Principles of Geology wasn’t simply a rehash of Hutton’s ideas. Lyell offered a much richer, scientifically detailed vision of how the changes humans witness could have gradually shaped the planet. He offered evidence of volcanic eruptions building islands, of earthquakes having lifted land; he then showed how erosion could grind these exposed features down again. Geological change was happening slowly, imperceptibly, Lyell argued, even over the course of human history. The frontispiece of Principles shows the ancient Roman temple of Serapis, with dark bands marking the tops of its pillars, caused by mollusks that at some point had drilled into them. Within the lifetime of the temple it had been completely submerged and then raised from the ocean again. Unlike Hutton, Lyell didn’t see Earth going through a grand, global cycle of creation and destruction. The planet changed locally, eroding here, erupting there, in a state of perpetual, directionless flux for an unimaginable span of time.
Darwin was fascinated by Principles of Geology. He realized that it offered not only a compelling vision of Earth’s history but a method for testing it against the real world. When he landed at Saint Jago he had an opportunity to do just that. He scrambled over the volcanic rock of the island and found clues that the lava had originally poured out underwater, baking coral and shells as it spread. Subterranean forces must have later lifted the rock up to the sea’s surface, but they must have then lowered it back down and lifted it up yet again. Some of the rising and falling must have happened only recently, Darwin realized, for in a band of rock in the cliffs he could find fossils of shells that matched those of creatures still alive around the island. Earth was changing in 1832, as it had for eons.
Darwin would write in his autobiography, “The very first place which I examined, namely St. Jago in the Cape de Verde islands, showed me clearly the wonderful superiority of Lyell’s manner of treating geology, compared with that of any other author, whose works I had with me or even afterwards read.”
He had tried out Lyell’s methods and they had worked beautifully. Darwin became a Lyellian on the spot.
At the end of February 1832 the Beagle reached South America. FitzRoy kept the ship in Rio de Janeiro for three months, and then sailed south. Although the Beagle would travel along the coast of South America for the next three years, Darwin spent most of that time on land. In Brazil, he lived in a cottage in the jungle, overwhelmed by the biological Eden that surrounded him. In Patagonia, he rode horseback through the interior for weeks at a time, always managing to get back to the Beagle in time for the next leg of the voyage. He recorded everything he encountered, the fireflies, the mountains, the slaves, and the cowboys. His empty specimen jars began to fill with hundreds of strange new creatures.
On one excursion near Punta Alta on the coast of Argentina, Darwin inspected low cliffs and discovered bones. Prying them out of the gravel and quartz, he found that they were enormous teeth and thigh bones belonging to gigantic extinct mammals. He came back over the course of the next few days and dug out more. At that time, there was only a single fossil of an extinct mammal in all the collections of England, but at Punta Alta Darwin uncovered tons of bones. He didn’t know quite what to make of them, guessing that they were giant rhinos and sloths. But Darwin was still just a collector at this point. He simply packed up the fossils and had them sent home.
There was a puzzle to these fossils, the first of many that Darwin would encounter on his voyage. As a good student of Cuvier, Darwin assumed that these were antediluvian monsters, long extinct. But their bones were mixed in with the fossils of shells that were almost identical to those of living species on the Argentine coast. The rocks were hinting that the monsters were not as ancient as they might seem.
The Beagle rounded Tierra del Fuego in December 1832. This was supposed to be the highlight of the trip for FitzRoy, as he returned his captured Indians to their tribes, bringing with them the powers of civilization. But Tierra del Fuego defeated him again. FitzRoy tried to set up a mission at Wollya Bay, building three wigwams and two gardens. He equipped the mission with the donations of kindly but oblivious London ladies: wineglasses, tea trays, soup tureens, and fine white linens. A few weeks later, when the Beagle checked in again at Wollya Bay, the missionary came running to the ship, screaming for his life. The Fuegans had stolen or destroyed everything, and at the ship’s return they were amusing themselves by plucking his beard hairs with mussel shells.
FitzRoy gloomily sailed the Beagle around Cape Horn and headed for the west coast of South America. Darwin took the opportunity to climb the Andes Mountains. Thinking of Lyell, he tried to picture their tall peaks rising out of the ocean. He rejoined the Beagle as it traveled north from Valparaiso, with Mount Osorno looming over them to the east, its peak a perfect cone. As the sailors worked their instruments in the rain, they would stop sometimes to watch clouds of smoke rise from its top. One night in January Osorno exploded, launching boulders and flame. Not even Lyell himself had seen a volcano erupt.
Earth was not finished with its violence, though. The Beagle anchored at the town of Valdivia a few weeks later, and on February 20,1835, the planet danced under Darwin. He had been taking a forest walk near town and had decided to rest. When he lay down, the earth felt as hard and unyielding under him as it ever had, utterly imperturbable. And then it shivered.
“It came on suddenly and lasted two minutes; but the time appeared much longer,” Darwin wrote later. Having spent his life in the geological tranquility of England, he had never experienced an earthquake before. “There was no difficulty in standing upright, but the motion made me almost giddy. It was something like the movement of a vessel in a little cross ripple, or still more like that felt by a person skating over thin ice, which bends under the weight of his body.”
The trees swayed in the breeze, and the quake stopped. Darwin would not forget the experience. “A bad earthquake at once destroys the oldest associations: the world, the very emblem of all that is solid, has moved beneath our feet like a crust over a fluid; one second of time has conveyed to the mind a strange idea of insecurity, which hours of reflection would never have created.”
After the earthquake was over, Darwin hurried back to the town, which he found relatively unharmed. But farther up the coast, the city of Concepción had collapsed into a heap of bricks and timbers. It had been hit by the quake, and by a tidal wave that the quake had triggered. The front of the city’s cathedral was sheared off the building as if with a chisel. “It is a bitter 8c humiliating thing,” Darwin wrote in his diary, “to see works which have cost men so much time & labor overthrown in one minute.” Cracks had opened in the ground, rocks had shattered. In two minutes, the earthquake had done more damage, Darwin guessed, than a century of ordinary wear and tear.
The earthquake had done something even more profound to the coast, something that was more difficult to appreciate than all the ruined buildings and drowned cattle. Stretches of land that had once been underwater were now up out of the water, covered with dying shellfish. FitzRoy discovered with his surveying instruments that parts of the coast had risen 8 feet during the earthquake. Two months later he returned to Concepción and found that the ground was still elevated.
Darwin realized that Lyell had provided him with the explanation for what he was witnessing. The pressure of molten rock must have triggered the eruption at Osorno and then had enough strength to trigger the earthquake. The injection of fresh molten rock had raised new land out of the ocean. With enough time, it could eventually lift entire mountain ranges into the sky.