Marie Tharp: The Woman Who Redrew the Earth
One of the great scientific mysteries of the twentieth century was how the Earth’s surface worked. Continents appeared to fit together like pieces of a jigsaw. Mountains rose. Earthquakes and volcanoes followed patterns.
In 1912, the German scientist Alfred Wegener proposed that continents drifted across the Earth’s surface. Most geologists dismissed the idea. He couldn't prove it.
The proof lay beneath the oceans.
Marie Tharp didn’t set out to settle one of science’s great debates. In the 1950s, she was excluded from many research expeditions simply because she was a woman. Instead, she remained on land, analysing thousands of sonar readings collected by survey ships over many years.
To most people, the figures were endless columns of numbers. Tharp saw something different. Patiently plotting each measurement by hand, she began to reveal a hidden landscape of mountains, valleys and deep ocean trenches.
One feature kept appearing.
Running along the crest of the Mid-Atlantic Ridge was a vast rift valley, a giant crack stretching for thousands of miles beneath the sea. It suggested that new ocean floor was continually being created as the seabed slowly pulled apart. Her colleague Bruce Heezen initially dismissed her interpretation because it appeared to support what many geologists regarded as the crackpot theory of continental drift. As more data arrived, however, the pattern became impossible to ignore.
Tharp’s maps became one of the crucial pieces of evidence supporting the emerging theory of seafloor spreading. Together with subsequent discoveries, they helped transform continental drift from a controversial idea into the modern theory of plate tectonics, revealing that the Earth’s crust is made up of enormous moving plates that continually reshape the planet over millions of years.
Today, plate tectonics underpins almost everything we know about the Earth’s history, from the formation of mountain ranges to the distribution of volcanoes and earthquakes.
The Earth had not changed. Marie Tharp had changed humanity’s understanding of it.
Further reading
Soundings: The Story of the Remarkable Woman Who Mapped the Ocean Floor by Hali Felt