Travel Reference
In-Depth Information
The
Beagle
was exploring a world of astonishing geological activity, far
more obvious in its ef ects than the processes that had shaped the English
countryside with which Darwin was familiar. Indeed, just before embarking
on the voyage, Darwin had taken a fi eld trip to Wales with Cambridge's geol-
ogy professor Adam Sedgwick. Both of them—as Darwin later admitted—
had totally missed the signs of the glaciers that had carved and shaped the
Welsh valleys.
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But nobody could miss the geological processes at work in Tierra del
Fuego and the tip of Chile. When Darwin arrived at the bay of San Carlos in
southern Chile in January 1835, he had already seen the dramatic ef ects of
glaciers in shaping Chile's southern tip. Now he watched in wonder as the
nearby volcano Osorno hurled fi reballs into the sky. Later he learned that
two other giant volcanoes, spaced along South America's western coast over
a span of 4,000 kilometers, had been in full eruption at the same time.
As the
Beagle
sailed northward along South America's west coast, it was
almost always within sight of the Andes, the world's second highest mountain
range and one of its youngest. Darwin was aware of the argument between
catastrophist and uniformitarian geologists over how such immense moun-
tains had been built. Catastrophists assumed that such immense features had
been produced by a single event such as Noah's fl ood, or by a series of catas-
trophes that marked periods of great upheaval in the Earth's history. But
Darwin favored the theory of the geologist Charles Lyell, who built on ear-
lier ideas of James Hutton and proposed that the Earth's geological features
can be explained by the processes we see around us. Mountains, Lyell main-
tained, are built up gradually through volcanic activity and earthquakes, and
broken down equally slowly through erosion. He called his theory of gradual
change uniformitarianism. Darwin, confronted by mountains larger than he
had ever seen, was determined to test Lyell's hypothesis.
In order to explain the slow formation of such immense geological fea-
tures as the Andes, Lyell's uniformitarian theory postulated that the Earth
was ancient, and that spans of time in the order of hundreds of millions of
years must have passed. When Darwin later formulated his theory of evo-
lution, he too made the assumption that the world has existed for great
stretches of time. This would, he postulated, have given sui cient time for
