Geology Reference
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consider more expansive views of geologic time, like Buffon's. The skeptical reception of
those present spurred him to seek out more evidence to bolster his arguments.
When his lecture was finally published three years later, in 1788, it garnered dismissive
reviews that mischaracterized his unknowably old Earth as a rewarmed version of Aris-
totle's eternal world without beginning or end. Particularly controversial was the conten-
tion that the world evolved in a cyclical fashion. This was totally at odds with the Mo-
saic account in Genesis of the Creation and the Flood. Everyone knew that things hadn't
happened over and over again. The idea that new land was pushed up from beneath the
sea by the force of Earth's internal heat placed Hutton squarely at odds with both Werner's
Neptunist disciples, who believed in an aqueous origin for rocks, and the traditional Chris-
tian conception of a recently created, decaying world.
A simple test of Hutton's idea lay in determining whether granite veins formed along
with or were younger than the rocks they were found in. If precipitated together from
an ancient sea, rocks and the veins they harbored should be the same age. If Hutton was
right—that molten rock rose up from deep below the seafloor—then the veins should cut
across the sedimentary layers.
Scouring the highlands on field excursions, Hutton sought out layered rock cut by veins
of granite. He found what he was looking for in the boulders and exposed bedrock riverbed
of idyllic Glen Tilt, a valley west of Aberdeen. There veins of red granite clearly passed
through bed after bed of black sedimentary rock. The granite had intruded the sedimentary
rock after it was formed. The thin stripes of granite were indeed younger than the rocks in
which they were found.
The following summer, Hutton found more granite veins injected into sedimentary rocks
in Galloway, in southwest Scotland. Even better than at Glen Tilt, these veins terminated
within the exposed strata, only penetrating partway up into the stacked sediments. Not only
was the granite younger, it came from below. Here was more evidence that granite did not
precipitate out of an ancient sea. Hutton felt increasingly confident that what he was seeing
revealed that Earth was far older than anyone believed.
This wasn't enough to prove Hutton's grand cycle. It only validated his mechanism for
uplifting rocks through heat from below. Confident he was right about the larger story, he
kept looking. Three years after he boldly announced that the world was immeasurably old,
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