384 E. C. ANDREWS THE HYPOTHESIS OF MOUNTAIN FORMATION 



There are two related, but independent, controls for these Eurasian 

 ranges, namely, the Pacific and the Equatorial (Tethyan or Southern). 

 The result is an interference of controls which has given rise to a great 

 mountain system like a vertebral column from the Stanovoi in the north- 

 east of Asia to the great Pamir Plateau in the south. The knots or 

 vertebrae form mountain ranges which increase in grandeur, as do also 

 their attached ribs or ranges of varied lengths, as they are traced pro- 

 gressively southward through the festoons of the Stanovoi, Yablonoi, 

 Saigon, Altai, Alai, Tian Shan, Kuen Lun, Hindu Kush, Karakoram, 

 and Himalaya. 



Each of these represents a compound earth wave or undulation, 

 whether of interference or of outward and relatively unimpeded pulsa- 

 tion. The Pamir and the Himalaya are types of interference and of out- 

 ward pulsation respectively. 



Each of these units, such as the Himalaya, with the great Tibetan 

 Plateau, is ornamented with longitudinal ridges or plateaus of tectonic 

 origin arranged parallel to the main trend of the range itself. As the 

 continental margin or ocean is approached, the mountains open in swing- 

 ing nature to assume parallelism with the coast. Examples are the 

 Stanovoi, Manchurian, Chinese, Burmese, Himalayan, Persian, and 

 mountains of other Asiatic provinces. So also the Kurile, Aleutian, 

 Japanese, Philippine, Malaysian, and other island arcs represent the 

 Pacific Ocean analogues of the Himalaya or Tethyan type. 



These land crests are all separated either by land troughs, sea basins, 

 or by ocean trenches. 



With progressive passage outward from the nuclei, it may be seen that 

 the complex rings of plateaus become narrower, higher, and more discon- 

 tinuous as land surfaces considered as units. 



This is a generalization for Asia which it might be advisable to bear 

 in mind in connection with the distribution of the mountains of other 

 continents. 



Age of the existing Mountains 



Every important mountain range or arc, together with its associated 

 land trough, is a complete earth wave and may be considered as composed 

 of a main structure which possesses pressure ridges, or subsidiary ranges, 

 both attached to it and arranged subparallel to it, but lying at a greater 

 radial distance from the continental nucleus tlian the main ranges. 



Examples are (1) the main, lesser, and sub Himalayas; (2) western 

 Fiji, the zone of volcanic islands, the raised coral limestone islands, with 

 volcanic or sedimentarv nuclei, the eastern atolls. 



