igoS.] 



THE PHYSICS OF THE EARTH. 169 



Therefore all these islands were formed by the expulsion of lava 

 from under the sea, and the subsequent sinking of the sea bottom 

 has given rise to the deep troughs now found in that part of the 

 ocean. 



In the same way there is an earthquake belt between Samoa 

 and New Zealan'd, and the sea bottom is sunk down into a deep 

 trough, parallel to a ridge on the west, on the opposite side of the 

 trench from the ocean. This ridge is a new mountain range 1,200 

 to 1,500 miles long, now forming on the west of the Pacific, just 

 as the Andes were once formed on the east. Lava is being expelled 

 from under the trench and pushed from the ocean towards the ridge 

 on the west. This is developing into a new mountain range, which 

 we shall call the Antandcs, because it is being formed opposite to 

 the Andes, on the other side of the Pacific, and in the same manner 

 as the mighty mountains in South America were in earlier geological 

 time. In the course of immense ages the Antandes will rise above 

 the water as a mighty chain on the west of the Pacific just like the 

 Andes on the east. 



These phenomena in tlie sea bottom show the real process of 

 mountain formation at various stages of its progress, and prove to 

 iis that most of the folding observed in our mountain ranges nozu 

 on land really took place in the bed of the sea, long before the zvhole 

 range zcas raised above the zcater. For this sinking and upheaval 

 of adjacent portions of the sea bottom would crumple the rocks 

 exactly as they are observed to be in all mountain ranges ; and 

 moreover the several parallel ranges so often observed would result 

 from the development of several parallel troughs, all of which are 

 eventually uplifted. It will be observed that the expulsion of lava 

 is always from the sea towards the land, and this shows that the 

 sole cause of the movement is the leakage of the ocean. It thus 

 follows that mountains, plateaus, and islands are uplifted by earth- 

 quakes depending on the leakage of the oceans, and by nothing else. 

 § 7. The Andes zvith their high Plateaus Merely a Vast Wall 

 Erected by the Pacific. — It may sound strange to say that the Cordil- 

 lera of the Andes is a vast wall erected by the Pacific Ocean along 

 its border ; but to the navigator who traverses the shore from Pan- 

 ama to Cape Horn such a description will seem most appropriate. 



