60:4.2 (691.5) This period also witnesses the end of the continental drift and the building of the modern mountains of Urantia. But the pressure of the continental masses and the thwarted momentum of their agelong drift are not the exclusive influences in mountain building. The chief and underlying factor in determining the location of a mountain range is the pre-existent lowland, or trough, which has become filled up with the comparatively lighter deposits of the land erosion and marine drifts of the preceding ages. These lighter areas of land are sometimes 15,000 to 20,000 feet thick; therefore, when the crust is subjected to pressure from any cause, these lighter areas are the first to crumple up, fold, and rise upward to afford compensatory adjustment for the contending and conflicting forces and pressures at work in the earth’s crust or underneath the crust. Sometimes these upthrusts of land occur without folding. But in connection with the rise of the Rocky Mountains, great folding and tilting occurred, coupled with enormous overthrusts of the various layers, both underground and at the surface.
60:4.3 (692.1) The oldest mountains of the world are located in Asia, Greenland, and northern Europe among those of the older east-west systems. The mid-age mountains are in the circumpacific group and in the second European east-west system, which was born at about the same time. This gigantic uprising is almost ten thousand miles long, extending from Europe over into the West Indies land elevations. The youngest mountains are in the Rocky Mountain system, where, for ages, land elevations had occurred only to be successively covered by the sea, though some of the higher lands remained as islands. Subsequent to the formation of the mid-age mountains, a real mountain highland was elevated which was destined, subsequently, to be carved into the present Rocky Mountains by the combined artistry of nature’s elements.
60:4.4 (692.2) The present North American Rocky Mountain region is not the original elevation of land; that elevation had been long since leveled by erosion and then re-elevated. The present front range of mountains is what is left of the remains of the original range which was re-elevated. Pikes Peak and Longs Peak are outstanding examples of this mountain activity, extending over two or more generations of mountain lives. These two peaks held their heads above water during several of the preceding inundations.
60:4.5 (692.3) Biologically as well as geologically this was an eventful and active age on land and under water. Sea urchins increased while corals and crinoids decreased. The ammonites, of preponderant influence during a previous age, also rapidly declined. On land the fern forests were largely replaced by pine and other modern trees, including the gigantic redwoods. By the end of this period, while the placental mammal has not yet evolved, the biologic stage is fully set for the appearance, in a subsequent age, of the early ancestors of the future mammalian types.
60:4.6 (692.4) And thus ends a long era of world evolution, extending from the early appearance of land life down to the more recent times of the immediate ancestors of the human species and its collateral branches. This, the
60:4.7 (692.5) [Presented by a Life Carrier of Nebadon assigned to Satania and now functioning on Urantia.]
The Urantia Book
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Paper 61The Mammalian Era on Urantia
61:0.1 (693.1) THE era of mammals extends from the times of the origin of placental mammals to the end of the ice age, covering a little less than fifty million years.
61:0.2 (693.2) During this Cenozoic age the world’s landscape presented an attractive appearance—rolling hills, broad valleys, wide rivers, and great forests. Twice during this sector of time the Panama isthmus went up and down; three times the Bering Strait land bridge did the same. The animal types were both many and varied. The trees swarmed with birds, and the whole world was an animal paradise, notwithstanding the incessant struggle of the evolving animal species for supremacy.
61:0.3 (693.3) The accumulated deposits of the five periods of this fifty-million-year era contain the fossil records of the successive mammalian dynasties and lead right up through the times of the actual appearance of man himself. 1. The New Continental Land Stage
The Age of Early Mammals
