At the end of her latest jaunt to southeastern Utah, Meladye Shively was ready to head back to Denver in her well-traveled (245,000 miles and counting) white Nissan pickup. Having explored Canyonlands' Island in the Sky for the first time, she'd decided to drop off the peninsular mesa toward the Colorado River gorge via the Shafer Trail.

"I'd never even heard of it before," she admitted during a break at a river viewpoint, "but I didn't want to go home the boring way."The precipitous, unpaved Shafer Trail is anything but boring.

As seen from Dead Horse Point State Park nearby, the Colorado and its tributaries have carved an awesome landscape reminiscent of territory a little farther south along the same great drainage - the Grand Canyon.

A major difference, however, is that here a few roads link the plateau above with the river below. The handiest among these is the Shafer - a gully-crossing, side-winding route that is, at times, a cliffhanger.

Literally.

In the 1880s, Frank and J.H. Shafer began improving the trail - once used by Indians and 19th century outlaws - to move cattle to and from summer rangelands. At the head of a canyon they would work the cows up a steep but traversable slope.

"There were spots on it that were maybe 3 feet wide," said John Simmons, an interpretive ranger at Canyonlands National Park. "Ranchers tell stories that if cattle got scared and backed up on the switchback," they could lose a few of the animals when they tumbled over the edge.

Uranium prospectors and oil companies widened the route in the 1950s, during the Moab area's mining boom years. Much of it was included within Canyonlands' northeastern boundaries when the park was established in 1964. "We do grade it periodically" today, Simmons said.

The Potash Road and the Shafer Trail - unpaved for 18 miles between the Moab Salt Co.'s evaporative ponds and Canyonlands National Park's Island in the Sky district - attract four-wheel-drive enthusiasts, mountain bikers and adventurous tourists. The trek makes a good half-day trip.

"When it's dry, we say it's a high-clearance two-wheel-drive road," Simmons said. In other words, four-wheel-drive is a good idea, though two-wheel-drive trucks and sport utility vehicles can manage it. Family cars and vans have been seen on parts of the trail, but that might not be a wise option. Motor homes and those towing trailers should not use the Shafer Trail.

People should also take into account, as Simmons put it, "their level of comfort with heights." The drop-off exposures along the rim and on the switchbacks can be, well, nerve-racking. In some places, he said, it's better to be a driver - with some sense of control - than a passenger.

The Shafer can be approached from either side: at the end of U-279, 16 miles from that riverside highway's junction with U.S. 191 near Moab, or from Island in the Sky, via the turnoff to the White Rim Trail, just beyond the new fee station.

The elevation of Island in the Sky's east rim is about 5,900 feet above sea level. From Red Sea Flat, the Shafer Trail drops a thousand feet in about the first half mile, thanks to a half-dozen dizzying switchbacks. The road levels off near Canyonlands' White Rim (which hosts a renowned 100-mile jeep-and-bike trail of its own) and in the Shafer Basin.

At this point, back-road explorers find themselves 1,600 feet below Dead Horse Point, a blocky rusty-red butte towering overhead much of the way, and just above the Goose Neck, a notable Colorado River meander visible from the state park's viewpoints.

Although the road is passable in most weather, it's always best to keep an eye on the sky. Even a light rain will turn washes into raging streams of colored water. If a flash flood threatens, get to safety as soon as possible.

Cliffs along the trail can also be a hazard. A Moab man was killed in a 500-foot fall in 1967 when he stopped to take photographs along the trail and slipped.

The landscape and geology can take your breath away. The fractured buttes - variously buff or brown or lavender or maroon - look as if they were hand-made by giants for purposes only giants would understand.

The visible formations include the relatively young Navajo and Kayenta sandstones ("only" 175 million to 180 million years old) and, nearer the carving Colorado, the Moenkopi, Cutler and Rico layers (laid down 230 million to 275 million years ago). These rocks were once windblown sands, ancient streambeds and lakebeds and primordial coastal seas and tidal basins.

Shively, who travels the country for business - she's a computer software writer - and for pleasure, was entranced by the view a few hundred feet directly above the Colorado River. A tour van out of Moab stopped nearby and disgorged a flock of sightseers, most speaking French.

She envied the guide's chosen field, visiting such splendor every day. If only she had such a job . . . .

"Then," Shively said, "when we'd stop at places like this, I'd say, `Look, we're in my office.' "