Darwin the Geologist

2009 marks the bicentenary of the birth of Charles Robert Darwin, and the 150 year anniversary of the publication of “On the Origin of Species by Means of Natural Selection, or The Preservation of Favoured Races in the Struggle for Life.“
But let us remember also that Darwin – against his own preconceptions- worked also as geologist.

Notebook M, 1838, page 39

August 1831 Ch. Darwin accompanied Professor Adam Sedgwick (1785-1873, considered one of the founding fathers of geology in England) on a geologic tour of North Wales. Twenty pages of notes made by Darwin during the tour are today conserved the Cambridge University Library, and they are extremely valuable because they provide first-hand insight into both Darwin's geological knowledge and his scientific philosophy at this time in his life. Remarkably, when Darwin returned from the North Wales tour to his home at Shrewsbury, in Shropshire, he received Captain FitzRoy's offer for the position of naturalist on board H.M.S. Beagle.

Charles Darwin by G. Richmond (1830)

The circumstances which led to the joint tour in Wales were fortuitous and are somewhat puzzling. Sedgwick was forty-six years old and professor of geology at Cambridge, with years of geo-experience in Scotland, the Alps, Cumberland, and South Wales, and in 1831 he was anxious to extend his studies into North Wales. In contrast, Darwin had just graduated from Cambridge University in the spring of 1831. When a student at Edinburgh University during the years 1825-1827, he had been repelled by geology while attending Professor Robert Jameson's classes. To Darwin, Jameson's explanation of igneous veins being filled from above seemed absurd. As a result, Darwin resolved at that time never again to study the subject. In fact after Jameson he never again actively joined a geology-lecture.

It seemed also unlikely therefore, that Darwin and Sedgwick would have gone together on such a tour. Only by the intervention of John Henslow, professor of botany at Cambridge and friend of Charles, Darwin was convinced to join the geologist on this tour. Anyway, Henslow, himself an excellent geologist, had taken Darwin on innumerable natural history walks around Cambridge. Darwin would obviously have learned much geology from Henslow, and of course Henslow would have become well acquainted with Darwin's geological abilities.

We know from Darwin's early correspondence, when he was a schoolboy in Shrewsbury, of his precocity in chemistry and mineralogy. One letter, which is now preserved in Cambridge University's Robin Darwin Collection, illustrates these early interests. The letter, from Charles's older brother Erasmus, gives him detailed instructions in mineral identification. At this time Charles was only thirteen years of age.

The tour not only gave Darwin the possibility to experience geology in the field with a highly recommended geologist, but also to learn to handle a difficult personality – a lesson that during the 5-year voyage on the Beagle cam handle with the strong (some maybe will say fanatic) personality of Captain Robert FitzRoy.

After his voyage (1831-1836), the first edition of the "The structure and distribution of coral reefs" was published 1842. The "Geological Observations on the Volcanic Islands" was published in the year 1844, followed 1846 by the "Observations on South America", as final part of the geological research carried aut during the voyage of the Beagle.
The first volume covered the distribution and structure of coral-riffs, the second contained the descriptions of the visited volcanic islands, and a short notification about the geology of the south African cap-region and Australia, the third finally covers the geology of the south American continent.

Darwins also published some minor papers, in 1846 a description about the geology of the Falkland Islands, in 1838 about some phenomenon’s observed during the volcanism in South America, in 1841 about erratic blocks distribution and some unstratified sediments in South America and in 1845 observations about the dusk that can be found, transported by wind on ships in the Atlantic ocean.

In his work of 1844 he describes as most prominent features the geology of the island of Ascension, St. Helena and last but not least the Galapagos. On Ascension he was fascinated by the of Obsidian, and the laminated (flow) features that this natural glass can show.

On the Galapagos island he carefully study the features of the fluidity of lava flows - he states that "The degree of fluidity in different lavas, does not seem to correspond with any apparent corresponding amount of difference in their composition" - this is not completely true, the viscosity of lava depends of the amount of silica.

He correctly observes that a differentiation of magma is possible by segretation of minerals by gravity - a fundamental point to explain the different lava types found on earth.
"Much of the difficulty which geologists have experienced, when they have compared the composition of volcanic with plutonic formations, will, I think, be removed, if we may believe, that most plutonic masses have been, to a certain extent, drained of those comparatively weighty and easily liquefied elements, which compose the trappean and basaltic series of rocks."

ONLINE REFERENCES

BARRETT, P. H. (1974): The Sedgwick-Darwin geologic tour of North Wales. Proceedings of the American Philosophical Society 118, No. 2. (19 April): 146-164.
DARWIN, C. R. (1836): Geological notes made during a survey of the east and west coasts of S. America, in the years 1832, 1833, 1834 and 1835, with an account of a transverse section of the Cordilleras of the Andes between Valparaiso and Mendoza. [Read by A. Sedgwick 18 November 1835] Proceedings of the Geological Society 2: 210-212.
DARWIN, C. R. (1837): Observations of proofs of recent elevation on the coast of Chili, made during the survey of His Majesty's Ship Beagle commanded by Capt. FitzRoy R.N. [Read 4 January] Proceedings of the Geological Society of London 2: 446-449.
DARWIN, C. R. (1837): A sketch of the deposits containing extinct Mammalia in the neighbourhood of the Plata. [Read 3 May] Proceedings of the Geological Society of London 2: 542-544.
DARWIN, C. R. (1837): On certain areas of elevation and subsidence in the Pacific and Indian oceans, as deduced from the study of coral formations. [Read 31 May] Proceedings of the Geological Society of London 2: 552-554.
DARWIN, C. R. (1838): On the connexion of certain volcanic phaenomena, and on the formation of mountain-chains and volcanos, as the effects of continental elevations. [Read 7 March] Proceedings of the Geological Society of London 2: 654-660.
DARWIN, C. R. (1839): Observations on the parallel roads of Glen Roy, and of other parts of Lochaber in Scotland, with an attempt to prove that they are of marine origin. [Read 7 February] Philosophical Transactions of the Royal Society 129: 39-81.
DARWIN, C. R. (1839): Note on a rock seen on an iceberg in 61° south latitude. Journal of the Royal Geographical Society of London 9 (March): 528-529.
DARWIN, C. R. (1840): On the connexion of certain volcanic phenomena in South America; and on the formation of mountain chains and volcanos, as the effect of the same powers by which continents are elevated. [Read 7 March] Transactions of the Geological Society of London (Ser. 2) 5 (3): 601-631, pl. 49, fig. 1.
DARWIN, C. R. (1840): On the formation of mould. [Read 1 November 1837] Transactions of the Geological Society (Ser. 2) 5 (2): 505-509
DARWIN, C. R. (1841): On a remarkable bar of sandstone off Pernambuco, on the coast of Brazil. The London, Edinburgh and Dublin Philosophical Magazine (Ser. 3) 19 (October): 257-260, 1 text figure.

DARWIN, C. R. (1842): The structure and distribution of coral reefs. Being the first part of the geology of the voyage of the Beagle, under the command of Capt. Fitzroy, R.N. during the years 1832 to 1836. London: Smith Elder and Co.
DARWIN, C. R. (1842): On the distribution of the erratic boulders and on the contemporaneous unstratified deposits of South America. [Read 14 April 1841] Transactions of the Geological Society Part 2, 3 (78): 415-431.
DARWIN, C. R. (1842): Notes on the effects produced by the ancient glaciers of Caernarvonshire, and on the boulders transported by floating ice. The London, Edinburgh and Dublin Philosophical Magazine 21 (September): 180-188.
DARWIN, C. R. (1844): Geological observations on the volcanic islands visited during the voyage of H.M.S. Beagle, together with some brief notices of the geology of Australia and the Cape of Good Hope. Being the second part of the geology of the voyage of the Beagle, under the command of Capt. Fitzroy, R.N. during the years 1832 to 1836. London: Smith Elder and Co.
DARWIN, C. R. (1876): Geological observations on the volcanic islands and parts of South America visited during the voyage of H.M.S. 'Beagle'. 2d edition. London: Smith Elder and Co.