Centennial (7 page)

About one million years ago the Ice Age began to send its rapacious fingers down from the north polar ice cap. Because of intricate changes in climate, triggered perhaps by variations in the carbon dioxide content of the earth’s atmosphere or by accumulations of volcanic dust which intercepted the sun’s heat that otherwise would have reached the earth, large sheets of ice began to accumulate where none had been before.

The glaciers invading North America reached so far south and were so thick, they imprisoned water that normally belonged to the oceans, which meant that shorelines which had lain submerged for the preceding millions of years now lay exposed. The great western glacier did not quite reach Centennial; it halted some distance to the north. But at high elevations in the Rockies, small glaciers did form and filled the valleys, and when they moved slowly to lower levels they gouged out the valley bottoms and carved the standing rocks, so that much of the beauty of the New Rockies stems from the work of the glaciers.

They arrived in the mountains at spaced intervals, the first major one appearing about three million years ago; the last, only fifteen thousand years ago. But of course, at high, cold altitudes like the topmost New Rockies small glaciers persisted and still exist.

As the mountain glaciers melted they produced unprecedented amounts of water, which created floods of gigantic proportion. They cascaded down with fierce velocity and submerged traditional rivers, causing them to expand many times their customary width. Much detritus was borne down from the mountains, most of it with sharp cutting edges, and it was this mixture of copious water and cutting rock which planed down the lands to the east.

Sometimes, high in the Rockies, the glacier would impound a temporary rock-and-ice barrier, and behind it an enormous lake would be formed. It would exist for decades or centuries. Then, one day, there would be a violent cracking sound, and with one vast rush the contents of the lake would surge forth, miles wide until it roared into some confining canyon, when it would compress into a devastating liquid missile, shooting along with terrifying force, uprooting every living thing and ripping away huge boulders from the walls of the canyon before rushing at last onto the plains.

There it would reach the river. A wall of water would fan out across the plains, engulfing both the river and its tributaries. Churning, roaring, twisting, it would scour everything before it as it scratched and clawed its way eastward. In the space of an afternoon, such a flood might carve away deposits which had required ten million years to accumulate.

It was the river which had laid down the new land; it was the river which took it away. The endless cycle of building up, tearing down and rebuilding, using the same material over and over, was contributed to by the river. It was the brawling, undisciplined, violent artery of life and would always be.

The major characteristics of land around Centennial were now fairly well determined and there is little more to report. There were, however, four special places of no great consequence in the grand scheme of things but around which much of this story will revolve.

The first was a chalk cliff running north-south some miles northwest of Centennial. Its basic components had been laid down some two hundred and seventy million years ago during that period when the Ancestral Rockies were disintegrating and washing out to sea. At the bottom of this sea huge beds of limestone accumulated in flat layers, one above the other like sheaves of paper in a pile. This limestone was infinitely older than the New Rockies and constituted yet another example of how the earth’s material was used, broken down, accumulated, conserved and reissued in new form.

For about one hundred million years this limestone bed lay flat, sometimes exposed but usually at the bottom of some sea. Then internal turbulence within the mantle uplifted the area so that it stood as high as some mountains. No sooner had it moved into its elevated position than it was visited by a racking accident: a large fault wrenched the surface of the earth, depressed the area and cracked the limestone along its north-south axis. The eastern portion dropped some eighty feet below its previous level, while the western half rose twenty, forming a white chalk cliff about one hundred feet high.

There it stood, one hundred and thirty-six million years ago, a chalky white cliff with a rain forest on its upper plateau and a great swamp bathing its feet, ready for the dramatic incidents which would occur along its margin.

The second place was a moderately high mountain valley to the west of Centennial and slightly to the south. A small stream of water ran the length of the valley before joining the river; it had been the cause of the valley’s existence. The valley was not ancient, for it developed only in the later stages of mountain building; it could not have been any more than forty million years old, but throughout its brief life it had always been a place of exceptional beauty.

It ran almost due east and west and was only a few miles long. Its sides were formed by steep mountains which hemmed it in; it was not wide, the mountain walls being less than a mile apart, and it had a gentle fall, the higher end being at the west. Its beauty was gemlike rather than expansive.

During its existence it had undergone little change. It had started at an elevation of only four thousand feet, but at the great uplifting fifteen million years ago it had been raised to an elevation of ten thousand feet. Subsequent erosion had lowered this to eight thousand, just low enough to make possible one of the features which made it memorable.

On the north wall, which of course received the sun, a thick grove of aspen trees developed about one million years ago to form a thing of joy. The trees heralded spring as it was about to appear, their small gray-green leaves shimmering in the sun. In midsummer their leaves were exquisite, for they were attached to their branches in a peculiar manner which left them free to flutter constantly; the slightest breath of air set the aspen shaking so that at times the entire north wall of the valley seemed to be dancing. It was in the autumn, however, that the aspen came into its true glory, for then each leaf turned a brilliant gold, so that a single tree seemed an explosion of vibrating loveliness. In autumn this valley was a place of beauty unmatched across the entire continent.

But curiously, the valley would take its name from a much different kind of tree, which clustered on the dark south wall where the sun did not shine. It was an evergreen. Now, there were many types of evergreens in the New Rockies; they might be considered the symbolic tree of the region, but the one that grew in this valley was different, for it was not green but a spectacular blue. It was the blue spruce, a tree of dignified proportions and splendid color. It grew much taller than its neighbor across the stream, and larger. And it was not deciduous, so that in late autumn when the aspen stood bare, its golden leaves having vanished one by one, the glory of the blue spruce came into its own. In winter, when clinging snow covered the spruce, allowing patches of blue to show, the valley was a quiet, dreamlike place, so lovely that even passing animals instinctively found refuge here. Throughout the balance of the year the tall spruce trees showed noble coloring, from powdery blue to indigo.

In historic times, the place would be named Blue Valley, a notable setting, well proportioned in all things. If it did not lie at the top of the mountains, it did not hide at the bottom, either. Its stream was capable but never turbulent, and although snow sometimes crowded the floor of the valley, it rarely fell so deep that the valley itself became inaccessible. Under any circumstances this delectable valley, with its gold and blue trees, would have been memorable, but two events made it even more so.

When permanent ice began to form in the highest mountain valleys, it became only a matter of time until some glacier shoved its icy snout into Blue Valley. This happened, and the front edge of the glacier gouged out the bottom lands, widened the base of the valley and scoured the walls of the mountains that enclosed it. Of course, every tree within the valley was destroyed, but ages later, when the ice had receded, the trees reestablished themselves as if nothing serious had interrupted them, and the valley was now much more pleasant than it had been before, since the glacier had carved out a spacious meadow filled on the north bank with aspen and on the south with blue spruce.

Subsequent glaciers broadened the meadow and rearranged the rocks. Each mutilated the trees, but with that fine determination which marks so much of nature, they returned, and by the year 15,000 B.C. the valley had assumed its present form and was a place of enhanced beauty.

The second event happened long before the aspen and blue spruce had given the place its character, and we must go well back in time to understand it. About thirty-five million years ago, a pressure very deep within the mantle sent relatively small amounts of highly liquid magma probing upward at very high temperatures.

It sought out any weakness in the structure of the rock, and was especially inclined to surge into cracks where faces met, expanding them and filling them to the remotest cranny. This had happened often before, as can be seen in any large accumulation of mountain rock: invariably the rock will show where a hot igneous material had intruded itself into interstices, and this has occurred all over the world.

What made this incursion exceptional was that this particular flow of magma contained a high percentage of minerals, sometimes in pure state: galena, silver, copper filled the interstices. The liquid rock that crept into the long pipe underlying Blue Valley contained a large proportion of unalloyed gold.

The end of the pipe it filled lay only ninety feet below the surface of the valley, along the northern flank. It extended downward at an angle of forty degrees for nearly a quarter of a mile. It was not a large pipe, and therefore did not contain any fantastic amount of gold, but it was substantial, and it filled every crevice.

It lay undisturbed for more than thirty million years. When the area rose, it rose too. When minor faults appeared, it adjusted to them. And when the area subsided, the golden pipe fell with it, still ensconced under the north bank of the little stream. In time roots of the golden aspen formed a network above it.

When the first great glacier filled the valley it stripped away some fifty feet of cover protecting the near end of the pipe, but no other change occurred. Each succeeding glacier cut away a little more of the protection until the last one came. Sometime around the year 1,000 B.C. this glacier actually cut away six feet of the pipe and scattered the gold that it had contained along the bottom of the stream for a distance of some two hundred yards.

This same glacier, of course, deposited gravel over the exposed end of the pipe, so that it could not easily be detected, and hid the nuggets of gold that lay at the bottom of the stream. Then trees returned and the gold was buried again, but each autumn when leaves of the aspen turned, this was a valley that was doubly golden.

The third place was conspicuous from all directions, and spectacular, but what was significant about it was hidden, and we shall not know of it till later.

Some sixty-five million years ago—shortly after the emergence of the New Rockies—the river began hauling down an extraordinary amount of rock, gravel and sand, which it deposited in a thick overlay on the flat plains to the east. We have observed this phenomenon before, so there is no need to recapitulate, except to state that at the location we are talking about, a spot to the north of Centennial and slightly to the east, the deposit eventually, was more than two hundred feet thick.

When this process was completed, thirty-eight million years ago, the plains to the east were so built up that they blended harmoniously into the lower reaches of the New Rockies, creating a lovely sweep that extended in unbroken beauty several hundred miles into Nebraska and Kansas. This symmetry did not endure, for the New Rockies experienced a massive uplifting, which raised them above the gentle sweep. As a result, the river now dropped more steeply from the mountains, carrying with it many cutting rocks. It surged eastward and for twelve million years dominated the foothills, cutting them away, scraping down hillocks, and depositing on the plains new layers of soil characterized by a rocky, infertile content.

The great inland sea which had once dominated this area had long vanished, so that the building of this new rock had to be accomplished in open air. The river would bring down deposits, which would spread out in fans. Sun and wind would act upon them, and new deposits would form over them. Gradually, disparate components would begin to solidify, and as heavier forms accumulated on top, those on the bottom would coalesce to form conglomerates.

Each year the plains grew a little higher, a little more stable in their footing. Finishing touches were applied about eleven million years ago, when a sandstone rock was laid down, sealing the entire region. This final rock had a peculiar characteristic: at the spot we are talking about, north of Centennial, some variation occurred in the cement which bound the granular elements together. Different from the cement operating in nearby regions, it had been formed perhaps from volcanic ash which had drifted in; at any rate, it created an impermeable caprock which would protect the softer sandstone that rested beneath.

At last the vast job of building was ended. From the period when the New Rockies underwent their secondary uplift, some three hundred and twenty feet of solid rock and soil had been laid down, all protected by the caprock, and had there been an observer at the time, he could have been excused had he concluded that what he saw then, eight million years ago, would be the final structure of the plains.