Vol. 60. 1 VOLCANIC ACTION IN THE PHLEGR.EAX FIELDS. 



313 



leucotephrite. with fine crystals of leucite, which now form a thin 

 stratum in the upper part of the northern flank of the crater. 

 Up to a height of about 130 feet the crater of Avernus is filled 

 with fresh water, which one day perchance percolating below ground 

 fed the thermal springs of Tripergola, and there in September 1538 

 initiated the outburst of ^lonte Xuovo. This eruption, with its 

 ejectamenta of ash, lapilli. pumice, and lastly phonolitic scoriae, 

 forms for the present the closing chapter in the history of vul- 

 canicity in the Phlegraean Fields. With a certain amount of 

 hesitation and uncertainty I may, perhaps, venture to summarize 

 that historv in the following table : — 



Schematic Synopsis of Vuxcanicity in the Phlegraean Fields. 



^ - Si 



Eruptions of ash, lapilli, 

 pumice, and other 

 detritic materials. 



Eruptions of 



lava and scoria'. 





y: 



c • - 



■_ r 

 OQ — 



Jl — 



Monte Xuovo. 



Fond: di Baia. 



Avernus. 



Monte Grillo 

 Monte Ruscello 



Phonolitic scoria? of Monte 

 Xuovo. 



- 

 — 



• Did b •-* >F * OQ 



.2** 3 2 • .° 2 ° o 



Leucotephrite of Avernus. 



"r - d 2 w 1 4a ^» 



Fonnation of the external 

 girdle of Astroni. 



Detritic eruptions of Agnano. 



Lavas and scoriae of Monte 

 Olibano, of the internal cones 

 of Astroni, and of the craters 

 of Campana. 



Ancient lavas of -' 



the Solfatara. "| 



Scoria? of Monte Spina 2 



and trachytic mass _J- 



of Caprara. ^ j 



Outbursts of Fuorigrotta, Soccavo, 

 Pianura. Quarto, Teano, etc. 



Scoriaceous eruptions « 

 of Santa Maria del § 

 Pianto, Ponti Rossi. ^ ' 



Yellow tuff of Xisida. Posillipo. 

 Voinero, Capodimonte. the Camal- 

 doli, Gauro, Poz/.uoli, Quarto, 

 Monte di Cuma, Procida, Porto 

 Miseno, Capo Miseno, etc. 



(?) Trachytic masses 



met with in the 



various tunnels 



under the Vomero 



Hill. 



Breccias and conglomerates of the 

 Camaldoli. Cuma, Monte di Pro- 

 cida, Monte Santo, etc. 



Scoriaceous lavas and scoria? 

 of Monte di Procida, Monte 

 di Cuma. etc. 



"■^ V 



Pipernoid tuffs of the Campania. 



Piperno. Trachyte of Cuma. 



Q.J.G.S. No. 23!'. 



