RECORD: Darwin, C. R. Geological diary: Chili. (2-6.1835) CUL-DAR36.438-444 Transcribed by Kees Rookmaaker, edited by John van Wyhe (Darwin Online, http://darwin-online.org.uk/)

REVISION HISTORY: Transcribed by Kees Rookmaaker, corrected and edited by John van Wyhe 6-8.2011. RN1

NOTE: This document, part of the largest scientific document composed by Darwin during the voyage of the Beagle, is written mostly in ink. Where pencil was used instead this is noted in the textual notes. Marginal notes are here integrated into the text. See the Beagle Diary pp. 553 and following.

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Reproduced with the permission of the Syndics of Cambridge University Library and William Huxley Darwin.

See the introduction to the Geological Diary by Gordon Chancellor.


438

Chili 55

Lines of elevation & volcanos

(The Cauquenas line wd be best here discussed)

With respect to ascertaining the number & kind of lines of elevation, I confess there is much difficulty. From the Campana I had a very good view, but even here this mountain itself sent off such great spurs in all directions & its continuation is traversed by such enormous valleys as that of Quillota, that there must remain much uncertainty respecting the following observations. We have seen, that the cleavage both of the crystalline rock (such as gneiss) & the partly altered slates run generally N by W & S by E. Similarly do the main metal bearing veins. — We all know that the Cordilleras runs about N & S (& indeed as it trends more towards the coast in the latitude of Coquimbo, it must be run towards the W of N) as also do the principal of the subordinate chains situated between the Andes & the Pacific. — Molina generally states generally there are three ([illeg] systems?) (a). I myself could did not observe this uniformity. In the neighbourhead of the Campana there appeared to be five. We have already stated, that in this mountain the greenstone "morro" or hammock (which evidently has caused the elevation of hill) runs N by W or S by E; the hills immediately in the neighbourhead, appear each to be similarly run in same line bearing but they are not all connected in on one continuous crevice. V Diagram. In This renders the counting the chains almost impossible. — to the North the valley of Quillota entirely breaks off the chain to the South it seems continued by a double chain, partly connected by a transverse one, & which I believe, further on from the Cuestas of Prado & Zapata.

(Look to sketch of S. America & scraps in Geology J)

(The Cauquenas line wd be best here discussed)] pencil.

(Look to sketch of S. America & scraps in [sertoges])] pencil.

438 verso

Theoretical drawing representing the crevices of upheaval in the country between Andes & Pacific. —

(b) [sketch] Valparaiso St Jago Andes

(z) Campana of Quillota

NB. Some of these short N & S lines are transversely connected by lower oblique ridges. —

(a) I should rather say there were two principal or high subordinate ranges. — Molina perhaps counts the descent on the coast. —

439

Chili 56

In Some leagues to the South of St Jago, there would appear to be only one band of mountains separating the basins from the plains on the coast. The existence of the inland plains or basins shows, that the next chain to the Andes which is generally a high one, to the Andes has at some little distance from its base. — But here even in this instance we have a proof of the complication of such lines: islands have been mentioned, which dip directly towards the Andes, & at a distance of but a few miles: others dip from the main chain, but at angles of 40° & upwards, these clearly, must belong to different lines, otherwise because these being seated 3 or 4 5 or 6 miles from the main chain, the great dip would give to it an excessive height. Whether the Cordilleras themselves consist of many lines of fissure, with corresponding dips or one grand one I have not yet sufficient evidence. — In almost the whole line, which I have visited, the dip on this west side is very regular & small (apparently not exceeding 10°). The high dips were all found in the lower basal ranges. — This would certainly lead one to suppose there had been one great line of upheaval.

Close to St Jago, the dips were various & some see were directed directly towards the interior. — The chain, at the pass of the Portillo is said to be double: on the East side the Paramillo seems to skirt the mountains, like in the same manner as the subordinate chain of Chili. — The relation of the N & S granitic lines of hills of San Luis seem to belong to some more general order of things, than the elevation of the Cordilleras. —

The occurrence of subordinate lines of hills on the West side is universal

439 verso [blank]

440

Chili 57

from this part of Chili to Tierra del Fuego. V (a) (a). Some of these have contained volcanos (The subject will be discussed when I have more information). Here the more central parts alone of the Cordilleras are traversed by fissure, from which melted rock have flowed. The distinction is not very great as we see in the other lines, that melted stone which has not flowed, has been injected upwards. This would lead to the supposition, that the presence of a volcano is quite of secondary importance. — Generally however they seem to accompany the highest range: This height moreover is not, as has been sometimes supposed, a consequence of the matter ejected, but of the force which propels that matter. — We Granting the great age, which I attribute to the nucleus of the Andes; we must even suppose the formation of volcanos a posterior accident: in as much as volcanoes appear to be limited, not to in duration. —

Mr P. Scrope,1 would I suppose account for the coincidence of line volcanoes & upheaval to the cleavage of rocks, by the easiest mechanical yielding. I cannot help imagining, that the two class of facts are rather owing to some one cause. The horizontal elevation (have N. & S. America [illeg]) & consequent tendency to form fissures has equally, extended in North & South direction from Tierra del Fuego to near the Arctic ocean; & the it is this tendency, which should be described as coincident to the cleavage.

(It signifys not whether the inclined upheaval of mountain ridges has caused the continental horizontal elevations, or vice versâ; the tendency in either case is N. & S. ) — Another argument against Mr Scrope is the direction of greenstone dyke; these certain It might be expected to

1 Scrope 1825.

440 verso

(a) I have already described the strong similarity in form in the intervening spaces between the small plains or land basins of Chili & the channels or great Bayo inland seas of West Patagonia & Tierra del Fuego. —

441

Chili 58

be parallel to the laminae of slates: although this does happen frequently, yet in this country it appears to me by no means generally. — The subject is worthy of consideration. —

With respect to the period of elevation of the subordinate ranges, relatively to the main Cordilleras, I have no proofs. — Some remote conjectures, were provided at Cauquenas, to suppose show they were posterior, drawn from the little degradation of a valley there to compared to the more interior ones of the main chain. — Generally these chains seem quite distinct: the Chacabuco & Talguen (or Tavon) transverse hills, which separate the basin of Aconcagua for Guitron (or St Jago) seem an exception. That such may happen the line of little greenstone paps at St Jago, which is oblique to the Cordilleras is a proof. —

However, as in some cases a N & S line of hills at the base of the Andes (at as at Jajuel, where the dip of strata was small & they seemed part of main range) seems solely to be the effect of degradation. So an E & W one may consist of numerous approximative N & S lines of elevations with their extremities only truncated by degradation. —

With respect to the gneiss hills of Valparaiso (the highest summit of which is 1626 ft) seem entirely owing to the effects of degradation. — Even if a N & S line of chief elevation could be perceived it might be owing to a strand of harder rock, parallel to the cleavage & not to elevation upheaval beneath that line. —

441 verso [blank]

442

Chili 59

The appearances of the Cordilleras have been described in Private Journal as presenting a great barrier, crowned with serrated plains, rather than with a ridge like roof of house. — Here & there there are groups of points or solid cones, which I believe all to be volcanoes or the remains of them. — In space of 60 miles there were four such sets measuring from the two extreme ones of these four. — which would give mean distance of 20 miles one from the other. — I made many enquiries respecting the active volcanoes. An Englishman assured me had seen on one night a volcano at source the Chuapo. — another near the Pass of los Patos & Aconcagua all in action together. — That of los Patos, is celebrated for an immense mass of native copper found there, at a great elevation & believed by the inhabitants to have been melted by the volcano. — The same person assured me that the fire seemed to burst from many apertures at Aconcagua, & this quite agrees with what I could make distinguish of the external figure. — Generally speaking this volcano appears quite inert. —

the 4th volcano is in front of the mine of S. Pedro de Nolasco. — seems is said to me generally in activity called Volcano de St. Jago. — Thence must lie all appear to be seated in central Cordilleras, so that scarcely any of their products & none of their streams of lava have reached the basal exterior parts of the mountains. — There would (a) appear to be a 5th another volcano near Mendoza, from whence the ashes not infrequently fall. — The peak of Cauquenes, probably volcanic, have never known to be active. — The volcano of Peteroa must be seated in very interior parts of the chain, is this the one

442 verso

The peak of Aconcagua is known by angular measurement made by the Beagle to be 2300 ft

(a) I was assured by an intelligent arriero that he has seen smoke issue from the group of mountains called Tupungato. — These lie about a degree S of mendoza, in the central Cordilleras. —

443

Chili 60

mentioned by M. Gay.1 — The Descaborado, a little further to the South is an enormous flat-topped mountain & certainly volcanic: Molina gives an account of emption of Peterra & of 12 active volcanoes in Chili. V. his work. — (a)

Antuco is known to be an active volcano in front of Concepcion: To the North of Valdivia there is the beautiful cone of Villa Rica. Again on terra firma to the the North of Chiloe is a similarly active volcano of Osorno &c. —

These three in this district are the principal & most active ones. But an old Capitan de los Amigos told me he thought there were at least 5 others. — Both Villarica & [Domo] are often in activity. — This part of the Cordilleras would appear to be more studded with craters than any other in southern half of S. America. —

The country intermediate between the Pacifick & central chain is singularly destitute of outlying transverse or parallel subordinate chains. — At the base of these mountains are many great lakes; from information of Capt Fitz Roy the Cordilleras here are very narrow. —

The Pampas on the other side without mountains there are there many salinas. — Mr Douglass3 showed me in shingle beach the kinds of stones, in the outer ranges of Cordilleras in Estero de Reloncavi: they consist all of coarse syenites & granites. —

1 Gay 1838.

2 Molina 1795.

3 Charles Douglas, surveyor and pilot, long resident in Chiloe.

443 verso

(a) There is infinite difficulty in ascertaining from the inhabitants any facts about certain mountains being volcanos. — They give names such as Tupungata & Aconcagua to several peaks or rather to groups of lofty mountains. —

444

1835 Chili (61)

Height [blank] ft

The volcano of Osorno, called also Purraraque, or Hueñanca is [blank] ft above the sea from a very steep pointed & regular one. — Like Villa Rica it stands out, distinct & in front of the Cordilleras. To its South there is another large mountain, likewise separate & perhaps an ancient volcano. — Osorno is very frequently in violent action. 98 miles South of this we have volcano Minchin Madriti out of which I said a small jet of smoke pour rising. — in form is a very obtuse cone, with a broard saddle shaped crater 6729 ft yards across (∠r measurement Mr Sulivan).1

Viewed from the South appears a table shaped mountain. This mountain was known to be a volcano till half a century ago when an immense explosion broke down part of the crater. — is said to emit much sulphureous vapor. — The height is 7621 ft. —

26 miles to South of this we have the Corcobado, 7440 ft high, seated close to the sea, pealed, form not quite regular, sides from with base angle about 33°. — (Villa Rica 26°). — This volcano has one or two strong emptions annually: people in Castro believe, if the Corcobado is quiet for two or three years, a strong earthquake will follow. —

At the foot of the mountain, there is immense quantities of pumice. —

1 Bartholemew James Sulivan (1810-1890), second Lieutenant on the Beagle.

444 verso

I have mentioned, that the two active volcanoes occur to the North of Aconcagua & at no great distance. — From this to the desserts of Atacama I could hear of none (such may however well exist) & at Atacama I heard of two. —

At Iquique, within the Cordilleras, I hear of a solfatara, hot water, steam, sulphur & form of crater. —

At Copiapò it is said there is an extinct crater. —

P. Arena S. Carlos 73°. 56'  
Osornos Lat. 41° 9' 30" Long. 72° 36'
Minchinado — 42° 48' 72 — 34
Corcovado 43 11' 30 72 48
Yanteles 43. 30' 72 50

N of Yanteles (with fine peaks in charts) 18 & 1/2 miles from Corcovado.


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