Sierras

• Sierras

60:3.3This pe­riod thus be­comes the mod­ern moun­tain-build­ing stage of ge­o­logic his­tory. Prior to this time there were few moun­tain peaks, merely el­e­vated land ridges of great width. Now the Pa­cific coast range was be­gin­ning to el­e­vate, but it was lo­cated seven hun­dred miles west of the pres­ent shore line. The Sier­ras were be­gin­ning to form, their gold-bear­ing quartz strata be­ing the prod­uct of lava flows of this epoch. In the east­ern part of North Amer­ica, At­lantic sea pres­sure was also work­ing to cause land el­e­va­tion.

• Sierras

61:3.325,000,000 years ago there was a slight land sub­mer­gence fol­low­ing the long epoch of land el­e­va­tion. The Rocky Moun­tain re­gion re­mained highly el­e­vated so that the de­po­si­tion of ero­sion ma­te­rial con­tin­ued through­out the low­lands to the east. The Sier­ras were well re-el­e­vated; in fact, they have been ris­ing ever since. The great four-mile ver­ti­cal fault in the Cal­i­for­nia re­gion dates from this time.

• Sierras

61:4.210,000,000 years ago be­gan an age of wide­spread lo­cal land de­posits on the low­lands of the con­ti­nents, but most of these sed­i­men­ta­tions were later re­moved. Much of Eu­rope, at this time, was still un­der wa­ter, in­clud­ing parts of Eng­land, Bel­gium, and France, and the Med­i­ter­ra­nean Sea cov­ered much of north­ern Africa. In North Amer­ica ex­ten­sive de­po­si­tions were made at the moun­tain bases, in lakes, and in the great land basins. These de­posits av­er­age only about two hun­dred feet, are more or less col­ored, and fos­sils are rare. Two great fresh-wa­ter lakes ex­isted in west­ern North Amer­ica. The Sier­ras were el­e­vat­ing; Shasta, Hood, and Rainier were be­gin­ning their moun­tain ca­reers. But it was not un­til the sub­se­quent ice age that North Amer­ica be­gan its creep to­ward the At­lantic de­pres­sion.