Thirty million years

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During those thirty million years after things went blah, the Rockies were quietly buried ever deeper in their own debris-and, not so peacefully, in materials oozing overland or falling from the sky. Much came in on the wind from remote explosive volcanoesstratovolcanoes of huge size in Idal10, Oregon, Nevada. “And maybe Arizona and California, for all we know,” Love said. “Clinical details are still inadequate. By the end of the Eocene, the Washakie and Owl Creek Mountains were so deeply buried that the Wind River and Bighorn Basins had coalesced above them. At the end of the Oligocene, only a thousand to four thousand feet of tl1e highest mountains protruded above the aggradational plain. Streams were slow and zakelijke energie vergelijken sluggish and so choked with ash they were unable to erode.” Rhinoceroses lived through those changes, and ancestral deer and antelope, and little horses with three toes. As altitude and aridity increased, a subtropical world of figs, magnolias, and breadfruit cooled into forests of maple, oak, and beech. Altitude alone could not account for the increasing coolness. It foreshadowed the coming ice. The burial of the mountains continued far into the Miocene, with-as Love described it-“surprising thicknesses of sandstone and tuffaceous debris.” Volcanic sands, from Yellowstone and from elsewhere to the west, were spread by the wind, and in places formed giant dunes. Two thousand feet of sand accumulated in central Wyoming. Nineteen thousand-the thickest Miocene deposit in America-went into the sinking Jackson Hole. From the Wind River Mountains southward to Colorado and eastward to Nebraska, the plain was unbroken except for theĀ zakelijke energie tops of the highest peaks. Rivers were several thousand feet higher than they are now. The ranges, buried almost to their summits, were separated by hundreds of miles of essentially flat terrain.

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