Erosion of the Earth
Year of Discovery: 1792
What Is It? The earth’s surface is shaped by giant forces that steadily, slowly
act to build it up and wear it down.
Who Discovered It? James Hutton
Why Is This One of the 100 Greatest?
In the eighteenth century scientists still believed that Earth’s surface had remained unchanged until cataclysmic events (the great flood of Noah’s ark fame was the most often
sited example) radically and suddenly changed the face of our planet. They tried to understand the planet’s surface structures by searching for those few explosive events. Attempts
to study the earth, its history, its landforms, and its age based on this belief led to wildly inaccurate guesses and misinformation .
James Hutton discovered that the earth’s surface continually and slowly changes,
evolves. He discovered the processes that gradually built up and wore down the earth’s surface. This discovery provided the key to understanding our planet’s history and launched
the modern study of earth sciences.
How Was It Discovered?
In the 1780s, 57-year-old, more-or-less retired physician and farmer (and amateur geologist) James Hutton decided to try to improve on the wild guesses about the age of the earth that
had been put forth by other scientists. Hutton decided to study the rocks of his native Scotland
and see if he could glean a better sense of Earth’s age by studying the earth’s rocks.
Lanky Hutton walked with long pendulum-like strides across steep, rolling green hills.
Soon he realized that the existing geological theory—called catastrophism—couldn’t possibly be right. Catastrophism claimed that all of the changes in the earth’s surface were the result of sudden, violent (catastrophic) changes. (Great floods carved out valleys in hours. Great
wrenchings shoved up mountains overnight.) Hutton realized that no catastrophic event could
explain the rolling hills and meandering river valleys he hiked across and studied.
It was one thing to say that an existing popular theory was wrong. But it was quite another to prove that it was wrong or to suggest a replacement theory that better explained
Earth’s actual surface. Hutton’s search broadened as he struggled to discover what forces
actually formed the hills, mountains, valleys, and plains of Earth.
Late that summer Hutton stopped at a small stream tumbling out of a steep canyon.
Without thinking, he bent down and picked up a handful of tiny pebbles and sand from the
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