Uniformitarianism: Charles Lyell (2 of 3)

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Gradual Change
For inspiration, Lyell turned to the fifty-year-old ideas of a Scottish farmer named James Hutton. In the 1790s, Hutton had argued that the Earth was transformed not by unimaginable catastrophes but by imperceptibly slow changes, many of which we can see around us today. Rain erodes mountains, while molten rock pushes up to create new ones. The eroded sediments form into layers of rock, which can later be lifted above sea level, tilted by the force of the uprising rock, and eroded away again. These changes are tiny, but with enough time they could produce vast changes. Hutton therefore argued that the Earth was vastly old—a sort of perpetual-motion machine passing through regular cycles of destruction and rebuilding that made the planet suitable for mankind.

Lyell traveled through Europe to find more evidence that gradual changes, the same we can see happening today, had produced the features of the Earth’s surface. He found evidence for many rises and falls of sea level, and of giant volcanoes built on top of far older rocks. Processes such as earthquakes and eruptions, which had been witnessed by humans, were enough to produce mountain ranges. Valleys were not the work of giant floods but the slow grinding force of wind and water.

Uniform Processes of Change
Lyell’s version of geology came to be known as uniformitarianism, because of his fierce insistence that the processes that alter the Earth are uniform through time. Like Hutton, Lyell viewed the history of Earth as being vast and directionless. And the history of life was no different.

• Valley image courtesy of David Smith, UCMP.