The Grand Canyon's Secret Network

Rafting down the Colorado River is nothing to sneeze at, but the real excitement is to be found in the hundreds of side chasms

FEELING GROOVY | A view of the Colorado River from an unnamed side canyon

TALK OF LAVA FALLS , the Grand Canyon's most infamous rapid, began months before our departure. Members of my group couldn't believe we were going to brave the very same boat-munching Class V white-water that forced John Wesley Powell, the geologist who explored Arizona's Grand Canyon in 1869, to scramble to shore.

When it comes to a raft trip along the Grand Canyon's Colorado River, rapids like Lava Falls, Crystal and Horn Creek are a mandatory part of the adventure. Yet the majority of my 138-mile journey down the river turned out to be on flat water. Our rafts bucked through Lava's churning turbines in about 40 seconds. Forty seconds out of 14 days.

The real excitement happened on the sidelines, in the network of about 75 named—and countless unnamed—side canyons and gorges. These unsung passages function as the smaller veins feeding into the main artery of the Grand Canyon, the up-to-18-mile-wide, mile-deep gash in the earth through which 227 miles of the Colorado River snakes.

Cruising down the river from one campsite to the next, looking up between oar strokes to ogle the canyon walls, is the outdoorsy equivalent of riding around a new city in an open-air tour bus. You might glimpse an intriguing neighborhood, but there's no opportunity to poke around.

Rafts at the point where the Colorado River meets Havasu Creek.

Slowing down to explore the side canyons is a first-rate way to pack extra adventure into a classic American trip, as well as to fully absorb the area's geological diversity. The mineral composition of each of the Canyon's 15 dominant layers influences the stone's color, type and texture—a variety that is all the more evident on the side-canyon detours. We were a group of 14 experienced outdoors people (including a former river guide), and we knew to make the side canyons our top priority.

Two days into the journey and 19 miles from the starting point, we secured our three boats at the shore and followed a sandy trail up the steep embankment. We wound past cactuses and scrambled up rock terraces as we made our way toward the narrow ravine of Elves Chasm, one of the Grand Canyon's most picturesque side canyons. "You sure you've got enough rope? It looked like a long way down," a hiker said to our group as we crossed paths.

Most people who visit Elves Chasm simply hike a quarter mile to its base, check out its stunning waterfall—an oasis of bright green in a parched land of cactus and scrub—and immediately return to the river. But we had opted for a three-hour route that carried us to the top of Elves Chasm. We then began our descent back to the river, scrambling down natural staircases sculpted in an ancient seabed. About a third of a mile from the canyon top, we came upon a 150-foot natural rock arch with a keyhole view of the river far below. I felt like I was staring down at my very own secret.

traversing Havasu Creek.

Just below the arch, we rigged the climbing ropes for the first rappel—a sheer 200-foot drop that paralleled a waterfall. Once everybody was on safe ground, we continued to move through the chasm, wading through emerald pools and groves of horsetail. This lush vertical landscape stood in astonishing contrast to the arid land below.

The next detour on our list was Blacktail Canyon, just 4 miles away. The tan slopes surrounding the small slot were littered with blooming barrel cactuses.

The Grand Canyon is considered one of the seven wonders of the world, and geologists strain to unravel its mysteries, especially the one commonly referred to as the Great Unconformity. While 1.84 billion years worth of rock make up the Grand Canyon, the 1.2 billion years between Cambrian and Precambrian times are unaccounted for. I'd heard about this puzzle, but here it was writ large on the wall. The varnished buff of the 545 million-year-old Tapeats Sandstone and dark 1.8 billion-year-old Vishnu Schist butted against each other in stark contrast.

We continued our regimen of rowing our boats from campsite to campsite and exploring up to two side canyons a day. A sense of nostalgia began to set in. People wait years to receive a permit from the National Park Service to raft the Grand Canyon on a private trip such as ours. My journal was nearly full and I'd filled multiple memory cards with photos. My time would soon be up.

On day six, we hiked a loop through Deer Creek, home to the famed narrows—a tight side canyon of curving walls that can only be descended by multiple rappels. We made our way down the rock and landed in a shallow pool of water.

The slot in the walls overhead was just wide enough to allow slices of sky to peek through. Golden light dripped from the tawny walls, wiping away my fear of getting swept away in a flash flood. Now I was overwhelmed by the awe that comes with finding yourself somewhere so beautiful.

Hanging on the final rappel, our only means of exit from the narrows, I was surrounded by moss and tangerine monkey-flowers. The Colorado River sparkled far below.

Twenty miles downstream, just when I thought I'd fulfilled my lifetime allotment of beautiful places, we stopped at Havasu Creek, whose electric-blue water puts the Colorado River's brown murk to shame. We hiked through smooth terraces of white rock, framed by Havasu Canyon's bright red walls and a Disney DIS +1.90% -blue sky. I could have kept walking along this route for days.

We had only scratched the surface. But there was so much left to see: the petroglyph panel and natural arch in Tuckup Canyon; ruins on Nankoweap Trail; and Travertine Canyon, with its series of waterfalls tumbling over travertine deposits.

For some people, Grand Canyon trips are a lifestyle. They return to the river again and again like pilgrims. I had never understood this mentality—wasn't there a whole world of rivers worth rafting? But that was before my two weeks exploring the Canyon's chasms. I only got to explore 11 of them. That leaves many, many more to go.