The Structure and Distribution of Coral Reefs
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, was published in 1842 as
The book was the first volume of three Darwin wrote about the geology he had investigated during the voyage, and was widely recognised as a major scientific work that presented his deductions from all the available observations on this large subject.[1] In 1853, Darwin was awarded the Royal Society's Royal Medal for the monograph and for his work on barnacles.[2] Darwin's theory that coral reefs formed as the islands and surrounding areas of crust subsided has been supported by modern investigations, and is no longer disputed, while the cause of the subsidence and uplift of areas of crust has continued to be a subject of discussion.[3]
Theory of coral atoll formation
When the Beagle set out in 1831, the formation of
The circularly-formed Coral Islands in the Pacific occasionally afford excellent land-locked harbours, with a sufficient entrance, and would be well adapted to any nice astronomical observations which might require to be carried on in undisturbed tranquillity. While these are quietly proceeding, and the chronometers rating, a very interesting inquiry might be instituted respecting the formation of these coral reefs .... A modern and very plausible theory has been put forward, that these wonderful formations, instead of ascending from the bottom of the sea, have been raised from the summits of extinct volcanoes ...[6]
As a student at the
While the Beagle surveyed the coasts of South America from February 1832 to September 1835, Darwin made several trips inland and found extensive evidence that the continent was gradually rising. After witnessing an erupting volcano from the ship, he experienced the 1835 Concepción earthquake. In the following months he speculated that as the land was uplifted, large areas of the ocean bed subsided. It struck him that this could explain the formation of atolls.[5][12][13]
Darwin's theory followed from his understanding that coral polyps thrive in the clean seas of the tropics where the water is agitated, but can only live within a limited depth of water, starting just below low tide. Where the level of the underlying land stays the same, the corals grow around the coast to form what he called fringing reefs, and can eventually grow out from the shore to become a barrier reef. Where the land is rising, fringing reefs can grow around the coast, but coral raised above sea level dies and becomes white limestone. If the land subsides slowly, the fringing reefs keep pace by growing upwards on a base of dead coral, and form a barrier reef enclosing a lagoon between the reef and the land. A barrier reef can encircle an island, and once the island sinks below sea level a roughly circular atoll of growing coral continues to keep up with the sea level, forming a central lagoon. Should the land subside too quickly or sea level rise too fast, the coral dies as it is below its habitable depth.[1]
Darwin's investigations to test his theory
By the time that the Beagle set out for the Galápagos Islands on 7 September 1835, Darwin had thought out the essentials of his theory of atoll formation. While he no longer favoured the concept that atolls formed on submerged volcanos, he noted some points on these islands which supported that idea: 16 volcanic craters resembled atolls in being raised slightly more on one side, and five hills appeared roughly equal in height. He then considered a topic which was compatible with either theory, the lack of coral reefs around the Galápagos Islands. One possibility was a lack of calcareous matter around the islands, but his main proposal, which FitzRoy had suggested to him, was that the seas were too cold. As they sailed on, Darwin took note of the records of sea temperature kept in the ship's "Weather Journal".[14]
He had his first glimpse of coral atolls as they passed
Keeling Islands
FitzRoy's instructions set detailed requirements for geological survey of a circular
These soundings were taken personally by FitzRoy, and the tallow from each sounding was cut off and taken on board to be examined by Darwin.[19] The impressions taken on the steep outside slope of the reef were marked with the shapes of living corals, and otherwise were clean down to about 10 fathoms (18 m); then at increasing depths, the tallow showed fewer such impressions and collected more grains of sand until it was evident that there were no living corals below about 20–30 fathoms (36–55 m).[20] Darwin carefully noted the location of the different types of coral around the reef and in the lagoon.[21] In his diary, he described, "examining the very interesting yet simple structure & origin of these islands. The water being unusually smooth, I waded in as far as the living mounds of coral on which the swell of the open sea breaks. In some of the gullies & hollows, there were beautiful green & other colored fishes, & the forms & tints of many of the Zoophites were admirable. It is excusable to grow enthusiastic over the infinite numbers of organic beings with which the sea of the tropics, so prodigal of life, teems", though he cautioned against the "rather exuberant language" used by some naturalists.[22]
As they left the islands after eleven days, Darwin wrote out a summary of his theory in his diary:
Throughout the whole group of Islands, every single atom, even from the most minute particle to large fragments of rocks, bear the stamp of once having been subjected to the power of organic arrangement. Capt. FitzRoy at the distance of but little more than a mile from the shore sounded with a line 7200 feet long, & found no bottom. Hence we must consider this Isld as the summit of a lofty mountain; to how great a depth or thickness the work of the Coral animal extends is quite uncertain.... Under this view, we must look at a Lagoon Isd as a monument raised by myriads of tiny architects, to mark the spot where a former land lies buried in the depths of the ocean.[23]
Publication of theory
When the Beagle returned on 2 October 1836, Darwin was already a celebrity in scientific circles, as in December 1835
Darwin's first literary project was his Journal and Remarks on the natural history of the expedition, now known as The Voyage of the Beagle. In it he expanded his diary notes into a section on this theory, emphasising how the presence or absence of coral reefs and atolls can show whether the ocean bed is elevating or subsiding.[28] At the same time he was privately speculating intensively about transmutation of species, and taking on other projects. He finished writing out his journal around the end of September, but then had the work of correcting proofs.[29]
His tasks included finding experts to examine and report on his collections from the voyage. Darwin proposed to edit these reports, writing his own forewords and notes, and used his contacts to lobby for government sponsorship of publication of these findings as a large book. When a Treasury grant of £1,000 was allocated at the end of August 1837, Darwin stretched the project to include the geology book that he had conceived in April 1832 at the first landfall in the voyage. He selected Smith, Elder & Co. as the publisher, and gave them unrealistic commitments on the timing of providing the text and illustrations. He assured the Treasury that the work would be good value, as the publisher would only require a small commission profit, and he himself would have no profit.[30][31] From October he planned what became the multi-volume Zoology of the Voyage of H.M.S. Beagle on his collections, and began writing about the geology of volcanic islands.[29]
In January 1838, Smith, Elder & Co. advertised the first part of Darwin's geology book, Geological observations on volcanic islands and coral formations, as a single octavo volume to be published that year. By the end of the month Darwin thought that his geology was "covering so much paper, & will take so much time" that it could be split into separate volumes (eventually Coral reefs was published first, followed by Volcanic islands in 1844, and South America in 1846). He also doubted that the treasury funds could cover all the geological writings. The first part of the zoology was published in February 1838, but Darwin found it a struggle to get the experts to produce their reports on his collections, and overwork led to illness.[32][33] After a break to visit Scotland, he wrote up a major paper on the geological "roads" of Glen Roy.[34] On 5 October 1838 he noted in his diary, "Began Coral Paper: requires much reading".[35]
In November 1838 Darwin proposed to his cousin
gloomy & tired— the government money has gone much quicker than I thought & the expences of the coral-volume are greater being, as far as we can judge from 130£ to 140£.— How I am publish the remainder I know not, without taking 2 or 300£ out of the funds—& what will you say to that.— I am stomachy & be blue deviled— I am daily growing very very old, very very cold & I daresay very sly. I will give you statistics of time spent on my coral-volume, not including all the work on board the Beagle— I commenced it 3 years & 7 months ago, & have done scarcely anything besides— I have actually spent 20 months out of this period on it! & nearly all the remainder sickness & visiting!!![37]
Publication and subsequent editions
The Structure and Distribution of Coral Reefs was published in May 1842, priced at 15 shillings, and was well received. A second edition was published in 1874, extensively revised and rewritten to take into account James Dwight Dana's 1872 publication Corals and Coral Islands, and work by Joseph Jukes.[8][38]
Structure of book
The book has a tightly logical structure, and presents a bold argument. Illustrations are used as an integral part of the argument, with numerous detailed charts and one large world map marked in colour showing all reefs known at that time. A brief introduction sets out the aims of the book.[1]
The first three chapters describe the various types of coral reef, each chapter starting with a section giving a detailed description of the reef Darwin had most information about, which he presents as a typical example of the type. Subsequent sections in each chapter then describe other reefs in comparison with the typical example. In the first chapter, Darwin describes atolls and lagoon islands, taking as his typical example his own detailed findings and the Beagle survey findings on the Keeling Islands. The second chapter similarly describes a typical barrier reef then compares it to others, and the third chapter gives a similar description of what Darwin called fringing or shore reefs.[1] Having described the principal kinds of reef in detail, his finding was that the actual surface of the reef did not differ much. An atoll differs from an encircling barrier reef only in lacking the central island, and a barrier reef differs from a fringing reef only in its distance from the land and in enclosing a lagoon.[39]
The fourth chapter on the distribution and growth of coral reefs examines the conditions in which they flourish, their rate of growth and the depths at which the reef building polyps can live, showing that they can only flourish at a very limited depth. In the fifth chapter he sets out his theory as a unified explanation for the findings of the previous chapters, overcoming the difficulties of treating the various kinds of reef as separate and the problem of reliance on the improbable assumption that underwater mountains just happened to be at the exact depth below sea level, by showing how barrier reefs and then atolls form as the land subsides, and fringing reefs are found along with evidence that the land is being elevated. This chapter ends with a summary of his theory illustrated with two woodcuts each showing two different stages of reef formation in relation to sea level.[40]
In the sixth chapter he examines the geographical distribution of types of reef and its geological implications, using the large coloured map of the world to show vast areas of atolls and barrier reefs where the ocean bed was subsiding with no active volcanos, and vast areas with fringing reefs and volcanic outbursts where the land was rising. This chapter ends with a recapitulation which summarises the findings of each chapter and concludes by describing the global image as "a magnificent and harmonious picture of the movements, which the crust of the earth has within a late period undergone".[39] A large appendix gives a detailed and exhaustive description of all the information he had been able to obtain on the reefs of the world.[1]
This logical structure can be seen as a prototype for the organisation of On the Origin of Species, presenting the detail of various aspects of the problem, then setting out a theory explaining the phenomena, followed by a demonstration of the wider explanatory power of the theory. Unlike the Origin which was hurriedly put together as an abstract of his planned "big book", Coral Reefs is fully supported by citations and material gathered together in the Appendix. Coral Reefs is arguably the first volume of Darwin's huge treatise on his philosophy of nature, like his succeeding works showing how slow gradual change can account for the history of life. In presenting types of reef as an evolutionary series it demonstrated a rigorous methodology for historical sciences, interpreting patterns visible in the present as the results of history. In one passage he presents a particularly Malthusian view of a struggle for survival – "In an old-standing reef, the corals, which are so different in kind on different parts of it, are probably all adapted to the stations they occupy, and hold their places, like other organic beings, by a struggle one with another, and with external nature; hence we may infer that their growth would generally be slow, except under peculiarly favourable circumstances."[1]
Reception
Having successfully completed and published the other books on the geology and zoology of the voyage, Darwin spent eight years on a major study of barnacles. Two volumes on Lepadidae (goose barnacles) were published in 1851. While he was still working on two volumes on the remaining barnacles, Darwin learnt to his delight in 1853 that the Royal Society had awarded him the Royal Medal for Natural Science. Joseph Dalton Hooker wrote telling him that "Pordock proposed you for the Coral Islands & Lepadidae, Bell followed seconding on the Lepadidae alone, & then followed such a shout of paeans for the Barnacles that you would have [smiled] to hear."[2]
Late 19th-century controversy and tests of the theory
A major scientific controversy over the origin of coral reefs took place in the late 19th century, between supporters of Darwin's theory (such as the American geologist
A series of expeditions to test Darwin's theory by drilling on
Darwin's findings and later views
Darwin's interest on the biology of reef organisms was focussed on aspects related to his geological idea of subsidence; in particular, he was looking for confirmation that the reef building organisms could only live at shallow depths. FitzRoy's
In assessing the geology of the reef, Darwin showed his remarkable ability to collect facts and find patterns to reconstruct geological history on the basis of the very limited evidence available. He gave attention to the smallest detail. Having heard that
His observations on the part played by organisms in the formation of the various features of reefs anticipated later studies. To establish the thickness of coral barrier reefs, he relied on the old nautical rule of thumb to project the slope of the land to that below sea level, and then applied his idea that the coral reef would slope much more steeply than the underlying land. He was fortunate to guess that the maximum depth of coral would be around 5,000 ft (1,525 m), as the first test bores conducted by the
In Darwin's global hypothesis, vast areas where the seabed was being elevated were marked by fringing reefs, sometimes around active volcanoes, and similarly huge areas where the ocean floor was subsiding were indicated by barrier reefs or atolls based on inactive volcanoes. These views received general support from deep sea drilling results in the 1980s. His idea that rising land would be balanced by subsidence in ocean areas has been superseded by plate tectonics, which he did not anticipate.[45]
See also
- Formation of coral reefs
- Darwin's paradox
- List of reefs
- Zimmerman's Competing Theory of Reef Formation
Notes
- ^ a b c d e f g Gordon Chancellor (2008), Introduction to Coral reefs, Darwin Online, retrieved 20 January 2009
- ^ a b Browne 1995, p. 509
- ^ Rosen 1982, p. 524
- ^ Herbert 2005, p. 168
- ^ a b Herbert 1991, pp. 186–190
- ^ a b FitzRoy 1839, pp. 38–39
- ^ Browne 1995, pp. 183–190
- ^ a b Freeman, R. B. (1977), Geology of The Voyage of The Beagle, Darwin Online, retrieved 22 January 2009
- ^ Lyell 1830, p. 212
- ^ Lyell 1832, pp. 283–298
- ^ Herbert 2005, p. 68
- ^ Darwin 1958, pp. 98–99
- ^ Gordon Chancellor; John van Wyhe (August 2008), 'State this with clearness': an introduction to the Santiago Notebook, Darwin Online, retrieved 23 January 2009
- ^ a b Herbert 1991, pp. 188–190
- ^ Keynes 2001, pp. 364–378
- ^ Darwin 1962, pp. 2–3
- ^ Darwin 1962, pp. 12–17
- ^ FitzRoy 1839, pp. 629–637.
- ^ Darwin 1842, pp. 7
- ^ Darwin 1845, pp. 467–468.
- ^ Darwin 1842, pp. 5–17
- ^ Keynes 2001, pp. 413–419.
- ^ Keynes 2001, p. 418.
- ^ Darwin 2002–2008, editorial introduction
- ^ Desmond & Moore 1991, pp. 201–202
- ^ Darwin 1887, pp. 324–325
- ^ Darwin 1837
- ^ Darwin 1839, pp. 553–569
- ^ a b Darwin 2006, pp. 13 recto, 1837–verso, 1838
- ^ Browne 1995, pp. 186, 367–369
- ^ Letter 378a – Darwin, C. R. to Spearman, A. Y., 20 Sept 1837, Darwin Correspondence Project, retrieved 16 July 2009
- ^ Browne 1995, pp. 372–373
- ^ Letter 400 – Darwin, C. R. to Henslow, J. S., (21 Jan 1838), Darwin Correspondence Project, retrieved 16 July 2009
- ^ Browne 1995, pp. 381–373
- ^ Darwin 2006, pp. 15 verso, 1838
- ^ van Wyhe 2007, pp. 186–187
- ^ Letter 626 – Darwin, C. R. to Darwin, Emma, (9 May 1842), Darwin Correspondence Project, retrieved 16 July 2009
- ^ Darwin 1874
- ^ a b Darwin 1842, pp. 147–148
- ^ Darwin 1842, pp. 98–118
- ^ ISBN 0-375-42161-0
- ISBN 0 642 10791 2
- ^ David, Mrs Edgeworth, Funafuti or Three Months On A Coral Atoll: an unscientific account of a scientific expedition, London: John Murray, 1899
- .
- ^ a b c Rosen 1982, pp. 520–524
- ^ Darwin 1842, pp. 14–15
References
- ISBN 1-84413-314-1
- Darwin, Charles (15 December 1962), Stoddart, D. R. (ed.), "Coral Islands by Charles Darwin, with Introduction, map and remarks", Atoll Research Bulletin, no. 88, Washington, D. C.: The Pacific Science Board, National Academy of Sciences—National Research Council, pp. 1–20, retrieved 22 January 2009
- Darwin, Charles (2002–2008), John van Wyhe (ed.), "Extracts from letters to Professor Henslow", Darwin Online, retrieved 20 January 2009
- 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, no. 2, pp. 552–554, retrieved 20 January 2009
- Darwin, Charles (1839), Narrative of the surveying voyages of His Majesty's Ships Adventure and Beagle between the years 1826 and 1836, describing their examination of the southern shores of South America, and the Beagle's circumnavigation of the globe. Journal and remarks. 1832–1836., vol. III, London: Henry Colburn, retrieved 20 January 2009
- Darwin, Charles (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, retrieved 20 January 2009
- Darwin, Charles (1845), Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world, under the Command of Capt. Fitz Roy, R.N. (2 ed.), London: John Murray, retrieved 20 January 2009
- Darwin, Charles (1874), The Structure and Distribution of Coral Reefs (2 ed.), London: Smith Elder and Co, retrieved 20 January 2009
- Darwin, Charles (1887), Darwin, Francis (ed.), The life and letters of Charles Darwin, including an autobiographical chapter, London: John Murray, retrieved 20 January 2009
- Darwin, Charles (1958), Barlow, Nora (ed.), The Autobiography of Charles Darwin 1809–1882. With the original omissions restored. Edited and with appendix and notes by his granddaughter Nora Barlow, London: Collins, retrieved 20 January 2009
- ISBN 0-7181-3430-3
- Davis, W.M. (1920), "The small islands of almost-atolls", Nature, 105 (2636), Nature, v. 105, p. 292–293: 292–293, S2CID 4252726
- Davis, W.M. (1928), The coral reef problem, New York: American Geo¬graphical Society Special Paper No. 9, 596 p.
- FitzRoy, Robert (1839), Voyages of the Adventure and Beagle, Volume II, London: Henry Colburn, retrieved 20 January 2009
- Herbert, Sandra (1991), "Charles Darwin as a prospective geological author", British Journal for the History of Science, vol. 24, no. 2, pp. 159–192, S2CID 143748414, retrieved 20 January 2009
- Herbert, Sandra (2005), Charles Darwin, Geologist, Ithaca, N.Y: Cornell University Press, ISBN 0-8014-4348-2
- Keynes, Richard (2001), Charles Darwin's Beagle Diary, Cambridge University Press, retrieved 20 January 2009
- Lyell, Charles (1830), Principles of Geology, being an attempt to explain the former changes of the Earth's surface, by reference to causes now in operation, vol. 1, London: John Murray, retrieved 20 January 2009
- Rosen, Brian (1982), "Darwin, coral reefs, and global geology", BioScience, vol. 32, no. 6, American Institute of Biological Sciences, Oxford University Press, pp. 519–525, JSTOR 1308903, retrieved 20 January 2009
- van Wyhe, John (27 March 2007), "Mind the gap: Did Darwin avoid publishing his theory for many years?", Notes and Records of the Royal Society, 61 (2): 177–205, S2CID 202574857, retrieved 20 January 2009