Principles of Geology Part 32

_g_, Town of Catania.

_h i_, Dotted line expressing the highest boundary along which the marine strata are occasionally seen.

_k_, Plain of Catania.

_l_, Limestone platform of Primosole of the Newer Pliocene period.

_m_, La Motta di Catania.]

The mountain is in general of a very symmetrical form, a flattened cone broken on its eastern side, by a deep valley, called the Val del Bove, or in the provincial dialect of the peasants, "Val di Bue," for here the herdsman

---- "in reducta valle mugientium Prospectat errantes greges."

Dr. Buckland was, I believe, the first English geologist who examined this valley with attention, and I am indebted to him for having described it to me, before I visited Sicily, as more worthy of attention than any single spot in that island, or perhaps in Europe.

[Ill.u.s.tration: PLATE III

VIEW LOOKING UP THE VAL DEL BOVE, ETNA]

The Val del Bove commences near the summit of Etna, and descending into the woody region, is farther continued on one side by a second and narrower valley, called the Val di Calanna. Below this another, named the Val di St. Giacomo, begins,--a long narrow ravine, which is prolonged to the neighborhood of Zaffarana (_e_, fig. 48), on the confines of the fertile region. These natural incisions into the side of the volcano are of such depth that they expose to view a great part of the structure of the entire ma.s.s, which, in the Val del Bove, is laid open to the depth of from 3000 to above 4000 feet from the summit of Etna. The geologist thus enjoys an opportunity of ascertaining how far the internal conformation of the cone corresponds with what he might have antic.i.p.ated as the result of that mode of increase which has been witnessed during the historical era.

[Ill.u.s.tration: Fig. 48.

Great valley on the east side of Etna.

_a_, Highest cone.

_b_, Montagnuola.

_c_, Head of Val del Bove.

_d_, _d_, Serre del Solfizio.

_e_, Village of Zaffarana on the lower border of the woody region.

_f_, One of the lateral cones.

_g_, Monti Rossi.]

_Description of Plate III._--The accompanying view (Pl. III.) is part of a panoramic sketch which I made in November, 1828, and may a.s.sist the reader in comprehending some topographical details to be alluded to in the sequel, although it can convey no idea of the picturesque grandeur of the scene.

The great lava-currents of 1819 and 1811 are seen pouring down from the higher parts of the valley, overrunning the forests of the great plain, and rising up in the foreground on the left with a rugged surface, on which many hillocks and depressions appear, such as often characterize a lava-current immediately after its consolidation.

The small cone, No. 7, was formed in 1811, and was still smoking when I saw it in 1828. The other small volcano to the left, from which vapor is issuing, was, I believe, one of those formed in 1819.

The following are the names of some of the other points indicated in the sketch:--

1, Montagnuola.

2, Torre del Filosofo.

3, Highest cone.

4, Lepra.

5, Finocchio.

6, Capra.

7, Cone of 1811.

8, Cima del Asino.

9, Musara.

10, Zocolaro.

11, Rocca di Calanna.

DESCRIPTION OF PLATE IV.--The second view (Pl. IV.) represents the same valley as seen from above, or looking directly down the Val del Bove, from the summit of the princ.i.p.al crater formed in 1819.[567] I am unable to point out the precise spot which this crater would occupy in the view represented in Plate III.; but I conceive that it would appear in the face of the great precipice, near which the smoke issuing from the cone No. 7 is made to terminate. There are many ledges of rock on the face of that precipice where eruptions have occurred.

The circular form of the Val del Bove is well shown in this view. (Pl.

IV.) To the right and left are the lofty precipices which form the southern and northern sides of the great valley, and which are intersected by dikes projecting in the manner afterwards to be described. In the distance appears the "fertile region" of Etna, extending like a great plain along the sea-coast.

The spots particularly referred to in the plate are the following:--

_a_, Cape Spartivento, in Italy, of which the outline is seen in the distance.

_b_, The promontory of Taormino, on the Sicilian coast.

_c_, The river Alcantra.

_d_, The small village of Riposto.

_f_, The town of Aci Reale.

_g_, Cyclopian islands, or "Faraglioni," in the Bay of Trezza.

_h_, The great harbor of Syracuse.

_k_, The Lake of Lentini.

_i_, The city of Catania, near which is marked the course of the lava which flowed from the Monti Rossi in 1669, and destroyed part of the city.

_l_, To the left of the view is the crater of 1811, which is also shown at No. 7 in Plate III.

_m_, Rock of Musara, also seen at No. 9 in Plate III.

_e_, Valley of Calanna.

The Val del Bove is of truly magnificent dimensions, a vast amphitheatre four or five miles in diameter, surrounded by nearly vertical precipices, varying from 1000 to above 3000 feet in height, the loftiest being at the upper end, and the height gradually diminis.h.i.+ng on both sides. The feature which first strikes the geologist as distinguis.h.i.+ng the boundary cliffs of this valley, is the prodigious mult.i.tude of verticle dikes which are seen in all directions traversing the volcanic beds. The circular form of this great chasm, and the occurrence of these countless dikes, amounting perhaps to several thousands in number, so forcibly recalled to my mind the phenomena of the Atrio del Cavallo, on Vesuvius, that I at first imagined that I had entered a vast crater, on a scale as far exceeding that of Somma, as Etna surpa.s.ses Vesuvius in magnitude.

But I was soon undeceived when I had attentively explored the different sides of the great amphitheatre, in order to satisfy myself whether the semicircular wall of the Val del Bove had ever formed the boundary of a crater, and whether the beds had the same quaqua-versal dip which is so beautifully exhibited in the escarpment of Somma. Had the supposed a.n.a.logy between Somma and the Val del Bove held true, the tufts and lavas at the head of the valley would have dipped to the west, those on the north side towards the north, and those on the southern side to the south. But such I did not find to be the inclination of the beds; they all dip towards the sea, or nearly east, as in the valleys of St.

Giacomo and Calanna below.