MONTE NUOVO 441 



solid part of the earth could not be more than 40 or 50 miles 

 thick, as the interior heat would melt rocks under ordinary 

 pressure. But the earth is too rigid for its interior to be 

 otherwise than solid. So great is the pressure to which it 

 is subjected that probably none of the material deep down 

 in the interior of the earth is in a molten condition. 



If the pressure near the surface should be decreased, 

 or if the normal amount of heat at any place should be 

 increased, the material might become fused, and under 

 certain conditions might find its way to the surface. We 

 know that heated material from below does rise toward the 

 surface and intrude itself into the surface rocks and in 

 some places pour forth over the surface. 



What causes the uprising and outpouring of this molten 

 material from below the surface of the earth, and how and 

 why it reaches the surface are questions which as yet are 

 unanswerable. But as soon as this igneous material comes 

 within the range of observation, its properties and actions 

 can readily be studied. The following descriptions of some 

 well-known typical volcanoes show some of the results of 

 subsurface activity. 



210. 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 



