CHAPTER II 



SUBMARINE MOUNTAINS 



Introduction 



The traveler at sea, whether lighthearted tourist or seasoned 

 sailor of the crew, knows the thrill of the landfall, and the 

 emotion is perhaps most lively when one of the deep-sea islands 

 looms out of the mist. Sharing this human feeling, com- 

 pounded of curiosity and the nostalgia of a land animal, the 

 geologist on board looks at the growing profile with special 

 excitement. More than others he senses challenging mystery. 

 He has the divine stimulus of wonder. How did this island 

 originate? Why does it lift its head above a sea floor which, 

 through hundreds or thousands of miles of traverse, has been 

 10,000 to 20,000 feet below the ship ? What can this island add 

 to knowledge of the earth's crust as a whole ? The first chapter 

 sketched the results of instrumental study of the general floor 

 of the ocean. We shall now seek further light among the 

 thalassic islands and the related shoals far out from the con- 

 tinents. 



Hundreds of invisible shoals, like the island masses, begin 

 their rise above the flat plain of bottom ooze and mud, at 

 depths ranging from two to four miles below sealevel. Both 

 shoal and island are therefore lofty mountain masses. Wherever 

 visible, the lava is basalt or, in far smaller proportion, a chem- 

 ical derivative of basaltic liquid, either pure or contaminated 

 by absorbed crust-rock or water. We recall that basalt is the 



