RECORD: Darwin, C. R. Geological diary: Chili. (2-6.1835) CUL-DAR36.429-435 Transcribed by Kees Rookmaaker, edited by John van Wyhe (Darwin Online, http://darwin-online.org.uk/)
REVISION HISTORY: Transcribed by Kees Rookmaaker and John van Wyhe, corrected and edited by van Wyhe, corrections by Gordon Chancellor 6-8.2011. RN2
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.
Their rounded & broken state show that probably they had been cast up on a beach. As these uncovered patches of shells occur at all elevations & in great numbers, it almost proves the land rose during
a great many numerous elevations. Indeed the littoral shells are too abundant to allow the supposition, that any one (or half dozen) elevations could have raised the ground; in as much as, a space of coast of this extent would not probably support as many as we now see lying about the face of the country.
We must consider that almost every part of the
hills land has once remained within tidal influence, that the tops of the hills, formed small outlying h islands, on which the surf threw the shells we see yet lying there. — The highest hill in this district is only 1626 ft; & all below 1300 ft we know has been immersed within the period of recent shells. Bearing Keeping this in mind, I was surprised to see, how far, the features of the country were from bearing the slightest evidence of this fact. — no where, in the sloping valleys was there any lines of beaches or pebbles; the outline of the cliffs, on the coast, was angular; neither did they retain any horizontal lines of particular attention.
I must except, in one place, a few small water-worn little caves, at about 50 ft elevation & generally at 12 to 15 ft above high water line, the gneiss was worn, by the waves. This could not have been solely produced by the earthquake of 1822. —
(a) Mr Alison1 in a letter remarks on the cavities worn into the solid rock at an elevation of about 14 ft above high water mark, & that on a point which could only be reached by climbing, by removing the dung of the sea fowl he discovered Balani
still adhaering to the rock stone. — The coast is steep.
These observations apply to the coast towards the Vino del Mer where also I saw beds of shells at a small elevation.
A similar fact, respecting the Balani, I noticed but rather less than 14 ft although quite removed from the spray,
near on road towards Quintero. —
1 Robert Edward Alison (d. 1854), English author and resident of Valparaiso and later managing director of a Chilean mining company who wrote on South American affairs.
On the coast the ravines are abrupt, narrow & very steep; patches of shells occurring on the edges show that the sea when it retired, had already
modeled the shaped modeled the form: one of these ravine, has formed (& continues doing so) during whole period succession of elevations, a small indentation in the line of coast & which of course it progressively enlarged. Banishing this reasoning, there is nothing in form different from other bold shore, where these ravine, would rather be supposed to be the effect of fresh-water streams rather than the surf of the ocean. — I never walked in the vicinity of Valperaiso, without reflecting that when these shells shall have perished, the most discriminating eye, would could would remove any trace no proof of the land of its recent rise. —
I searched in vain for proofs of the epoch of rise of the land. —
To the North of Valparaiso, at Quintero & Concon, there are numerous beds of recent shells; those which I saw, were of one kind (a Donex?) (2242); they
at lie loose, mixed with little earth; to the the bed has a thickness of some feet; are worked for lime; under a 100 ft elevation above the sea. — The recent living shells of same species, are abundant in large collections in flat tidal sand flats. —
The most southern point, where I clearly saw this phenomenon was in the valley of Vacalema (a), near the village; there were also beds of the same sorts of broken shells, on the
plains height bordering high plain & its edges & little sinuosities. This by Miers map1 is about 10 miles from the coast. —
1 Miers 1826.
(a) At S. Antonio shells are thus mined, collected & burnt for line. This is 5 miles South of Valparaiso. & 15 North of Bacalemu
Again, they were present at the bottom of the great deep valley of the R. Maypo, some miles from the coast. —
M. Gay1 states he found such near
Topocalmo Navadad, 2 leagues inland in low places. perhaps the valley of the Repels. (a) — I was exceedingly exceedingly struck with these facts 7 was meditating during my ride, how completely nearly exclusively the waves of the sea in this country have modeled the outline of even the minuter features of this country; all the arguments stated at length, to prove the marine origin of the island basins & main valleys, were present in my mind. — Yet I had just returned from seeing the devastating effects of the torrents in the Cordilleras. At this opportune time, the road (to Case Blanca) crossed a valley, with a small streamlet; the name of which "Quebrada onda" (deep ravine) expresses its abrupt depth (perhaps 600 ft? or more?); it is not broard, or flat-bottomed; is scooped out through gneiss. —
Here was a puzzle — considering its form I inclined to the common doctrine of running water: but the question was solved, against me, by finding at the very bottom & in the middle a large bed of shells, exclusively composed of the "Donax" (
of likely at Quintero). They rested on muddy sand. —
There being no other sorts, renders it highly probable, if not certain, that the sea left the in their present position (otherwise they would have mingled with the marine remaining). Yet this is only 3 feet above the present stream: I have said this stream is very small:
yet but its effects on the valley are still smaller. —
1 Gay 1838.
(a) near the mouth of the Rapal. I saw barnacles adhaering to rock some ft above level of highest tides. — There were shells on the surface of the gravel about 100 ft above same level. —
[sketch] A shells
In this valley, there was
pres other presumptive evidence of the residence of the sea & That at different periods it was differently circumstanced, viz at one time it deposited soft coarse sandstone & calcareous matter in horizontal beds as at (A) subsequently to the part of the valley being scooped out: this latter process was again continued & the deposits almost removed & the valley deepened. —
From what I have seen in Chili (& indeed with less evidence in Patagonia & Chiloe) I cannot impress the idea too forcibly, that the sea has been, in the more level parts, almost the sole agent in impressing the usual configuration of continents. I do not say this, without having seen something of the powers of running water. — In the valley of Cauquenes, I saw the porphyry as plainly marked by
the grooves 50 feet above the river, as in its very bed. Yet it appears to me, in such hard tough material, the chief only chief effect is to cut nearly vertical gorges. — I am assured, during the winter floods, the small streams hurl fragments of rock, yards square in dimensions. — Every thing bespeaks their fury & power; but this is where the inclination is great & the power of carrying pebbles is exerted in a corresponding degree. — With respect to the sea above reasoning, I allude to the larger valleys, with less inclination. — in these, the summer floods, doubtless are most impetuous, but the great mass of pebbles, over which they flow, must act like friction balls one over the other, & so that as long as the supply is abundant, the effect on the bottom must
432 verso [blank]
be nearly nullified. — The grandeur of the valleys in the Cordilleras is perhaps one of their most striking characters: the regularity on each side & smallness of dip of strata show what enormous wedge-shaped masses have been removed,
which have left leaving only spurs to divide the valleys: This would have been effected. We should be able to comprehend the power better, if we might conjecture, that the outer lines of hills have been posteriorly elevated, so as to protect the former weather beaten coast. The view, of the great flat [illeg] valleys, such as Quillota from the summit of the Campana, is even more astonishing: it is manifest this valley has cut through, removed, & leveled, has several parts of several of the lofty N & S ranges of hills. Its original course, was probably determined by points of lower upheaval, as at Cauquenes. —
When the reason refuses to admit, the vast, the almost incomprehensible powers of destruction in water, it is well to recollect the shingle plains of Patagonia: perhaps if the bottom of Pacific was exposed to view, our wonder would be reversed, we should only marvel, that part of the Andes yet remained fixed. —
The sea, appears much better adapted to excavate any broard valley or basin, than
any rivers; because its power (in proportion as open to swell of ocean) increases is in regular process relatively is chiefly exerted on the coast line, & in the same ratio as this must increase in extent (as from the centre o a circle), & in the same ratio will the power. Moreover
The flowing tide brings in clear water, the ebb carries out some sediment,
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These valleys, which connect the sea and islands basins are somewhat connected with the class of S. Cruz (old straights valleys) where the influence of tides between two seas, must always be most corroding agent. The basins may be considered lesser seas.—
but in this better respect, I do not suppose the sea at all equals the powers of a river.
As I have [wh] said One of these valleys (& why not all many others? which are not excepting the very tortuous. & have clearly formed by running water:) are may be considered, as the prolongation, or the succession, at different altitudes, of a bay:
Thus, we generally see at the head of all bays,
in all countries, a broard valley (b), by raising the water, we should increase the limits of the bay, only with a natural outline. —
All the above arguments are felt with more force in Chili, where we know that within the period of recent shells, the
water sea stood intersects by land 1200 ft above its present level. —
I am inclined to think many valleys all over the world have been formed on this principle of a succession of bays, sinking vertically but extending horizontally & subsequently modified. — Many of the arguments in Note XVI of Playfair Hutt: Theory on rivers & lakes (p 350)
apply equally respecting the "regular communication of greatest depression"1 as a proof that the river itself has excavated its valley equally applies to the above principle. — Considering the elevation of a continent from the moment, when its highest mountains were ridges, every little valley cove would determine a line of valley; (as seen in Chiloe) and which though which tend all the chain even encircling. in any one basin as the land rose, would tend towards the line of seas deepest bed, & this would ultimately form the main line of valley. This supposes very regular elevation. I by no means wish to say, that many valleys of rivers are not a system of lakes or irregularities, gradually corroded into one line. It appears to me that Playfair proves too much. How much more If we Let us consider the valleys, formed across a sedimentary plain, which arise from any chain of mountains. it is well known that in front of each great undulation in that chain, the bottom water would be rather deeper (owing tides & [illeg] forms of land, on which deposits have collected), or there would be a corresponding depression in the bottom — now when the first belt of strata were elevated, there would still be a bay at that spot & the process would be continued always, as the land rose leaving a valley behind it, which would exactly correspond with the great original indentation or valley in the chain of mountains. —
N.B. I have formerly shown that a straits with rivers would, when uplifted form a valley & lakes, the drainage would however in this case take place probably towards both extremities. Judging from the maps is not this the case, with the Lochs which run by Fort William is (100 miles long) (where the terraces occur?) V Playfair p. 404
With respect to Mr Playfairs arguments of inlets in a bold coast corresponding with rivers, I cannot agree with him that the river has
cut through especially scored them out. P. 370. XX In these cases especially, where the sea sends in long arms, the effect of the river can be nothing (except to chunk up the inlet!). Hence then the sea, working on original fissure or depression, is the excavating agent; apply this force at higher levels & the whole valley may be thus formed. —
(a) I certainly especially on this coast of S. America
XX The illustration of the indented coast of Norway is unfortunate, as the coast is known to have been elevated within a recent period, & the probability of the rivers having opened passages for the sea to enter far less.
(100 miles long)] pencil insertion.
V Playfair p. 404] pencil insertion.
p. 370. XX] later ink insertion.
working on original fissure or depression] later ink insertion.
simple it is to account for, by the agency of the sea, of the enormous mass of alluvium, which is said to occur "in very many instances, & which causes the difficulty "so generally" experienced in
building [Lindy's] foundations for bridges in large valleys or plains. — By Mr Playfairs theory, the whole course of main valley, XX must have been a necklace of lakes & these all broken down. — here the valley traverses a plain, how can he account for the existence of so many supposed lakes. Any how it is With respect to the terraces on each side or "haughs", I have at St Cruz shown that they prove the residence of the sea. — Anyhow it is certain, that at every different period of elevation of a continent, the sea must have sent creeks & bays into all the lines of lowest level, these must by the action of the surf become more or less bounded, & where elevated uplifted into dry land would be the line of drainage for the interior parts in that vicinity. — The subsequent effects of the river I by no means want to underrate. — See S Cruz Valley
XX where to build a barriers for the supposed lakes is more difficult
N.B. From p: 165 to 192, further detailed descriptions of valleys, N. of Valparaiso
The ultimate conclusion which I
draw have come to — Is that primarily the lines of elevation determine the figure of a continent; secondarily that a gradually retreating ocean models the elevated points, smooths with so called Diluvium some of its asperities determines the directions of the great slopes. — & not unfrequently sometimes examples similar sometimes [illeg] every the number valleys —
Thirdly we have rivers with aid of floods & subterranean movements modifying altering & generally deepening those lines of depression left by the preexisting ocean. — The two former
underlining on this page is in pencil.
See S Cruz Valley] pencil insertion.
(a) & not unfrequently even excavates the valleys ( — I take however the term not in its most confined sense). —
Why do the boundaries of the plains of a valley expand near
the its mouth like the shores of an aestuary? Does not the river in its lower part become more powerless? Is it not then more generally an agent in forming instead of removing land? If the above simile is taken as an explanation it is at the same time an answer. —
It was an aestuary. — The cause why such inlets expand uniformity must be sought in the fact
of a regular slope of the land seemed, that the sea has tendency from currents & outer parts most exposed, to wear every indentation in form of a wedge. — XXX
The action of the surf on its coast proceeds in an
geological increasing (2) ratio (1), as the length extent of the surface is an entangled. — It will also be more violent always in the outer parts. —
If I argued generally for marine origin of common valleys, I would ground my argument on the above fact & the Diluvium found so very generally beneath, as well as above the
surface level of rivers, in the wider parts of valleys. —
XXX. The form of this wage must be continued beneath water outward; so that after each elevation, the new mouth is wider than the former.
Line of new coast after elevation. —
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Citation: John van Wyhe, editor. 2002-. The Complete Work of Charles Darwin Online. (http://darwin-online.org.uk/)
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