382 E. C. ANDREWS THE HYPOTHESIS OF MOUNTAIN FORMATION 



It forms one of a series of four related papers. One of these is included 

 in the Broken Hill Eeport itself.- The others deal with the origin of 

 ''Coral reefs'' ^ and the "Distribution of ore dej^osits in Australia/"" re- 

 spectively. 



Distribution and Arrangement of the present Mountains of 



THE Earth 



In the present jDaper brief reference is made only to a few salient facts 

 concerning the mountains which are related to the Pacific Ocean and to 

 the ancient resrions of Tethvs. 



The mountains of Eurasia, Xorth America, South America, and Aus- 

 tralia are arranged in rings or belts, which rise j^rogressively in height 

 in proportion to the distance traversed from the continental nuclei toward 

 the equatorial or Tethyan region on the one hand and the Pacific Ocean 

 on the other. These heights are referred to the nearest sea-floor or "ocean 

 deep"' as base. 



In Eurasia the outer rings of the mountains are the subparallel belts 

 of the island arcs of the Pacific and Malaysia, together with the s^Titactic 

 arcs of the Himalaya, the Alps, and related ranges, such as the Pyrenees 

 and the Elburz. 



In Australia the mountains pass from the southwestern nucleus in 

 broad and compound undulations, by way of the eastern Australian region 

 to Malaysia and the island arcs of the southwestern Pacific. 



In America the mountains pass toward the Pacific in the main from 

 the continental nuclei in a complicated series of syntactic arcs separated 

 by tectonic valleys. These arcs include the Rockies and its subordinate 

 divisions, such as the Selkirks, the Cascades, the Sierra, the Coast ranges, 

 the Andes, and related ranges. 



These plateau strips of America, together with their separating valleys, 

 are the eastern homologues of the Japanese, Caroline, Solomon, Tongan, 

 Samoan, Fijian, Society, and other island arcs of the western Pacific. 



This statement needs some slight modification, inasmuch as the Amer- 

 ican mountains have l)een controlled in some measure l)y the suboceanic 

 mass of the Atlantic region. Recurrence is made to this point below. 



The Indian Peninsula is related to the Indian Ocean in a manner 

 similar to that of northern America with the Pacific. 



Africa shows a distinct division into two parts, namely, a northern one, 

 which is controlled by the Tethyan area, and a southern one, which shows 



- E. C. Andrews : Geology of Broken Hill. Memoirs No. 8. Geological Society of New- 

 South Wales, in-2-2. 



3 E. C. Andrews : Presidential address. Roy. Society of New South Wales, 1922. 



