,5o8.] THE PHYSICS OF THE EARTH. 271 



373 B. C. ; Callao, 1746; Lisbon, 1755; Arica, 1868; Iquiqne, 1877; 

 Japan, 1896, were all of this class. 



20. We may pass directly from the Andes to the Himalayas, and 

 from the high plateaus of South America to those of Asia. Just 

 as the plateaus from Quito to Titicaca were formed by the expul- 

 sion of matter from under the Pacific, so also those of Tibet and 

 Iran are due mainly to the expulsion of lava from beneath the 

 Indian and Pacific Oceans. 



21. In the case of the plateau of Tibet the resulting uplift is 

 partly due to the combined action of the Pacific, which thus folded 

 the ranges to the East. With two oceans so large and deep as the 

 Indian and Pacific cooperating in this uplift, it is no wonder that 

 the maximum effect was produced and that Tibet became the highest 

 plateau in the world. 



22. The Himalayas are higher and further from the sea than the 

 Andes, but the earthquake belt at the base still persists in both cases, 

 and the configuration in regard to the sea shows that the causes at 

 work to produce these mighty uplifts were absolutely similar. And 

 if the mountains are due to the same cause, the plateaus are also. 



23. The total height of Tibet is only about one sixth or seventh 

 of the thickness of the earth's crust, and hence the uplift, great as 

 it is, is not such as would necessarily produce great volcanic out- 

 breaks at the surface. 



24. Great lava flows, however, occurred in India, and some vol- 

 canic phenomenon are known in the Himalayas, but our knowledge 

 of these mountains is not yet adequate to enable one to estimate 

 just how much volcanic activity developed there. 



25. Great lava flows are due to the rupture of the crust, by the 

 opening of a fault near the sea, not to volcanic outbreaks. These 

 flows are seen in Utah, Oregon and India, on a scale commensurate 

 with the forces which have uplifted the mountains and plateaus. 



26. One may pass directly from the mountains and plateaus of 

 South America to those of Asia, and then to those on the Paciflc 

 slope of North America, by the most gradual stages. 



27. In this transition the processes are so similar and the dif- 

 ferences so small, that it is impossible to deny that the mountains 



