IN WHICH A SOLITARY SKIER TRAVERSES THE ICY REMAINS OF A GLACIAL EPOCH

A nameless range of hills runs across the U.S. from central Montana as far east as Long Island. Like a Great Wall whose origins lie in the distant past, this rim of earth outlines the farthest advance of the last great ice sheet of the Ice Age. Retreating north 10,000 years ago, the glaciers left behind a moraine, a belt of hills and hollows with Middle-Earth names like kettles and kames and eskers. Even in New York City one can see the imprint of glaciers on the ice-eroded rock outcroppings of Central Park. But the best place to track down the ice sheet is in Wisconsin, where the 1,000-mile Ice Age Trail follows the moraine across the state. And the best time to do so is in the dead of winter.

The Ice Age Trail was conceived in the mid-1950s, the brainchild of Ray Zillmer, a Milwaukee attorney. Zillmer had spent a lifetime hiking the moraine and was concerned about its gradual transformation into sand and gravel quarries and subdivided property. He proposed the creation of a national park stretching along the moraine from the shore of Lake Michigan, near Sturgeon Bay, Wis. to the banks of the St. Croix River on the Minnesota border. Not surprisingly, a National Park Service feasibility study concluded that the problems posed by a park two miles wide and 1,000 miles long were insurmountable.

In 1964, three years after Zillmer's death, a compromise bill was pushed through Congress by Henry S. Reuss (D., Wis.), an early supporter of the trail. The bill established a nine-unit Ice Age National Scientific Reserve, the first noncontiguous park ever proposed by the National Park Service, and authorized creation of a hiking trail that would follow the moraine, linking the Reserve units together like beads on a string.

A wall map in the office of Adam Ca-how at the University of Wisconsin-Eau Claire shows the progress of the Ice Age Trail in blue marking pen. There are noticeable gaps. Cahow, a geography professor and a member of the Ice Age Trail Council, has personally brushed the trail through northern Wisconsin. Most of it runs through public land, and where easements couldn't be obtained, the trail is routed to the nearest roadway and designated Ice Age Bicycle Trail.

But a 10-speed doesn't seem right for touring the remains of an ice sheet. I wanted to ski the moraine in winter when imagining glaciers of a bygone era would be easy. I asked Cahow to recommend a section of trail suitable for a four-day skiing-camping trip.

He pointed to a diagonal line running west to east across the Chequamegon National Forest in Taylor County, about dead center on the map.

"You couldn't ask for prettier or more varied terrain," he said. "At 40 miles, the Chequamegon is likely the longest wild stretch of trail we've laid out."

Cahow cautioned me that the trail hadn't been designed primarily for cross-country skiing. "Travel slow, expect to run into steep slopes and sharp turns, don't expect to make good time," he said. "And January can be very cold."

The winter had been unseasonably warm, however, and I was worried that the snow would melt before I could begin. But it did not, and four days later Gil Tanner and I were driving north. Tanner, a former president of the Ice Age Trail Council, had invited me to ski a stretch of the trail with him to his cabin north of Bloomer. We had started in the late afternoon and now the light was failing.

"This is dead-ice moraine, formed after the ice quit moving," Tanner said. "The whole area is just full of ice-block lakes. Chunks of ice would break off the glacier and be covered by debris. When the ice melted, the ground settled into a depression and filled with water."

It was nearly dark when we parked at the trailhead, strapped on our skis and struck off down a sunken logging road. Gil led the way. A man in his late 50s with the frame and demeanor of a football coach, he scrambled up inclines on skinny skis, then descended blindly, his voice booming instructions in the darkness: "Watch it here! Look out!"

I was skiing, more or less by feel, my strides tentative and exploratory. Gradually I began to suspect that Tanner, who was in fact the cartographer who had mapped the trail, didn't actually need to see his way.

A yellow light shone ahead in the woods, and I decided it was a lantern Tanner had set as a beacon in the window of his cabin. But as I skied on, the light grew enormous and rose at an angle through the treetops until it became a full moon. Shortly the trail was awash in moonlight, and Tanner was waiting ahead where the logging road gave way to snow-covered swamp.

"It's only been 11,000 years since the last glacier retreated here," he said. "The landforms are still fresh enough that you can imagine the ice sheet just north of here. In winter you don't have to imagine very hard."

We herringboned up a hogback ridge, skiing along its spine to a tall stand of white pine where Tanner had built his A-frame. By now the moonlight was bright enough to read by, but the inside of the cabin was dark and cold. We banged around blindly until Tanner lit a Coleman lantern and hung it from a loft beam, Then we brought in lengths of birch and popple (as we call poplar out here), which Tanner shoved into the woodstove until he had to kick the door to shut it. He doused the wood with white gas and fired it up.

Off came the parkas, sweaters and hats. Tanner put a coffeepot on the stove, then sat back, legs splayed out, basking in the radiant heat.

"My father bought this land for a woodlot back in 1932, at the bottom of the Depression," he said. "Paid a dollar an acre for it. We were burning wood for heat then, and my dad and I would drive up nearly every weekend in a Model A Ford pickup with a square-box bed and cut wood. There was an old guy living up here and he had a pair of horses that would help us snake the logs out of the woods to the road. I hated it."

We looked out the large triangular window and saw that the moon had climbed nearly to the roof peak, and I asked Tanner why he'd come back after so many years and built the cabin here.

"Because I find the land a lot more interesting knowing how and why it was formed," he said. "The ridge this cabin is built on is probably a crevasse-fill. As the glacier waned, meltwater poured into the crevasse, filling it with sediment, so that when the ice disappeared nothing remained but the ridge."

He seemed pleased with the glacier he had conjured up, placing us in its fissured depths. Despite the slight vertigo these sudden transitions caused, I envied Tanner's vision. He seemed to straddle the past and the present effortlessly, speaking of glacial epochs in the same breath that he spoke of his childhood, as if both had shaped his destiny equally.

On the second day of my cross-country trip through the Chequamegon, I skied alone. The temperature was—10° without wind, and the untracked powder spilled over my skis. Making turns was easy, but then a nice downhill chute would dead-end in a sunken creekbed or veer sharply at a 90-degree angle. The uphills were dishearteningly steep. Part of the problem was that I was towing too much gear on a homemade travois, a plastic sled attached to my hip belt by two fiber-glass wands. Hauling the travois uphill was like pulling a dead man.

Despite the extreme cold, I was sweating. Halfway up a steep incline, I had to remove my balaclava helmet so my hair wouldn't become soaked and later freeze. Mittens were next. By removing or adding layers of clothing, I could adjust my body's thermostat to maintain a rough equilibrium. Still, I was perspiring too much. To prevent dehydration, I took swigs of lemonade from a plastic bottle that hung from a cord inside my sweater and windbreaker. By noon the lemonade had chilled to yellow slush.

At 1,400 feet the trail skirted the crest of a hill. The sky was clear and so permeated with sunlight that my eyes ached. From this height, the advantages of skiing the trail in winter became obvious. With the trees bare, the jumbled contours of the land and their glacial lineage can be easily read. In July I had hiked here with my family, leery of black-flies and woodticks and walking in what seemed to be a green tunnel. Now the view extended for miles: north to the Perkinstown Lookout Tower and the range of rounded white hills ringing ice-covered lakes in hollows deep as craters.

This round wooded hill was, like many of the others, a kame—a hole formed in the glacier in which melting ice deposited the sand and gravel it carried to form an almost perfectly symmetrical mound. Because their slopes are so even, kames are often used for downhill skiing. With this in mind, I began my descent through a popple stand, hoping the sled wouldn't catch on a tree. The going was fast. In the hollow at the bottom of the hill, a diversity of animal tracks converged in what must be, during the hours of darkness, heavy traffic. The moraine's up-and-down terrain fosters a wide range of vegetation and wildlife. One finds snowshoehare tracks in the cedar swamps and on the hardwood ridges are the fanned wing marks of ruffed grouse.

When he laid out the Chequamegon section of the Ice Age Trail, Cahow drew a pencil line on a topographical map and hiked the route to see if it was workable.

"Many times, I'd find there was already a trail, a deer trail," he had told me. "Animals lay out trails along the contours of hills exactly as a person would to minimize slope and effort. They seek the path of least resistance."

Clearly there's a question as to whose trail this was, as for some time I'd been following fresh deer tracks, the heart-shaped hooves dragging through the snow in no particular hurry. Visible finally in a stand of hemlock, a pair of does gave me a last go-to-hell look before bounding away. I watched as their white tails flickered off into the pine swamp.

The trail crossed the South Fork of the Yellow River on an ancient beaver dam with open water running at its edge. I broke off a piece of ice to suck on and, heading north, followed the yellow blaze marks on the trees, unsure whether the ridge I was striding along was an esker (a winding protrusion of sand and stone formed by deposits of sediment in the beds of streams that flowed through or beneath glaciers) or an abandoned railroad grade. Narrow-gauge railroads opened huge virgin forests of hemlock and white pine to logging in the 1890s. Before the forests were reduced to stumpage, they were frequented by Indian tribes and by trappers and missionaries. In 1661 Father Renè Mènard, a French Jesuit, was canoeing in this area when he stepped ashore to search for a portage route and was never seen again.

But if this ridge were an esker instead of a railroad grade, it is a considerably older hill of stone, having been formed by a subglacial stream 11,000 years ago. And against that long expanse, the gap between Father Mènard's passage and my own was slight indeed.

By five in the afternoon the sun was behind the hills and the cold seemed to rise from the ground. My tent was pitched in a hollow protected from the wind, and after changing into a down parka and booties I walked about gathering firewood feeling as insulated and alone as a moonwalker. Now came the best part of winter camping—replaying Jack London's short story, "To Build a Fire." Though I had a Svea stove in reserve to melt snow for water, a campfire would provide both warmth and companionship. Shoveling out a pit in the snow, I laid down curls of birchbark, then pine twigs, sticks and finally logs. My bare fingers fumbled with the match, but then the birchbark ignited in oily smoke and soon a fire was roaring. After a boil-in-the-bag supper, I fed the fire another log and myself some 90-proof brandy. It went down like liquid heat. The temperature was 15° below zero, and in the faint light of the moon, the snow had the bluish cast of glacial ice.

I awoke at dawn after a fitful sleep and fixed breakfast. The down-filled mummy bag had been warm but too constricting, and I awoke often during the night, not from the cold but from vivid dreams of live burial. Repacking the sled, I was off again, skiing hard to warm up. The trail recrossed the Yellow River on a puncheon bridge and veered northeast through a hardwood forest broken by flat-topped hills. Called perched lake plains, these truncated hills were once the bottoms of ice-walled lakes on the surface of the glacier. As the glacier melted, the lakes filled with sediment until only the lake bottom remained elevated.

Atop one of these hills, the wind chill became appreciable, as if the gusts were coming off the ice pack. I had become aware of a growing numbness in my left index finger where the wool lining of my mitten had worn thin. Removing the mitten, I stuck the finger in my mouth to revive it. It felt disconnected from the rest of my hand, like a lump of wax. Slowly, feeling returned in a wave of prickly pain, a sign that frostbite hadn't occurred.

By noon I'd covered perhaps four more miles of undulating trail. I set a lunch of venison sausage and cheese on a granite boulder, a souvenir of Canada's Laurentian Plateau that was carried along and laid down in this oak forest by a long-vanished glacier. Among the farms bordering the Chequamegon were smaller granite stones stockpiled along fencerows or set into the foundations of tottering barns.

The incongruity of such enormous rocks, called erratics in geologic terminology, existing far from their native bedrock, triggered a heated scientific debate in the last century. The most popular theory held that the boulders had been moved hither and thither by the Great Deluge of Noah. A variation of this idea was that icebergs had rafted the erratics about when the sea level had been much higher. But the most preposterous explanation, the most incredible, came from Louis Agassiz, a young Swiss naturalist, who told the Swiss Society of Natural Sciences in 1837 that all of Europe had been covered by a massive sheet of ice!

Agassiz was familiar with the effects of glaciers in the Swiss Alps and recognized ice-eroded landmarks far from the mountains. His explanation was that in an earlier time, glaciers had wandered far from their modern haunts in mountain redoubts. While not the first to propose glaciation as the mover of erratics, Agassiz gave the world its first look at the Ice Age.

Snow was falling as I made my last camp on an esker ridge overlooking the frozen Mondeaux Flowage. The-light dusting didn't interfere with my fire building. The ice fishermen had all gone home, and I was thinking about how nice it would be to return here in the summer and fish for muskellunge.

How easily we accept the certainty of seasons, and feel assured that winter necessarily gives way to spring when seasonal change is in reality a constant struggle. What if, as occurred during the Pleistocene epoch, winter never left?

Pleistocene wasn't one interminable cold snap but four separate stages when winter won out over milder seasons and glaciers began to march. The most recent stage is called the Wisconsin because the ice sheet left its imprint so visibly in that state. But many scientists believe we are still in the Pleistocene, living in an interglacial lull.

"A surprisingly small reduction in temperature could start glaciers advancing again," Tanner had told me. "We're only talking about a 5° to 10° change in the mean annual temperature, say from 58° to 53°. Once a winter climate is established—if, for example, the snow doesn't melt one year—we're on our way to another ice age."

Even if the glaciers are coming, I'm not very anxious to buy that desert rancho in The Sunbelt. Winter offers its own rewards, and one of these is snow-camping. After the fire is made, dinner boiled and eaten, the woodpile and the last of the brandy loom ahead as the evening's entertainment. In the dark woods a coyote howls. Other coyotes join in until the night rings with their wailing. Heard alone on a winter's evening, the howling seems at once alarming and melancholy, like some primordial country music played on the listener's nerve endings.

The coyote and the black bear are the last vestiges of wildness in Wisconsin. But in the boreal forests near the ice sheet there were giants in the earth whose very names spoke of hugeness. Where are they now, the woolly mammoth and the mastodon? Gone slouching off to extinction while punier beasts survived on their cunning and wit, beasts like the coyote and man. In the long winters of the Ice Age, man acquired language, in a sense learned to be human. Surely another ice age wouldn't undo that.

In the morning I would ski across the lake to the end of the trail and return to living in a house and sleeping in a bed. But before I climbed into the tent for the last time, I finished the brandy and howled just a little, to show the coyotes I hadn't forgotten how.

ILLUSTRATION

GLENN WOLFF