210 - GEOGNOSY AND GEOLOGY. 
level, as can be satisfactorily shown in some cases, might have been 
so different from what it is now, as even to have washed the very 
bases of the cones. Pl. 47, fig. 1, presents a comprehensive view ofthe 
volcanic regions of the globe; fig. 2 is a chart of European volcanoes, fig. 
3, of those of lower Italy, all after Berghaus. On the latter, the earthquake 
region of Calabria and Sicily is indicated by the dark lines; that of Naples 
by a dotted outline. A fuller explanation of these charts will be found 
under the head of Physical Geography. 
The shape of volcanoes is in general that of a more or less perfect, acute, 
or truncated cone. The ejected matters are heaped up around the mouth 
or crater. One of the most beautiful cones of this character is the Pie de 
Teyde on Teneriffe, as also Cotopaxi in the Andes chain. ‘The height of 
volcanoes varies considerably, sometimes not reaching to the level of the sea, 
and at others extending into the higher regions of the atmosphere. Thus 
Stromboli, on the Lipari Islands, attains a height of 2,687 feet; Etna, of 
10,814; the Peak of Teneriffe, 12,172; Mauna Roa, 13,760, and Mauna 
Koa, 13,953 (Sandwich Islands); Tunguragua in Quito, 16,424; Popo- 
catepetl, 17,717, and Orizaba, 17,374 (Mexico); Cotopaxi, 18,890; 
Antisana, 19,150; Pinchincha, 15,940; Hecla, 3,324; Vesuvius, 3,978; 
Mount St. Elias, in North Western America, 16,775; Awatsha, in 
Kamschatka, 9,600. These heights are all above the level of the sea. The 
absolute height of the scoria about volcanoes naturally depends upon the 
number of eruptions. In Vesuvius they occupy 1, in Pinchincha ;;, and in 
the Peak of Teneriffe 3, of the entire cone. This part of the volcano, as 
forming the apex of the whole, naturally presents very steep sides of a mean 
inclination of 33° to 40°. The steepest parts of Vesuvius, of Jorullo, and 
of the Peak of Teneriffe, have an inclination of 40° to 42°. 
The summit of the scoria cone is generally provided with a funnel- 
formed aperture, the crater. It is erroneous to suppose that the largest 
cones must necessarily have the largest craters; in fact, it would be more 
generally correct to say that the larger the cone the smaller the crater. 
The crater, generally circular, is of various diameters; that of Stromboli 
measures 50 feet, that of Vesuvius 1500 and over, of Etna 1250. The 
nearly elliptical crater of the Peak of Teneriffe has diameters of 200 and 
300 feet, that of Popocatepetl 5000 and 4000. The largest known crater is 
that of Mauna Roa in the island of Hawaii; this is three and a half miles 
long, two and a half wide, and a thousand feet deep, large enough, in the 
language of Captain Wilkes, to accommodate the entire city of New York, 
leaving still an abundance of room. 
The edge of the crater may also vary in character; it is generally, 
however, elevated like a wall, and descending nearly vertically towards the 
mouth (pl. 50, fig. '7, interior of the crater of Etna). It is often intersected 
by deep fissures, through which access may be had to the mouth. The 
depth of the crater of the Peak of Teneriffe amounts to 110-115 feet, 
that of Pinchincha to 1800, and that of Popocatepetl to 800-1000 feet. 
The bottom of the crater is either simple or provided with various small 
cones of eruption, of which a greater or less number are in active operation. 
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