squeezed so severely that it was entirely eliminated. The continents came into actual contact, so that such living things as then existed could move from America to Africa and back again over land.
As the inexorable collision continued, there had to be some kind of dislocation along the edges that were bearing the brunt. It seems probable that the edge of the African plate turned under, its rocky components returning to the crust and perhaps even back into the mantle. We know that the edge of the American plate was thrust upward to produce the Appalachian Mountains, not some ancestral Appalachians, but the roots of the very mountains we see today.
After some twenty million years of steady growth the Appalachians stood forth as a more considerable range than the Ancestral Rockies had been. They were, of a certainty, some of the world’s most impressive mountains, soaring thousands of feet into the air.
Inevitably, as soon as they began to emerge, the tearing-down process commenced. First the continental plates drifted apart, with Africa and the Americas winding up in roughly the positions they occupy today. The Atlantic Ocean as it exists today started to develop, its deep inclines providing a basin for the catchment of rock and silt eroded from the heights. Volcanoes operated and at intervals enormous fractures occurred, allowing vast segments of the range to rise while others fell.
As early as a hundred million years ago the Appalachians—only a truncated memory of their original grandeur—began to assume their present shape; they are thus one of the oldest landscape features of the United States. At this time the Appalachians had no competition from the Rocky Mountains, for that range had not yet emerged; indeed, most of America from the Appalachians to Utah was nothing but a vast sea from which substantial land would rise only much later.
The Appalachians play no further part in this story—except that a stubborn Dutchman who grew up along their Bank will travel westward to Centennial in his Conestoga—and in their present condition they seem a poor comparison to the Rockies. They are no longer high; they contain no memorable landscape; they do not command great plains; and they are impoverished where minerals like gold and silver are concerned. But they are the majestic harbingers of our land; they served their major purpose long before man existed, then lingered on as noble relics to provide man with an agreeable home when he did arrive. They are mountains of ancient destiny, and to move among them is to establish contact with a notable period of our history.
They have been mentioned here to provide a counterbalance to the great things that were about to happen in the west. About seventy million years ago much of the western part of America lay beneath a considerable sea, and if this configuration had persisted, the eastern United States would have been an island much like Great Britain, but dominated by the low-lying Appalachians.
But beneath the surface of the inland sea great events portended. The combined weight of sediment and water, pressing down upon a relatively weak basin area, coincided with an upsurge of magma from the mantle. As before, these magmatic pressures from below pushed upward huge blocks of the basement, and bent the more flexible layered rocks above the basement until a massive mountain range had been erected. The range, running from northern Canada almost to Mexico, was both longer and wider than the Ancestral Rockies had ever been and placed somewhat farther east. Its major elevations stood very high, and as these areas were uplifted, the inland sea was drained off.
The mountain range was composed in part of rock that had formerly been utilized in the Ancestral Rockies—which is why we know so much about those ancient mountains we have never seen—and formed one of the world’s major structural forms, which it still does.
The Rockies are therefore very young and should never be
As the inexorable collision continued, there had to be some kind of dislocation along the edges that were bearing the brunt. It seems probable that the edge of the African plate turned under, its rocky components returning to the crust and perhaps even back into the mantle. We know that the edge of the American plate was thrust upward to produce the Appalachian Mountains, not some ancestral Appalachians, but the roots of the very mountains we see today.
After some twenty million years of steady growth the Appalachians stood forth as a more considerable range than the Ancestral Rockies had been. They were, of a certainty, some of the world’s most impressive mountains, soaring thousands of feet into the air.
Inevitably, as soon as they began to emerge, the tearing-down process commenced. First the continental plates drifted apart, with Africa and the Americas winding up in roughly the positions they occupy today. The Atlantic Ocean as it exists today started to develop, its deep inclines providing a basin for the catchment of rock and silt eroded from the heights. Volcanoes operated and at intervals enormous fractures occurred, allowing vast segments of the range to rise while others fell.
As early as a hundred million years ago the Appalachians—only a truncated memory of their original grandeur—began to assume their present shape; they are thus one of the oldest landscape features of the United States. At this time the Appalachians had no competition from the Rocky Mountains, for that range had not yet emerged; indeed, most of America from the Appalachians to Utah was nothing but a vast sea from which substantial land would rise only much later.
The Appalachians play no further part in this story—except that a stubborn Dutchman who grew up along their Bank will travel westward to Centennial in his Conestoga—and in their present condition they seem a poor comparison to the Rockies. They are no longer high; they contain no memorable landscape; they do not command great plains; and they are impoverished where minerals like gold and silver are concerned. But they are the majestic harbingers of our land; they served their major purpose long before man existed, then lingered on as noble relics to provide man with an agreeable home when he did arrive. They are mountains of ancient destiny, and to move among them is to establish contact with a notable period of our history.
They have been mentioned here to provide a counterbalance to the great things that were about to happen in the west. About seventy million years ago much of the western part of America lay beneath a considerable sea, and if this configuration had persisted, the eastern United States would have been an island much like Great Britain, but dominated by the low-lying Appalachians.
But beneath the surface of the inland sea great events portended. The combined weight of sediment and water, pressing down upon a relatively weak basin area, coincided with an upsurge of magma from the mantle. As before, these magmatic pressures from below pushed upward huge blocks of the basement, and bent the more flexible layered rocks above the basement until a massive mountain range had been erected. The range, running from northern Canada almost to Mexico, was both longer and wider than the Ancestral Rockies had ever been and placed somewhat farther east. Its major elevations stood very high, and as these areas were uplifted, the inland sea was drained off.
The mountain range was composed in part of rock that had formerly been utilized in the Ancestral Rockies—which is why we know so much about those ancient mountains we have never seen—and formed one of the world’s major structural forms, which it still does.
The Rockies are therefore very young and should never be
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