[169]

Account of eruption of Volcano of Cauquenes Peuquenes

Journal of Natural and Geographical Science August 1830 ─ Dr. Gillies

NB. Volcano south of the Pass of Portillo no doubt generally called Maypo. ─ C.D.

First recorded eruption state of activity subsequent to shock of 1822, often since in activity

x In Portillo P. ─ Mendoza range highest; pass 14.365 extended with very little interruption, as far as R. Diamente which is 140 miles to S.─ The pass of Peuquenes is 13,210

Valley of Tenuyan, where road crossed river 7530.─ (My section must be altered) Ashes often fall at Mendoza

Winds generally from Pacific as known by ashes.─ The volcano summit is generally covered with snow and its elevation cannot be less than 15,000 feet, above the level of the sea"

[South America, p. 186: "This great range, according to Dr. Gillies, can be traced with little interruption for 140 miles southward to the R. Diamante, where it unites with the western ranges: northward, according to this same author, it terminates where the R. Mendoza debouches from the mountains; but a little further north in the eastern part of the Cumbre section, there are, as we shall hereafter see, some mountain-masses of a brick-red porphyry, the last injected amidst many other porphyries, and having so close an analogy with the coarse red granite of the Portillo line, that I am tempted to believe that they belong to the same axis of injection; if so, the Portillo line is at least 200 miles in length. Its height, even on the lowest gap in the road, is 14,365 feet, and some of the pinnacles apparently attain an elevation of about 16,000 feet above the sea. The geological history of this grand chain appears to me eminently interesting. We may safely conclude, that at a former period the valley of Tenuyan existed as an arm of the sea, about twenty miles in width, bordered on one hand by a ridge or chain of islets of the black calcareous shales and purple sandstones of the Gypseous formation; and on the other hand, by a ridge or chain of islets composed of mica-slate, white granite, and perhaps to a partial extent of red granite. These two chains, whilst thus bordering the old sea-channel, must have been exposed for a vast lapse of time to alluvial and littoral action, during which the rocks were shattered, the fragments rounded, and the strata of conglomerate accumulated to a thickness of at least 1500 or 2000 feet."]

[169v]

The two ranges are separated from each other by wide valley for about twenty miles.─ Portillo range commences at Rio Mendoza. The Peuquenes range joins on the Portillo to south ─ The river crosses by a deep chasm or valley, which it seems to have formed for closely (NB. is not this the character of th Bolivian ravines?)