Geology Reference
In-Depth Information
form. He did not give his own lecture, whether due to illness or a bad case of nerves. His
best friend, Joseph Black, who had recently discovered carbon dioxide, graciously read
it—the tradition being that lectures were written up in advance and simply read aloud at
the meeting. Black presented Hutton's ideas about layered rocks being made of sediment
eroded off of previous land, and how heat and pressure were required to form rocks, as
well as the case for rejecting Werner's ideas about rocks precipitating from an ancient sea.
Ignoring the Bible and the Flood, Hutton had inferred that the world was unknowably old.
Instead of a grand catastrophe to explain the world, he invoked the subtle day-to-day action
of wind, rain, and waves that he himself had observed.
Four weeks later, Hutton personally read a second lecture. He finished his critique of
Werner's theory and focused on how to get stratified layers of rock back to the surface
after they solidified at the base of a thick pile of sediment. If rocks just precipitated from
a shrinking ocean, then they should all lay horizontal. Yet it was well known that some
layered rocks lay steeply inclined. Instead of invoking worldwide collapse during Noah's
Flood to explain the tilted layers (as Steno had), Hutton literally turned the problem on
its head and proposed a different action—Earth's internal heat and volcanic action was
what deformed rocks. The key to his argument was how granite veins cut across layered
rocks. If, as he thought, granite began as molten rock that rises up from the overheated
base of a sedimentary pile, granite veins in cracks and fissures should cut across the lay-
ers in the rocks they pushed up through before cooling. Hutton saw this basic process
as the force driving a grand cycle of regeneration in which the sea and land continually
changed places—continents eroding into oceans to form great piles of sediment that even-
tually melted at the base and rose anew.
Hutton's ability to imagine an endless cycle of erosion and deposition that led to the
formation of fresh rocks kicked open the door for serious consideration of the immensity
of geologic time. He wasn't arguing that the world was older than imagined; he flat-out ar-
gued that Earth was ancient beyond imagination. Who could know how many times rocks
had been recycled? There was no way to know how many cycles of erosion and uplift the
world had seen when each cycle destroyed evidence of prior ones. He must have shocked
an audience that believed Werner's ideas about rocks precipitating out of the ocean on a
not quite six-thousand-year-old world. His extreme views even startled those willing to
