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Show 76 NEWER PLIOCENE PERIOD. [Ch. VII. and before him, to the north, the cone of Etnn (see di~gram No. 11 ). At the base of the cone he beholds a l~w hne. of hills e, e (No. 11), formed of clays and mads, .ass~c1ated With yellowish sand, similar to the formation provmc1ally termed 'Creta ' in various parts of Sicily. Thi~ marine formation, which is composed partly of volcanic and partly of sedimentary rocks, is seen to underlie the modern lavas of Etna. rr0 what extent it forms the base of the mountain cannot be observed, for want of sections of the lower part of the cone, but the marine sub-Etnean beds are not observed to rise to a greater elevation than eight hundred, or, at the utmost, one thousand feet above the level of the sea. We should remind the reader, that the annexed drawing is not a section, but an outline view of Etna, as seen from Primosole, so that the proportional height of the volcanic cone, which is, in reality, ten times greater than that of ~he hills of' Creta,' at its base, is not represented, the summit of the cone being ten or twelve miles more distant from the plain of Catania, than Licodia. Connexion of the sub-Etnean strata with those of the Val di Noto.-Thesemarine strata are found both on the southern and eastern foot of Etna, and it is impossible not to infer that they belong to the inferior argillaceous series of the Val di Noto, which they resemble both in mineral and organic characters. In one locality they appear on the opposite sides of the Valley of the Simeto, covered on the north by the lavas of Etna, and on the south by the Val di Noto limestone. Val di Noto. No. 12. Etna. Section from Palet·nu by Lago eli Naft'ia to Palagon'ia. a, Plain of the Simeto. b, Base of the cone of Etna, composed of modem lavns. c, Limestone of the Val di Nolo. d, Clay, sand, and associated submarine vol· canic rocks. If in the country adjacent to the Lago di Naftia, through Ch. VII.] SUB-ETNEAN FORMATIONS, 77 which the annexed section is drawn, and in several other districts where the ' creta' prevails, together with associated sub~ marine lavas, and where there is no limestone capping, a volcano should now burst forth, and give rise to a great cone, the position of such a cone would exactly correspond to that of the modern Etna, with relation to the rocks on which it rests. Southern base of Etna.-The marine strata of clay and sand already alluded to, alternate in thin layers at the southern base of Etna, sometimes attaining a thickness of three hundred feet or more,, without.any intermixture of volcanic matter. Crystals' of selemte are dtspersed through the clay, accompanied by a few shells, almost entirely of recent Mediterranean species. This formation of blue marl and yellow sand greatly resembles in character that of the Italian Subapennine beds, and, like them, often presents a surface denuded of vegetation, in consequence of the action of the rains on soft incohe1·ent materials. In travelling by Paterno, Misterbianco, and La Motta, we pass through deep narrow valleys excavated throu()'h these beds which are sometimes capped, as at La Motta, 0 by columna; basalt, accompanied by strata of tuff and volcanic conglomerate. (Diagram No. 13.) No.l3, La 111olta near Catania. The l~ttcr rock is composed of rolled masses of basalt which ~ay elther. have .originated when £rst the lava was p;oduced n a volca~I~ archtpelago, or subsequently when the whole country w~s nsmg from beneath the level of the sea. Its occurrence m this situation is striking, as not a single pebble can be |
