It is a typically dry, snow-dusted morning in northern Canada, lit by a hazy arctic sun poised just above the horizon. Trucker Dale Christiensen, in his cab with the window half down, figures it's-35°F outside, not counting the windchill. Peering ahead, he steers his flatbed rig off the gravel road and onto the frozen surface of Great Slave Lake, some 50 miles west of Yellowknife (pop. 14,000), capital of the vast Northwest Territories. As the 40-ton 18-wheeler lumbers onto the wide swath of highway between two ridges of plowed snow, the ice cracks with a series of sharp, staccato pops, and a jagged web of spidery fissures radiates from beneath the wheels. Christiensen, 32, a 10-year-veteran ice-road hauler, shrugs and rolls up the window. "That ain't nothing," he says. "What you gotta watch out for is water on the road. If it's coming up through the cracks, it can get real slippery. You end up spinning, lose control, and in the drink you go. Take a bath with your whole truck. Just gotta take it real slow—20 miles an hour, tops."

Christiensen is one of the first truckers out on the lake routes being plowed and graded for the intense, winter hauling season—the 12 weeks beginning in mid-January when the ice thickens from one to as much as five feet. Plying some of the most remote and treacherous roads in North America, such truckers are a key force in pushing development to the continent's forbidding last frontier. Traversing the frozen lakes of the Canadian North, they are able to haul 50-to 60-ton loads of fuel, heavy equipment and ore-crushing steel balls to remote gold mines that would be far more costly to supply by air. This risky and remarkable enterprise—run by Robinsons' Trucking Ltd., the region's major hauler—demands the roughneck skills of some 360 drivers and the use of about 700 equipment units, including 26-wheel tandem rigs, graders, plows, light planes and a helicopter.

This year the company will supply two sites belonging to Echo Bay Mines—the Neptune mine, in the hilly "bush country" 270 miles north of Robinsons' Yellowknife headquarters, and Lupin, 370 miles away in the blizzard-ridden barrens near the arctic circle. More than $180 million in gold is expected to be extracted from the mines this year. In a good season, the truckers, most of whom come from Canada's southern provinces, can each net about $4,500 a month by making continuous, solo, two-to four-day round-trip runs to the mines—two-thirds of the distance over ice. They follow a strict set of safety rules and carry a three-day supply of food and water, plus a portable gas heater in case they find themselves stranded with a dead engine. Near Lupin, whiteout blizzards may cut visibility to inches, burying the road and dropping the temperature to 60 below. "It scares some of the guys, and they quit," says Christiensen, who unlike most drivers lives year-round in Yellowknife. "But I don't mind. The main thing is, you gotta respect the ice. Don't abuse it, 'cause it pays your paycheck."

Today he is transporting a "picker," a giant cranelike contraption to retrieve a 24-ton bulldozer that broke through the ice two days earlier. "The driver's lucky—it only went down in eight feet of water," he says, pointing out that in previous years trucks and other equipment have plunged to 100-foot depths. "We've never lost a man. Most of us get to where we can pop out of a cab in three seconds if we think she's going down."

Christiensen explains that drivers travel over scores of lakes in convoys of three or four rigs a quarter mile apart, spreading out the weight to minimize the danger of dreaded "blowouts"—sudden, explosive ice breakups that leave gaping holes in the surface. As the trucks cross the ice, depressing it by a few critical inches, they start waves that push ahead beneath the surface, heaving up the roadway like a huge water bed. When the wave hits the shoreline, it rolls back and crashes into other oncoming waves, sometimes resulting in geyserlike blowouts. "We drive slow, keep in touch by radio," says Christiensen, "just to let the guy behind know if anything interesting's ahead—cracks, holes, caribou herds, wolves, whatever."

Christiensen says that some days he hauls to the mines, while other days his brother-in-law Marvin Robinson, the company president, will ask him to do odd jobs such as today's salvage work. Robinson—whose sister Karen is married to Christiensen—is also the company's best ice dynamiter and diver. "Marvin's great in a dry suit," Christiensen says admiringly. "Doesn't think twice about going down 90 feet to hook a line to a rig. Like a lot of us, he loves the challenge."

By the time Christiensen halts his big diesel, Robinson has surveyed the salvage site and is waiting by a pickup truck. "Time to get cold," Christiensen says, leaving his engine running and joining the other men—including two from a government fisheries agency who are on hand to guard against fuel spillage and environmental damage. Over the next four hours, the crew uses dynamite to free the bulldozer, frozen in ice up to its roof. Then they hoist the big Cat out of the icy mush with the picker and winch it onto a flatbed. With only five hours of daylight to work in, they have finished before the last pink glow fades in the southern sky.

"Burned some calories," says Christiensen, wrestling off layers of clothes in the cab, then rubbing life into his fingers. "I could eat a moose." Instead, he lights a cigarette, shifts into gear and settles for a ham-and-cheese sandwich. A miner's son, he talks of growing up in the North, of working in a gold mine himself at 16, of his wife, a Robinsons' office worker, and his children, Alan, 6, and Bonnie, 10. "Most guys are on the road all the time, living in their rigs," he says. "I'm lucky, I get to go home and spend some hours every few days with my family."

As the truck nears land on the way back to Yellowknife, the ice begins crackling and popping again. The wind has picked up, sending swirls of powdery snow across the headlight beams. "All in all, it ain't too bad a life," says Christiensen. "Just gotta drive a little scared is all—and dress warm."