The Sierra Madre

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They came right up out of the earth. In Love’s phrase, they simply “poached out.” Basins flexed between them, filling as they downwarped-folding, too, especially at their edges. These mountains moved, but not much-five miles here, eight miles there. They moved in highly miscellaneous and ultimately perplexing directions. The Wind River Range crept southwest, about five inches every ten years for a million years. The Bighorns split. One part went south, the other east. Similarly, the Beartooths went east and southwest. The Medicine Bows moved east. The Washakies west. The Uintas north. All distances were sh01t, because the mountains were essentially rooted. The Sierra Madre did not move at all. The spines of the ranges trended in as many directions as a weathervane. The Laramie Range trended north-south. The Wind Rivers and Bighorns northwest-southeast. The spectacularly anomalous Uintas, lining themselves up at right angles to the axis of the Western cordillera, ran east-west, and so did the Owl Creeks. All these mountain ranges zakelijke energie vergelijken were coming up out of the craton-heartland of the continent, the Stable Interior Craton. It was as if mountains had appeared in Ohio, inboard of the Appalachian thrust sheets, like a family of hogs waking up beneath a large blanket. An authentic enigma on a grand scale, this was one of the oddest occurrences in the tectonic history of the world. It would probe anybody’s theories. It happened rapidly. As David Love at one point remarked about the Medicine Bow Mountains, “It didn’t take very long for those mountains to come up, to be deroofed, and to be thrust eastward. Then the motion stopped. That happened in maybe ten million years, and to a geologist that’s really fast.” Twenty thousand feet of rock was deroofed from the rising mountains. The entire stratigraphy from the zakelijke energie Cretaceous down to the Precambrian was broken to bits and sent off to Natchez, as the mountains were denuded to their crystalline and metamorphic cores. In half a billion years of history, this was the great event. In the words of the Geologic Atlas of the Rocky Mountain Region, it was “tectonically unique in the Western Hemisphere and, therefore, it seems to require a somewhat unusual if not unique tectonic interpretation.” The foreland ranges, as the mountains east of the overthrust are called (the Wind Rivers, Uintas, Bighorns, Medicine Bows, Laramie Range, and so forth), came into the world with their own odd syncopation, albeit the general chronology went from west to east and the Laramie Range was among the last to rise. “The mountains were restless,” Love was saying now.

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