28 LIFE: ITS NATURE AND ORIGIN 



While some helium is probably lost, determinations on rocks 

 preceding the Cambrian indicate an age for the solid earth of 

 about 1,830 million years, and this checks fairly well with a "lead" 

 age calculation as determined on uraninite found in Russia. 23 



Volcanism and Nuclear Energy 



At Paricutin (Mexico) we have been witnessing the birth and 

 formation of a volcano in what had been flat farming country. 

 After three years the cone has reached a height of over three thou- 

 sand feet, and in the fall of 1946 two new craters were reported 

 emitting floods of lava. Professor Wilbur A. Nelson (Virginia) 

 estimated that during the Cretaceous period a Tennessee volcano 

 spat up over fifty cubic miles of material, part of which settled 

 down to form beds of bentonite clay extending nearly 500 miles 

 north and south, and nearly 400 miles east and west. But the 

 Paricutin manifestations are trivial compared with what happened 

 at Krakatoa within the memory of many now living. 



Krakatoa is a small volcanic island in Sunda Strait between Java 

 and Sumatra. A prehistoric explosion had blown away some old 

 volcano, leaving an outer ring of islands outlining its huge crater. 

 Later, the main cone, built up by subsequent eruptions, rose over 

 2,600 feet above sea level. About 1877 earthquakes began, and 

 on Aug. 26th, 1883, came a series of gigantic explosions lasting 

 three days, which blew away the entire north and lower portion 

 of the island, leaving a bare vertical cliff which revealed the 

 interior of the volcanic cone Rakata. It replaced heights of from 

 300 to 1,400 feet with submarine cavities 1,000 feet deep in some 

 places. The huge amount of matter cast out to an estimated 

 height of 17 miles gave off a colloidally dispersed dust cloud, or 

 aerosol, which travelled to Europe, Asia, Africa, North and South 

 America, and throughout Australasia. This cloud reached north- 

 ern Scandanavia and the Cape of Good Hope, and caused brilliant 

 sunsets for several years. Pumice floated for hundreds of miles, 

 and ocean waves, some 50 feet high, reached Cape Horn (nearly 

 8,000 miles) and perhaps the English Channel (11,000 miles). 

 More than 36,000 people were killed. The sound of the explo- 

 sions carried nearly 3,000 miles, being heard in the Philippines, 

 Ceylon, and in South and West Australia — by far the greatest dis- 

 tance sound has been known to travel. On the morning of 

 Aug. 27th, a most powerful explosion originated an atmospheric 

 wave which, being reflected or reproduced at the antipodes to 



