The Plains of Passage - Jean M. Auel [430]
Ayla expelled her breath explosively. She hadn’t known she was holding it. “Jondalar! It’s magnificent! Why didn’t you tell me? I would have journeyed twice the distance just to see this,” she said in an awed voice.
“It is spectacular,” he said, smiling at her reaction, but just as overwhelmed. “But I couldn’t tell you. I’ve never seen it like this before. It’s not often this still. The blizzards up here can be spectacular, too. Let’s move while we can see the way. It’s not as solid as it seems, and with this clear sky and the bright sun, a crevasse could open up or an overhanging cornice give way.”
They started across the plain of ice, preceded by their long shadows. Before the sun was very high, they were sweating in their heavy clothes. Ayla started to remove her hooded outer fur parka.
“Take it off, if you want,” Jondalar said, “but keep yourself covered. You can get a bad sunburn up here, and not just from above. When the sun shines on it, the ice can burn you, too.”
Small cumulus clouds began to form during the morning. By noon they had drawn together into large cumulus clouds. The wind started picking up in the afternoon. About the time Ayla and Jondalar decided to stop to melt snow and ice for water, she was more than happy to put her warm outer fur back on. The sun was hidden by moisture-laden cumulonimbus that sprinkled a light dusting of dry powder snow on the travelers. The glacier was growing.
The plateau glacier they were crossing had been spawned in the peaks of the craggy mountains far to the south. Moist air, rising as it swept up the tall barriers, condensed into misty droplets, but temperature decided whether it would fall as cold rain or, with just a slight drop, as snow. It was not perpetual freezing that made glaciers; rather, an accumulation of snow from one year to the next gave rise to glaciers that, in time, became sheets of ice that eventually spanned continents. In spite of a few hot days, solid cold winters in combination with cool cloudy summers that don’t quite melt the leftover snow and ice at winter’s end—a lower yearly average temperature—will swing the balance toward a glacial epoch.
Just below the soaring spires of the southern mountains, too steep themselves for snow to rest upon, small basins formed, cirques that nestled against the sides of the pinnacles; and these cirques were the birthplaces of glaciers. As the light, dry, lacy snowflakes drifted into the depressions high in the mountains, created by minute amounts of water freezing in cracks and then expanding to loosen tons of rock, they piled up. Eventually the weight of the mass of frozen water broke the delicate flakes into pieces that coalesced into small round balls of ice: firn, corn snow.
Firn did not form at the surface, but deep in the cirque, and when more snow fell, the heavier compact spheres were pushed up and over the edge of the nest. As more of them accumulated, the nearly circular balls of ice were pressed together so hard by the sheer weight above that a fraction of the energy was released as heat. For just an instant, they melted at the many points of contact and immediately refroze, welding the balls together. As the layers of ice deepened, the greater pressure rearranged the structure of the molecules into solid, crystalline ice, but with a subtle difference: the ice flowed.
Glacier ice, formed under tremendous pressure, was more dense; yet at the lower levels the great mass of solid ice flowed as smoothly as any liquid. Separating around obstructions, such as the soaring tops of mountains, and rejoining on the other side—often taking a large part of the rock with it and leaving behind sharp-peaked islands—a glacier followed the contours of the land, grinding and reshaping it as it went.
The river of solid ice had currents and eddies, stagnant pools and rushing centers, but it moved to a different time, as ponderously slow as it was massively huge. It could take years to move inches. But time didn’t matter. It had