Page:Popular Science Monthly Volume 71.djvu/189

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SOME LITTLE KNOWN MEXICAN VOLCANOES
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perature of about 130 degrees Fahrenheit and sulphur dioxide are issuing from numerous fumaroles, some of which are lined with sulphur crystals. The crater is comparatively small, having a diameter of little over half a mile.

Recent Eruptions.—In 1877, 1884 and 1885 minor eruptions occurred. The last eruption of the volcano commenced in the month of February, 1903, and practically ceased in May of the same year. Since that time the only evidences of activity are the fumaroles from which issue large quantities of steam and other gases. During this eruption

Fig. 6. Flank of Toluca.

(1903) a lava stream flowed down the slope of the volcano in a northwest direction, but barely reached the foot of the volcano (see diagram), where it dammed a small stream, thus forming a shallow pond.

The accompanying diagrammatic cross-section of the volcano shows the relations of the secondary cone to the main cone, the position of the lava flow of 1869, the edge of this flow (a), the rim of the old crater (b), the lava flow of 1903, and the position and relative heights of Colima and the Nevado of Colima (which may have been the remnant of the rim of a great volcano long since destroyed). In the construction of this diagram, no attempt was made to draw the distances or heights to scale, but to bring out the salient points as clearly as possible,

Volcano Toluca

In the midst of the valley of Toluca, the Nevado of Toluca (Xinantecatl) towers almost 0,000 feet above the level of the plain and 14,833