8 THE ROMAN COMAGMATIC REGION. 
edge of the district; Sessa Aurunca, similarly placed on the southwest; and Conca, 
on the northern outer slope. 
Campanian District. 
This district may be conveniently divided into three subdistricts the Vesbian,* 
which consists of the Vesbian Volcano, a convenient appellation for the mass of 
Mount Vesuvius and the encircling Monte Somma; the Phlegrean, embracing the 
volcanoes of the Phlegrean Fields; and the Ischian, consisting of the island of Ischia. 
The Vesbian Volcano is so well known and has been described so often that 
little need be said of it here. It consists of the older ring of Somma, which forms 
a half-circle open to the south, with a maximum elevation of 1,137 meters. Inside 
this, and slightly eccentric to the south, rises the cone of Vesuvius to a height of 
about 1,300 meters, the product of the long series of eruptions since 79 A. D. The 
valley between the Somma ring and the cone of Vesuvius is called the Atrio del 
Cavallo. 
As is well known, the Vesbian Volcano is a typical strato- volcano, composed of 
lava flows and interbedded tuffs, which are deeply scored by radial erosion valleys 
on the outer slopes of Somma. The total area covered by the eruptive products of 
the volcano, exclusive of the thin beds of tuff which extend to considerable distances 
around it, may be estimated at 300 square kilometers. 
The Phlegrean Fields are only less well known than Vesuvius, and consist of 
numerous small volcanoes, of which Giinther enumerates 26, arranged in 6 groups. 
The most important ones are: Pianura and Soccavo, which are among the earliest; 
Astroni, Olibano, Solfatara, Campiglione, Cuma, Averno, Monte Nuovo (which is 
the latest and was formed in 1538), Monte di Procida, Capo Miseno, and the small 
islands of Nisida, Procida, and Vivara. None of these volcanoes is of very large 
size or great altitude, and they have ejected very small amounts of solid lava, 
the material for the most part being tuffs. The total area of the Phlegrean Fields 
has been estimated at about 130 square kilometers. 
The island of Ischia, with an area of 46.5 square kilometers, is somewhat 
pyramidal in form, rising up to the summit of Monte Epomeo (792 meters), which is 
the ruin of the original large volcano, of the crater of which traces remain at Fon- 
tana. In large part the island, and especially the main mass of the Epomeo Vol- 
cano, is built up of tuffs, but lava flows are also to be found. Flanking the Epomeo 
Volcano, especially on the east and north, are several parasitic cones, of which there 
may be mentioned Monte Campagnano on the southeast, Castello d'Ischia on the 
east coast, the lava flow of L'Arso (1302 A. D.), which, issuing from Le Cremate 
about half-way up the east slope of Epomeo, reaches the sea at the northeastern 
corner of the island, and Lago di Bagno, Montagnone, Monte Rotaro, and Monte 
Tabor, which lie along the north coast. The extreme northwest corner of the island 
is occupied by the mass of Marecocco and Zale, which may belong to the eruption 
of 470 B. c. 
* From an ancient name of Mount Vesuvius. 
