Geological Observations on South America
- Language:
- English
- Status:
- Complete work
- Authorship:
- Written by the author
- Condition of the text:
- No scanning noise detected (automatic measure over the whole text, not checked by hand)
- Extent:
- ~150,000 words · 701 passages
Cite this work
- APACharles Darwin. (n.d.). Geological Observations on South America. Digital reproduction: SigPhi. https://sigphiai.com/en/works/charles-darwin/geological-observations-on-south-america
- MLACharles Darwin. Geological Observations on South America. Digital reproduction, SigPhi, https://sigphiai.com/en/works/charles-darwin/geological-observations-on-south-america.
- ChicagoCharles Darwin. Geological Observations on South America. Digital reproduction, SigPhi. https://sigphiai.com/en/works/charles-darwin/geological-observations-on-south-america.
Reference to the edition that SigPhi reproduces: SigPhi is its digital reproduction, not its publisher. The edition's year is not in the metadata (hence "n.d."), and the translator appears only when recorded.
What it is about
The third and last of the geological volumes Darwin drew from the Beagle voyage, published in 1846.
Context and history
Darwin sailed as a naturalist but came back above all a geologist, and for years he was better known for that than for anything else. Here he describes the raised marine terraces of the Chilean coast, the fossil beds, the cordilleras and the volcanoes, and concludes that the continent has been rising slowly through immense ages. The experience that settled it he had at first hand: he was in Chile in 1835 when an earthquake lifted the coast several feet in front of him. This is the piece often left out of the story: the notion of deep time and of imperceptible accumulated change came to him from Lyell's geology and from what he saw on land, and without it the argument of 'On the Origin of Species' would not stand up.
Editorial context, not a citable source: unlike the passages of the work itself, these statements cannot be checked against the corpus.
cleavage arise from the development of new minerals, chlorite, epidote or mica, and that in this way a complete graduation from slates to true schists may be traced. Darwin further showed that in highly schistose rocks, the folia bend around and encircle any foreign bodies in the mass, and that in some cases they exhibit the most tortuous forms and complicated puckerings. He clearly saw that in all cases the forces by which these striking phenomena must have been produced were persistent over wide areas, and were connected with the great movements by which the rocks had been upheaved and folded. That the distinct folia of quartz, feldspar, mica, and other minerals composing the metamorphic schists could not have been separately deposited as sediment was strongly insisted upon by Darwin; and in doing so he opposed the view generally prevalent among geologists at that time. He was thus driven to the conclusion that foliation, like cleavage, is not an original, but a superinduced structure in rock-masses, and that it is the result of re-crystallisation, under the controlling influence of great pressure, of the materials of which the rock was composed. In studying the lavas of Ascension, as we have already seen, Darwin was led to recognise the circumstance that, when igneous rocks are subjected to great differential movements during the period of their consolidation, they acquire a foliated structure, closely analogous to that of the crystalline schists. Like his predecessor in this field of inquiry, Mr. Poulett Scrope, Charles Darwin seems to have been greatly impressed by these facts, and he argued from them that the rocks exhibiting the foliated structure must have been in a state of plasticity, like that of a cooling mass of lava. At that time the suggestive experiments of Tresca, Daubree, and others, showing that solid masses under the influence of enormous pressure become actually plastic, had not been published.…