South America Split 20 Million Years Ago
the late 18th century Benjamin Franklin hypothesized
that Africa [right] and South America [left] were once
joined. We now know that he was right. Approximately
20 million years ago these two continents were one.
Then a giant rift, or separation, developed between
them. As the two land masses separated, the surrounding
water rushed in to fill the gap between them, and the
Atlantic Ocean was born. They've been drifting apart
about 5 centimeters per year - for the past 20 million
years!-as the Atlantic continues to widen.
What began as a small crack in the Earth's crust is
now the Mid-Atlantic Ridge, a giant undersea mountain
range. As magma rises to escape along this ridge new
crust is formed, sea-floors spread, and continents
drift around the globe.
Thanks to Bruce Heezen and Marie Tharpe.