As the Rockies were being created, the climate of the continent’s interior began to change. The long reign of the dinosaurs that had presided over a stable, tropical landscape was coming to an end. The climate was gradually becoming cooler and drier. Doubtless the immense volumes of volcanic ash ejected into the atmosphere prevented a 세종오피 percentage of solar heat from reaching the Earth. Certainly the rise of the Rocky Mountains to the west influenced the old weather patterns. As the mountain blocks rose higher, they intercepted the warm, moist winds that blew inland from the Pacific. With the air masses rising ever higher, more and more of the moisture that had watered the extensive inland Cretaceous forests and swamplands was prevented from reaching what we know today as the Great Plains.

Steadily the forests retreated eastward as the “rain shadow” cast by the mountains extended eastward, shutting off the moist, warm Pacific winds. No longer moderated by these winds, the mid-continent was increasingly opened to seasonal invasions of northern arctic air. Newer ecosystems, such as deserts and grasslands, slowly evolved to replace the lush forests and swamps that had for so long sustained the dinosaurs. 26 Just as drought, fire, and temperature extremes began to alter the old order in the plant kingdom, so did the more adaptable mammals and birds begin to replace reptiles as dominant animal forms.But not all the magma that welled upward during this restless period reached the Earth’s surface. Extensive masses were trapped far below the surface, where they gradually cooled and congealed. The Missouri Buttes and Devils Tower, however, are believed to be necks of extinct volcanoes. Geologic evidence indicates the Missouri 시흥오피 Buttes formed first in two separate eruptions. The magma hardened, plugging the plumbing underneath. A third eruption to the southeast resulted in Devils Tower.

During the ensuing tens of millions of years, the gradual erosion of the overlying rock strata revealed these intruded plugs of volcanic rock. Since this dense, hard igneous rock resists erosion much better than the surrounding sedimentary rock, these formations will continue to stand out as features.

That ancient land of sedimentary rock through which the molten 구리오피 mass of Devils Tower penetrated may at one time have been as high as the golden eagle I now see drifting high above the Tower. Circling slowly in its morning hunt, the eagle spirals upward on the currents of warm air rising off the sun-heated rock. Perhaps it now soars at the elevation of the land long ago when the heavy, ringing-hard rock of Devils Tower oozed like paste far below the surface.

Today the top of the Tower is 386 meters (1,267 feet) above the Belle Fourche River. If that warm, Cretaceous landscape rested 600 meters (2,000 feet) above the present summit of the Tower, then more than 900 vertical meters 김포오피 (3,000 feet) of sedimentary rock has been pared away in the last 60 million years.

The relentless physical agents of erosion—running water, wind, and frost action—together with chemical breakdown of rock particles, continue to alter the landform. Given enough time, even the very hard rock of the Tower itself will waste away.

Sixty million years ago, when dinosaurs Triceratops and Tyrannosaurus Rex duelled beside the lush river banks of the predecessor of the Belle Fourche, the ancestor of the golden eagle was flying overhead. Millions of years hence, a descendant of the eagle might soar above this same Wyoming landscape. Missing will be the unique shaft of fluted rock we call Devils Tower. And what of the men, who for a mere eyeblink of time, hunted in its shadow or came to wonder at its somber countenance in the morning sun?