Show M MOUNTAINS 0 U N S. S An Interesting Description of How flow They Are Made Mado Foremost in their geographic importance importance im im- and andin andia in the tho intricacy and significance sig tug ance of their geological construction construction construe construe- tion arid and origin aro aro the tho mountain belts which which consist consist of folded rock forma forma- Tho The strata forming the upper part of the earths earth's crust nr are bent up and down dO in long nearly straight or curving wave-like wave ridges or troughs and where their disturbance was greatest the tho successive ridged folds are closely pressed together The waves of tho the rock structure are aro then pulled to such steepness that the their sides become parallel with each other and the entire fold is driven forward into an incline position The order of the strata on the lower side of the oppressed told fold is thus inverted the ori originally highest and last formed deposits there Ho lie beneath older beds in an overturned overturn d series Sub aerial erosion then wears Vears down the undulations and the crest crests crests' of the cl closely sely fo folded strata often tl them em of off until a long section crossing mountain ranges passed from flom older to newer beds and onward from Irons newer to older in several alternations having having haying hav hay ing throughout hout the tho whole a nearly constant nt deep dip Owing to the of hard and enduring enduring- sandstone gneiss and other rock formation with more easily eroded limestone incoherent sandstones or the tho erosion comm commonly produces n a ne topography making hollows and long valleys where the more beds bed have been removed and and mountain ranges of the harder rocks More than this When erosion has been continued through long periods period it tends toward the ultimate result of or removing the upward curved or anti anti- portions of the great folds and sparing the originally lo lower er downward downward down down- ward curved d or br 01 portions until the valleys take the places which were originally occupied by the highest highest highest high high- est upheavals while the ori original troughs where tho rocks were rocks were most compacted by bv pressure remain now as s the principal mountain rid ridges es Under denudation the folded mountainous mountainous moun moun- belt fulfils the prophecy Ey Every ry vall valley valley- y s shall ll bo be exalted and ana every mountain and hill kill shall be low by Popular Science Monthly |