504 WITHIN THE EARTH'S CRUST 



can readily be studied. The following descriptions of some 

 well-known typical volcanoes show some of the results of 

 subsurface activity. 



Monte Nuovo. In 1538, on the shore of the Bay of 

 Naples near Baise, that once famous resort of the Roman 

 nobles, after a period of severe earthquake shocks there 

 suddenly occurred a tremendous eruption. From within 

 the earth emerged a mass of molten material blown into 

 fragments by the explosion of the included gases. Within 

 a few days there was formed Monte Nuovo, a hill 440 feet 

 high and half a mile in diameter, having in the top a cup- 

 shaped depression or crater over 400 feet deep. 



So great was the explosive force of this eruption that 

 none of the ejected material was poured out in the form of a 

 liquid. The whole hill is made up of dust, small stones, and 

 porous blocks of rock which resemble the slag of a blast 

 furnace. The small fragments in such eruptions are called 

 ash or cinders. In a week the eruption was over, and noth- 

 ing of the kind has since occurred in the region. 



When visited by the writer a few years ago, the bottom 

 of the crater was a level field planted to corn. The whole 

 process of formation of this volcanic cone was observed and 

 recorded by residents of the region. Other similar eruptions 

 have been observed, but perhaps this is the best known. 



Vesuvius. When the Roman nobles were building 

 their magnificent villas and baths along the shore of the 

 Bay of Naples, the scenic beauty of the region was greatly 

 increased by a mountain in the shape of a truncated cone, 

 which rose from the plain a few miles back from the shore. 

 Its sides, nearly to the summit, were covered with beautiful 

 fields. 



