Continental Drift
Year of Discovery: 1915
What Is It? Earth’s continents drift and move over time.
Who Discovered It? Alfred Wegener
Why Is This One of the 100 Greatest?
Before Wegener’s discovery, scientists thought that the earth was a static body—never
changing, now as it always has been. Alfred Wegener’s discovery that Earth’s continents
drift across the face of the planet led to modern tectonic plate theories and to a true understanding of how Earth’s crust, mantel, and core move, flow, and interact. It created the first
sense of Earth’s dynamic history.
Wegener’s discovery solved nagging mysteries in a dozen fields of study—and stirred
up new questions still being debated today. This discovery stands as a cornerstone of our
modern understanding of earth sciences.
How Was It Discovered?
Albert Wegener was born in 1880 in Berlin. Always restless and more of a doer than a
thinker, he switched his college major from astronomy to meteorology because “astronomy
offered no opportunity for physical activity.” Upon graduation, Wegener signed on for meteorological expeditions to Iceland and Greenland in 1906 and 1908.
While on tour in 1910, Wegener noticed the remarkable fit of the coastlines of South
America and Africa. He was not the first scientist to notice this fit, but one of the first to
think that it was important.
In 1911, new ocean maps showed the Atlantic Ocean continental shelves. (Continental
shelves are shallow, underwater shelves extending out from continents.) Wegener noticed
an even better fit between the continental shelves of South America and Africa. They “fit
like pieces of a jigsaw puzzle.”
Wegener knew that this perfect fit couldn’t be just a coincidence and suspected that
those two continents were once connected—even though they were now separated by several thousand miles of ocean. This was a radical notion since all scientists assumed that the
continents never moved from their fixed positions on Earth.
In that same year, Wegener read studies that noted the same fossil finds in South
America and in corresponding parts of coastal Africa. Many scientists proposed that there
once existed a land bridge between the two so that plant and animal species could intermix.
This bridge, they assumed, long ago sank to the bottom of the sea.
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