Centennial by James A. Michener Read Free Book Online Page B

subsequent events which we shall observe, blocks of this basement rock will be pushed upward, where they can be inspected, and tested, and analyzed, and even dated. At other memorable spots throughout Colorado this incredibly ancient rock will be broken by faults in the earth’s crust, and large blocks of it will be uplifted to form the cores of present-day mountain ranges.
    It is beautiful to see, as it sticks its head into daylight, a hard, granitic pink or gray-blue substance as clean and shining as if it had been created yesterday. You find it unexpectedly along canyon walls, or at the peaks of mountains or occasionally at the edge of some upland meadow, standing inconspicuously beside alpine flowers. It is a part of life, an almost living thing, with its own stubborn character formed deep in the bowels of the earth, once compressed by titanic forces and heated to hundreds of degrees. It is a poem of existence, this rock, not a lyric but a slow-moving epic whose beat has been set by eons of the world’s experience.
    Often the basement rock appears not as granite but as unmelted gneiss, and then it is even more dramatic, for in its contorted structure you can see proof of the crushing forces it has undergone. It has been fractured, twisted, folded over to the breaking point and reassembled into new arrangements. It tells the story of the internal tumult that has always accompanied the genesis of new land forms, and it reminds us of the wrenching and tearing that will be required when new forms rise into being, as they will.
    It must be understood that basement rock is not a specific kind of rock, for its components change from place to place. It has been well defined as the “layer of rock below which lies ignorance.” In some places it hides far below sea level; at others it marks the tops of mountains fourteen thousand feet high. Throughout most of the United States it lies hidden, but in Canada it is exposed over large areas, forming a shield. Nor was it all laid down at the same time, for variations in its dating are immense. In Minnesota it was deposited more than three and a half billion years ago; in Wyoming, only two and a half billion years ago; and in Colorado, only a few miles to the south, at the relatively recent date of one billion seven hundred million years ago.
    After the basement rock had been accumulated at Centennial, later than almost anywhere else in the United States, one of the most extraordinary events occurred. About two billion years of history vanished, leaving no recoverable record By studying other parts of the west, and by making shrewd extrapolations, we can construct guesses as to what must have happened, but we have no proof. The rocks which should have been at hand to tell the story have either been destroyed beyond recognition or were never deposited in the first place. We are left in ignorance.
    This situation is not confined to the small area around Centennial, although there the gap is spectacular. At no spot in North America have we been able to find an unbroken sequence of rocks from earliest basement to recent sediment. Always there is a tantalizing gap. Over short distances it can have amazing variations in time and extent; for example, during the missing years at Centennial, massive accumulations of granite which would later form Pikes Peak were being assembled only a few miles to the south.
    For hundreds of millions of years at a time Centennial must have lain at the bottom of the sea which at intervals covered much of America. The grains of sediment, eroded from earth masses remaining above sea level, would drift in silently and fall upon the basement, building with infinite slowness a sedimentary rock which might ultimately stand five thousand feet thick.
    At other intervals the new-forming land would rise from the sea to be weathered by storm and wind and creeping rivers long vanished. This cycle of beneath-sea, above-sea was repeated at least a dozen times; repeatedly