Sage Grouse Saga

Greater sage grouse, the largest grouse in North America, inhabit sage grasslands of the Intermountain West, from Colorado to the Columbia Plateau and from southern Alberta to southern Utah. Closely tied to their habitat, these grouse feed solely on the sage plant in the winter while supplementing that diet with a variety of forbs, insects and grasses during the warmer months. Unlike many game birds, they do not possess a muscular crop and cannot digest hard seeds.

Come spring, sage grouse gather in clearings (known as leks) at dawn and dusk, where the dominant males attract mates with ritualized strutting, tail fanning and a variety of noises from their air sacs; most of the females mate with only one or two of the performers. Nests are placed on the ground and females are solely responsible for both incubation and protection of the young; six to twelve eggs are generally produced. Able to forage soon after birth, the young are vulnerable to a wide range of predators, including snakes, prairie falcons, crows, magpies, badgers, coyotes, bobcats and owls.

Once abundant across the American West, greater sage grouse have long been threatened by habitat loss; their population, estimated to have been about 16 million in the early 1900s, has fallen to less than 500,000 today, a drop of 97% over the past century. The loss of sage grasslands to mining, ranching and oil production has been primarily responsible for this decline and efforts to list the greater sage grouse as an Endangered Species have been successfully blocked by Western Governors and their Federal colleagues. Perhaps a 99% population decline will be more convincing.

The Elusive Ringtail

The ringtail, named for its bushy, banded tail, is a small, nocturnal omnivore of the western U.S. and northern Mexico. Extremely agile, these cousins of the raccoon favor semi-arid areas with rock outcrops and open woodlands; there they hunt small mammals, birds and lizards and seasonally feast on nuts and berries. Since they are active primarily at night, ringtails are seldom encountered by hikers and campers.

Though often called ringtail cats, due to their size and behavior, they are not felines; once domesticated by miners to control rodents, they are also known as miner cats. Ringtails are solitary for most of the year but pair off in late winter or early spring to mate; the litter of kits (usually 2-4) are born in late spring and stay with their mother through summer. Dens are usually placed in small caves or rock crevices but ringtails are superb climbers and often rest in trees.

Natural predators of ringtails include hawks, owls, coyotes, fox and bobcats. Those fortunate enough to escape these hunters often live 7-8 years in the wild and have been known to live 15 years or more in captivity.

The Virgin River Staircase

The North and East Forks of the Virgin River rise on the south face of the Markagunt Plateau, in southwest Utah, amidst colorful outcrops of the Claron Formation. From these early Tertiary sediments, the tributaries begin to flow back in time, entering Zion National Park through Cretaceous Dakota Sandstone before carving magnificent canyons of Jurassic Navajo Sandstone; the North Fork has produced the more famous Zion Canyon while the East Fork sculpted Parunaweep Canyon.

The Forks join west of Zion, where the Virgin River begins a journey across Triassic redbeds, interrupted by Quaternary basalt flows along the Hurricane Fault. Beyond St. George, the river dips into the northwest corner of Arizona, where it has carved the spectacular Virgin River Gorge through Permian limestone and older, metamorphosed Paleozoic strata. West of the Grand Wash Fault, which marks the west edge of the Colorado Plateau, the canyon widens and the river enters the stark landscape of the Mojave Desert. After flowing into Nevada, the Virgin River curves to the south and joins the Colorado River within Lake Mead.

Western rivers are appealing to the naturalist in many ways. Producing ribbons of vegetation through arid landscapes, they also reveal the complex geology that underlies and explains the rugged, surface topography. Though relatively short, the Virgin River of Utah-Arizona-Nevada has bestowed its gifts in spectacular fashion.

Unaweep Canyon Mystery

While the field of plate tectonics has solved many geologic mysteries, others remain. One of these is Unaweep Canyon in the northern portion of the Uncompahgre Plateau, in western Colorado; unlike other canyons, it has two mouths and a divide along its course, which is now traversed by Colorado Route 141.

Geologists have long debated the natural history of Unaweep Canyon. Some have suggested that, since the canyon is U-shaped, it was carved by mountain glaciers during the Pleistocene; however, closer examination of its floor has revealed that it is a V-shaped, stream-cut canyon, since filled with erosional debris to produce the flattened bed. Others, realizing that the small streams that now flow east and west from the divide could have not produced this magnificent canyon, with its massive walls of hard, Precambrian rock, theorized that the Colorado River originally sculpted Unaweep before changing course to skirt the northern edge of the Plateau.

The most recent evidence suggests that the Gunnison River, which also carved the Black Canyon, once cut through the Uncompahgre Plateau, joining the Dolores River on its west side before flowing northwestward into the Colorado. Based on examination of gravels and other sediments, it appears that the Gunnison gradually sliced through the Uncompahgre ridge as it rose with the rest of the Colorado Plateau during the Miocene-Pliocene Uplift, 25-10 million years ago. A landslide is thought to have disrupted the Gunnison's flow within the Canyon (presumably about 6 million years ago), causing it to back up and eventually flow northward to join the Colorado in the Grand Valley. The abandoned Canyon is now drained by East and West Creeks, too weak to remove the erosional debris of the powerful Gunnison. Time and more field work will tell if this is the true solution to the Unaweep Canyon mystery.

Jurassic Parks

The Colorado Plateau of the Western U.S. harbors one of the most extensive exposures of Jurassic strata on our planet. Stretching from 200 to 135 million years ago, the Jurassic Period covered the heart of the Mesozoic Era, the Age of Dinosaurs.

A number of our National Parks and Monuments are famous for their Jurassic deposits and, by extension, their cargo of dinosaur fossils. Dinosaur National Monument, in northwest Colorado and northeast Utah, is a showcase for the Morrison Formation; deposited in a long, shallow basin, from Canada to New Mexico, this layer cake of mudstones, siltstones, coal and sandstone is famous for its late Jurassic fossils. A bit older, the Entrada Sandstone, deposited in the mid Jurassic, is highlighted at Arches National Park, in eastern Utah, where it has been sculpted into a spectacular array of fins, natural bridges and arch formations.

Perhaps most famous of the Jurassic sedimentary rocks is the Navajo Sandstone, deposited about 190 million years ago when a vast desert covered the region. Relatively soft and heavily jointed, this sandstone forms the upper cliffs of Canyonlands National Park, the scenic domes of Capitol Reef National Park and the towering walls of Glen Canyon, now drowned by Lake Powell. Separated from the Navajo Sandstone by the Kayenta Formation, the Wingate Sandstone yields the middle cliffs of Canyonlands and the majestic, sheer walls of Colorado National Monument; though officially dated from the onset of the Jurassic, some geologists argue that, based on its fossil contents, the Wingate was deposited near the end of the Triassic.

Claron Lake

When the Rocky Mountain chain began to rise, some 70 million years ago, the crust to its west was stretched, producing a mosaic of ridges and broad basins. Drainage into the basins created large inland lakes, including the Green River Lakes of the Utah-Colorado-Wyoming Tristate and Claron Lake of southwest Utah. All of these lakes gradually filled with sediments of the Paleocene and Eocene Periods (60-50 million years ago); the deposits in the Green River Lakes would eventually yield the famous oil-shales of the Roan Plateau while deposits in Claron Lake would become prized more for their natural beauty.

Compacting into layers of limestone, dolomite, siltstone and conglomerates and capped by volcanic tuff from the Oligocene Period (30 million years ago), the Claron Formation was lifted with the rest of the Colorado Plateau during the Miocene-Pliocene Uplift, some 25-10 million years ago. Erosion and faulting would eventually expose the Claron beds along the edge of regional plateaus; Cedar Breaks National Monument, a spectacular natural amphitheater on the west edge of the Markagunt Plateau and Bryce Canyon National Park, on the east edge of the Paunsaugunt Plateau, protect the most scenic exposures.

Rich in iron oxides and manganese oxides, the colorful limestones and dolomites have eroded into striking rock formations, known as hoodoos. These pinnacles, capped by more resistant rock layers have been split apart by stream erosion and freeze-thaw fracturing. Once lying beneath an ancient lake, they now gleam in the bright Utah sun and adorn calendars across the globe.