The Galápagos Islands (official name: Archipiélago de Colón, other Spanish name: Islas Galápagos) are an archipelago of volcanic islands distributed on either side of the Equator in the Pacific Ocean surrounding the centre of the Western Hemisphere, 906 km (563 mi) west of continental Ecuador, of which they are a part. The islands are known for their vast number of endemic species and were studied by Charles Darwin during the voyage of the Beagle, as his observations and collections contributed to the inception of Darwin’s theory of evolution by natural selection.
The islands are located in the eastern Pacific Ocean, 973 km (605 mi) off the west coast of South America. The closest land mass is that of mainland Ecuador, the country to which they belong, 926 km/500 nmi to the east. The voyage of the Beagle brought the survey ship HMS Beagle, under captain Robert FitzRoy, to the Galápagos on 15 September 1835 to survey approaches to harbours. The captain and others on board, including his companion, the young naturalist Charles Darwin, made observations on the geology and biology on Chatham, Charles, Albemarle and James islands before they left on 20 October to continue on their round-the-world expedition.
Primarily a geologist at the time, Darwin was impressed by the quantity of volcanic craters they saw, later referring to the archipelago as “that land of craters“. His study of several volcanic formations over the 5 weeks he stayed in the islands, led to several important geological discoveries, including the first, correct explanation for how volcanic tuff is formed. Darwin noticed the mockingbirds differed between islands, though he thought the birds now known as Darwin’s finches were unrelated to each other, and did not bother labelling them by island. Nicholas Lawson, acting Governor of Galápagos for the Republic of the Equator, met them on Charles Island, and as they walked to the prison colony, Lawson told Darwin the tortoises differed from island to island.
Towards the end of the voyage, Darwin speculated that the distribution of the mockingbirds and the tortoises might “undermine the stability of Species”. When specimens of birds were analysed on his return to England, it was found that many apparently different kinds of birds were species of finches, which were unique to islands. These facts were crucial in Darwin’s development of his theory of natural selection explaining evolution, which was presented in The Origin of Species.