Strolling the San Andreas fault is about as down-to-earth as you can get. And entirely otherworldly.

In the Mecca Hills, the fault zone is a putty-colored no man's land of pinnacles and ravines, strewn with a rainbow of rocks washed down from surrounding hilltops. These badlands at the eastern end of the Coachella Valley are just one small section of the 650-mile stretch where the Pacific and North American plates do the bump and grind that Californians know so well.

In truth, I didn't set out to tour a source of California's earthquake nightmares; apart from the famously shaky hamlet of Parkfield in Monterey County, I hadn't a clue where to find the San Andreas fault. I'd just felt a winter trip to Palm Springs coming on and wanted to sample a side of the Coachella Valley that was less golf cart and more Jeep.

Several companies in the area offer desert Jeep tours, and the two I took both turned out to be explorations of the fault zone — which is no coincidence. The San Andreas has been the primary sculptor of the valley's landscape for millions of years.

On a Saturday last month, five strangers rendezvoused in the parking lot of a coffee shop just off Interstate 10 in Palm Desert. Two open-roofed red Jeeps awaited us, as did Gordi — a retired science teacher and a knowledgeable guide for Desert Adventures Jeep Eco Tours. It would be an hour to our first stop on the four-hour Mystery Canyon Tour.

As we drove, first paralleling the interstate and then heading south, Gordi kept up an interesting patter. Stick to the main desert towns — Palm Springs etc. — and the Coachella Valley seems little more than desert veneered with golf greens. Get farther out, however, and it's heavily agricultural. Gordi pointed out the acreage of West Coast Turf, which supplies sod to sports arenas and golf courses around the country. As we cruised past, he identified the fields of carrots, artichokes, potatoes and table grapes, and groves of citrus, pecans and date palms. Indio, we learned, is the polo capital of the western U.S., with tournaments at its two clubs nearly every weekend during the season.

When we'd put developed areas behind us, Gordi launched into local geological history. In prehistoric times, the Gulf of California extended this far north; more recently, Lake Cahuilla covered the valley until about 400 years ago. He pointed out the water level of the old lake, a "bathtub ring" around the base of the nearby mountains.

Soon we turned onto unpaved Painted Canyon Road, which led to our destination — the Mecca Hills Wilderness Area, a maze of eroded rock thrust up by the San Andreas fault's seismic shifts. Gordi identified plants — creosote bush, palo verde, ironwood, smoke tree, honey mesquite — and explained how each was used by the Cahuilla Indians. Sand verbena and desert sunflowers were in unusually early bloom, thanks to the rains.

We piled out for a stroll through the fault gouge — the tortured, crumbling, dun landscape formed as the tectonic plates grind past each other. Before I actually stood on this fractured land, I'd imagined the San Andreas fault as a narrow fissure across an otherwise normal landscape. But the Mecca Hills' fault zone, with its eerie rock formations, is several miles wide. The San Andreas stretches all the way from the Imperial Valley, south of the Salton Sea, to Point Arena in Mendocino County, where it veers off into the Pacific. Even at its narrowest, the fault zone is 100 yards wide.

We got out of the Jeep again at Painted Canyon, less than 10 miles north of the Salton Sea. The name is a little misleading; this isn't the vivid desert color of Arizona or Utah. The walls, formed of rock folded and tilted by quakes, are "painted" more by changing light and shadow than by minerals. Gordi's plan was to hike through the gorge to Ladder Canyon, a smaller side canyon with ladders that ascend to overlooks. But the rains had changed the lay of the land, washing rocks and soil into the gorge. The entrance to the canyon seemed to have disappeared.

It was sort of anticlimactic and maybe a little sedate for a Jeep tour; the roads hadn't even required four-wheel drive. But it had been a congenial afternoon, ending with a stop at Oasis Date Gardens. Gordi really hauled to make it back to the coffee shop by 5 p.m., about blowing our eyebrows off in the process.

After the tour, I met up with my husband, Tony, to check into the Springs, a small, secluded-feeling spa hotel built in 1935 in downtown Palm Springs and renovated in 2003-04. The furnishings were chic, with reproductions of antique French posters in place of the usual hotel art. The bed was extraordinarily comfortable, and although the room was small, the handsome, oversize bathroom easily compensated. After the windburn, it was welcome luxury.

And that's the thing about the Coachella Valley — rugged adventures abut creature comforts. For lunch the next day, for instance, we stopped at the River, a shopping and entertainment complex in Rancho Mirage. The complex, designed by the Jerde Partnership, which is behind such high-profile developments as Universal CityWalk and San Diego's Horton Plaza, incorporates an artificial river that forms a 700-foot "waterfront" along Highway 111.

In Piero's Acqua Pazza, a California bistro there, water ripples down sheets of glass to partition the stylish dining room. The menu offers 100 tequilas, 49 beers and lots of margaritas and martinis, so Piero's clearly lights up after sundown. But it was a lovely spot for lunch too — particularly on the patio, surrounded by the "river" on three sides. Tony and I enjoyed velvety wild mushroom soup, mixed green salad, a white pizza and a tower of avocado and tuna sashimi.

A bumpy, fun ride

For the second tour, Tony tagged along. Again a group assembled at an intersection north of town to meet our guide, Jordan of AAA Five Star Adventures. Although this was another San Andreas tour, along a different section of the fault zone, the trips' similarities ended there. Forget pavement: We headed north, and in minutes we were off-road in a broad, rocky wash.

As we bumped slowly along, Jordan touched on some of the same information Gordi had about the desert environment and ancient Lake Cahuilla. Here and there we'd pass an old car or stove riddled with bullet holes. In a Georgia O'Keeffe moment, we came across the sun-bleached skull and bones of a coyote.

We climbed a canyon in the Indio Hills formed by the crashing tectonic plates perhaps as recently as 1,500 years ago. At one spot, Jordan pointed out the alternately fine and coarse layers of sedimentary rock in the canyon wall. They marked dry years — all sand — and wet ones, when rocks were washed down from above. At another stop, he had us savor the pure silence.

Much as I'd enjoyed the previous day's outing, this was a real taste of off-roading — ruts, rocks and all. Out of the Jeep, we explored slot canyons on foot, some barely wide enough to squeeze into. There was a much keener sense of adventure and exploration — this was fun.