RISE OF MOLTEN ROCK TO THE EARTH'S SURFACE 97 



illustration of this largest and most interesting of new-born vol- 

 canoes. As in the case of Jorullo, the eruption began with the 

 formation of a fissure in a 

 level plain, some 400 yards 

 distant from the town of 

 Catarman (Fig. 88). The 

 eruption continued for four 

 years, at the end of which 



time the height of the SUm- FlG - 88. View of the new Camiguin volcano 



., , . , i i ,i from the sea. It was formed in 1871 over 



mit Was estimated by the a nearly level plain. The town of Catarman 



Challenger expedition to be 



^-cC^~.; : -~ 



appears at the right near the shore (after an 

 unpublished photograph by Professor Dean 

 C. Worcester). 



1900 feet. At the time of 



the first ascent in 1905, 



the height was determined by aneroid as 1750 feet, with sharp 



rock pinnacles projecting some 50 or 75 feet higher. 



Active and extinct volcanoes. The terms " active " and 

 " extinct " have come into more or less common use to describe 

 respectively those volcanoes which show signs of eruptive activity, 

 and those which are not at the time active. The term " dormant " 

 is applied to volcanoes recently active and supposed to be in a 

 doubtfully extinct condition. From a well-known volcano in 

 the vicinity of Naples, volcanoes which no longer erupt lava or 

 cinder, but show gaseous emanations (fumeroles) are said to be in 

 the solfatara condition, or to show solfataric activity. 



Experience shows that the term " extinct," while useful, must 

 always be interpreted to mean apparently extinct. This may be 

 illustrated by the history of Mount Vesuvius, which before the 

 Christian era was forested in the crater and showed no signs of 

 activity ; and in fact it is known that for several centuries no erup- 

 tion of the volcano had taken place. Following a premonitory 

 earthquake felt in the year 63, the mountain burst out in grand 

 explosive eruption in 79 A.D. This eruption profoundly altered 

 the aspect of the mountain and buried the cities of Pompeii, Stabeii, 

 and Herculaneum from sight. Once more, this time during the 

 middle ages, for nearly five centuries (1139 to 1631) there was 

 complete inactivity, if we except a light ash eruption in the year 

 1500. During this period of rest the crater was again forested, 

 but the repose was suddenly terminated by one of the grandest 

 eruptions in the mountain's history. 



