Darwin, a naturalist's voyage around the world

STAGE 9

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Le voyage de Darwin

STAGE 9

4 February - 7 September 1835
Chile, earthquake, the Andes, Lima, Gálapagos


On 4 February 1835, the Beagle left the Chiloé Islands and four days later arrived at Valdivia, on the coast of Chile. On February 20, at 11:30 am, a violent earthquake suddenly struck the city. The wooden houses were heavily shaken, the sea level rose as high as the spring tide, and the terrified inhabitants rushed out into the streets. The main earthquake lasted a mere two minutes, but the damage was considerable. In the surrounding area, things were no better. A huge wave had practically wiped the town of Talcahuano off the map, the houses of Concepción were in ruins, the entire coast was littered with beams and furniture, rocks had been smashed to smithereens, land had been uplifted, and above all there were a large number of fatalities.

For Darwin, this was an unhoped-for subject of study. He was able to observe fragments of rock covered with marine growth that had been thrown high up the shore by the earthquake. By comparing this phenomenon with the shells that he had previously observed at high altitudes in the Andes, he became certain of one thing: the mountains were the result of enormous upward motion caused by successive earthquakes of this kind, coupled with extremely slow, imperceptible uplift. When he learnt that volcanoes had started to erupt during the earthquake and that the island of Juan Fernandez situated 576 kilometers away had also been violently shaken, the naturalist also hypothesized that there was an underground connection.

On March 11, the ship dropped anchor at Valparaíso, on the Chilean coast. Darwin took advantage of this to undertake a number of trips into the Andes. The rarefied air and the icy winds made it hard to climb these peaks covered with eternal snows. But Darwin quickly forgot the altitude sickness when he discovered fossilized shells at high altitude, new evidence of the marine origins of the Andes. There was even more convincing evidence: the presence of the remains of submarine lava at an altitude of over 2000 meters! He was also surprised by the difference in flora and fauna between the Pacific and Atlantic sides of the mountain range. It appeared that this impassable natural barrier had led to the development of very different species on either side of the range.

On April 27, Darwin set out on a second series of trips to the North, leaving the picturesque city of Valparaíso, to which he was not to return. The region abounded in gold, silver and copper, dug out by the Chilean miners, whose lives were little better than those of beasts of burden. When out studying the geology, Darwin was sometimes suspected of being a prospector! The countryside became increasingly arid, with deserts that were for the most part barren. The few trees and shrubs of central Chile became increasingly scarce, gradually giving way to very large plants related to the yucca, while the large "chandelier-like" cacti were replaced by smaller versions. As for animals, the quadrupeds of the region appeared to consist mostly of guanacos and foxes. In these difficult conditions, getting hold of fresh water, wood and fodder for the horses was a daily challenge!

In early July, Darwin met up with the Beagle again at the foot of the Copiapo valley. On the 12th, the crew dropped anchor in the poverty-stricken port of Iquique, and Darwin visited a saltpeter mine in the desolate surroundings. A week later, the ship arrived in Callao, the port of Lima, the capital of Peru. A revolution had broken out in the country, and complete political anarchy reigned, with no less than four political parties in arms fighting for power. In this context, journeys inland were impossible, preventing the naturalist from exploring the region. So Darwin changed tack. He sent a batch of specimens back to England, and then visited the city and its immediate surroundings. Here he came across the ruins of an ancient Indian village. The remains of houses, burial mounds, irrigation works, pottery, fabrics, jewelry and tools were evidence of an advanced civilization, and aroused his admiration.

On September 7, the Beagle set off from the port of Callao, heading due west towards the Galápagos Islands. Darwin didn't know it yet, but the next stage in the journey was to be decisive for the future development of his theory of natural selection. But for now, he was simply excited at the thought of discovering these fascinating Pacific islands!

CNRS    sagascience