 1300 feet, creating the upper canyon that is the heart of the national park. This high rate of carving continues today—in excess of 3 million tons of rock and sediment are carried downstream toward the Colorado River each year.
The Virgin River eroded its main channel much faster than the waterways that empty into it eroded their channels, leaving side canyons hanging high above the Virgin River Valley. These tributaries often end in waterfalls plunging from dizzying heights above the main canyon—cascading spectacles such as Emerald Falls and Mystery Falls, which help make Zion one of the world’s most scenic places.
You might fly over Zion en route to Saint George, Utah, or Las Vegas, Nevada. Look for a deeply incised canyon on the edge of the raised Colorado Plateau.
