He’d been maundering again. Morbid old fool.

With considerable effort on both their parts, Willow managed to clamber onto his back. Longtusk couldn’t help but recall the liquid grace with which Crocus, the Firehead cub, had once flowed onto his back, how they had run and pranced together.

With a deep rumble he turned away and headed up the cold, forbidding slope. His breath steamed, and his aging limbs tired quickly.

The old Dreamer was already snoring gently.

Soon Longtusk neared the crest of a ridge. The snow thinned out, and he found himself walking on rock that was bare or covered only by a scattering of snow. The land flattened out, and he stood atop the ridge, breathing hard.

He was standing on the rim of a crater.

He stepped forward cautiously. It was a great bowl, cut into the Earth, like the imprint of an immense foot. The rim curved around the huge dip in the land to close on itself, a neat circle.

The crater wall, coated with snow and ice, was sculpted to smoothness by the wind, like the sweep of a giant sand dune. The shadows were subtle and soft, white shading to blue-gray — save at the rim itself, where a layer of bare brown rock was exposed. The winds off the ice sheet kept this curving ridge swept clear of new snow falls, so that ice could not form. He let his eye be drawn to the crater’s far side, where there had been an avalanche, and the smooth snow surface was marked by great ripples descending toward the crater’s base.

The floor of the crater was surprisingly flat. He knew there was a lake down there. In the brief summer it would melt, turning into a placid pond of blue-gray water, cupped by the crater, visited by birds — in fact, the geese who had guided him here to the nunatak. If a mammoth were down there now, walking across that frozen surface, she would look no larger than a grain of sand, dwarfed by this immense structure of rock and ice.

Longtusk raised his trunk and trumpeted, high and thin. His voice echoed from the iced-over walls of the crater, and pealed out over the frozen lands around the nunatak.

Willow stirred on his back, grumbling, and subsided back to sleep, clinging to Longtusk’s fur instinctively.

Longtusk walked a little farther around the crater’s rim. He came to a broad ridge in the icebound land, leading away from the crater. He walked this way now, feeling for the firm places in the piled-up snow.

Soon he saw what he was looking for. It was a splash of coal-black darkness, vivid against the snow that surrounded it. This was another crater, but little more than ten or fifteen paces wide. And further craters lay beyond, dark splashes on the snow, as if some wounded, rocky giant had limped this way.

He let himself slide over crunching rubble into the small crater. The rock was warm under his thick footpads. Where snow fell from his coat it melted quickly, and steam wisped up around him. The rock here was fragmented, crumbled. It was jet black, sharp-edged, and the fragments he picked up had tiny bubbles blown into them, like the bones of a mammoth’s skull.

This crater did not have a neat rounded form, no cupped lake in its base. The walls here were just crude piles of frothy black rock. In places he could see flat plates of rock which lay over drained hollows, like the remnants of broken eggs. Everything was sharp-edged, new. This small crater was obviously much younger than its giant cousin nearby. Perhaps these small frothy rocks, frozen fragments of the Earth’s chthonic blood, were the youngest rocks in the world.

And yet even in this new raw place, there was life.

He picked up a loose rock. He tasted moss and green lichen, struggling to inhabit this unpromising lump: sparse, nothing but dark green flecks that clung to the porous stuff — but it was here. And these first colonists would break up the hard cooling rock, making a sand in which plants could grow. Perhaps one day this would be a bowl of greenery within which mammoths and other animals could survive.

He came up here once a year — but always with Willow as his sole companion. Mammoths are creatures of the plains, and the members of his little Clan were suspicious of this place of hills and ice. And there wasn’t a great deal to eat up here. But Longtusk embraced the stark, silent beauty of this place.

For he knew that these craters were a sign of Earth’s bounty — the gift that had created this island of life and safety, here at the heart of the forbidding icecap.

One night — many years ago — the mammoths had seen, on the fringe of their nunatak, a great gush of smoke and fire which had towered up to the clouds. The mammoths had been terrified — all but Longtusk, who had been fascinated. For at last he understood.

Over most of the world, the heat which drove life came from the sun. But here, far to the planet’s north, that heat was insufficient. Even water froze here, making the icecaps that stifled the land.

Instead, here in the nunatak, the heat came from the Earth itself.

In some places it dribbled slowly from the ground, in boiling springs and mud pools. And in some places the heat gathered until it burst through the Earth’s skin like a gorged parasite.

That was the meaning of the great eruption of fire and smoke they had seen. That was why the land was littered by enormous blocks of black rock, hurled there by explosions.

And the craters — even the biggest of them — were surely the wounds left in the Earth by those giant explosions, like scars left by burst blisters. In this small crater he could actually see where smaller bubbles had formed and partially collapsed, leaving a hard skin over voids drained of rock that had been so hot it had flowed like water.

It was the Earth’s heat which had shaped this strange landscape, and it was the Earth’s heat which cradled and sustained the nunatak.

He left the small craters behind and began a short climb to another summit.

Soon he was breathing hard. But he’d been climbing up here every spring since they’d first arrived, and he was determined that this would not be the year he was finally defeated.

He reached the summit. This rocky height, windswept bare of ice like the crater rim, was one of the highest points in the nunatak, so high it seemed he could see the curve of the Earth itself.

All around the nunatak was ice.

The icecap was a broad, vast dome of blue-white, blanketing the land. The ice was smooth and empty, as if inviting a footstep. Nothing moved there, no animals or plants lived, and he was suspended in utter silence, broken not even by the cry of a bird.

Mountains protruded from the ice sheet like buried creatures straining to emerge, their profiles softened by the overlying snow. The mountains — a chain of which this nunatak was a member — were brown and black, startling and stark against the white of the ice. Their shadows, pooled at their bases, glowed blue-white.

Over the years Longtusk had come to know the ice and its changing moods. He had learned that it was not without texture; it was rich with a chill, minimal beauty. There were low dunes and ridges, carved criss-cross by the wind, so that the ice was a complex carpet of blue-white traceries, full of irrelevant beauty. In places it had slumped into dips in the crushed land beneath, and there were ridges, long and straight, that caught the low light so that they shone a bright yellow, vivid against ice. Here and there he could see spindrift, clouds of ice crystals whipped up by the wind and hovering above the ground, enchantingly beautiful.

The ice was a calm flat sea of light, white and blue and yellow, that led his gaze to the horizon. The ice had a beauty and softness that belied its lethal nature, he knew; for nothing lived there, nothing outside the favored nunatak.