The Universe Within (16 page)

Wegener proposed that the different
continents were originally connected as one huge supercontinent in the distant past. Over time, the continents drifted apart, forming the configurations of the oceans and coastlines we see today. The first split would have been between a
northern chunk and a
southern one. This southern one contained what is today
Africa,
South America,
Australia,
India, and
Antarctica.

This simple idea answers many questions. Why the special similarity of the
plants from the southern continents? Because they were originally part of the same landmass, after the supercontinent broke into chunks. Why
glaciers at the equator in India? Because India wasn’t always at the equator; it drifted over time from a position closer to the poles. And why the jigsaw shape of the continents? Because they all fit together at some point millions of years ago.

What about the response to this grand unifying concept of Wegener’s? Familiar with
Glossopteris
and the geological similarities among Africa, India, and South America, geologists working in southern continents and
Europe tended to view the idea favorably. The reception in
North America was something else altogether. The comments of one of my predecessors here at the
University of Chicago, in 1920, summarizes the state of affairs: “Wegener’s hypothesis in general is of the footloose type, in that
it takes considerable liberty with our globe, and is less bound by restrictions or tied down by awkward, ugly facts than most of its rival theories.”

Wegener’s critics agreed that the coastlines might have looked like matching jigsaw pieces, but to them the similarity was more coincidence than reality. They could envision no engine that could move the continents. Did the landmasses roar through the ocean crust like icebreakers through pack ice, crunching and crushing miles of rock along the way? Nothing in science spoke to this. In fact, everything we knew of the
seafloor at the time spoke to the opposite: the bottom of the ocean appeared to be one of the calmest and most featureless places on Earth.

Of course, most of the planet was a total mystery in the early part of the twentieth century. Close to 70 percent of Earth is covered by ocean, and in Wegener’s day we knew more of the bright surface of the moon than of Earth.

December 7, 1941, the day of infamy at Pearl Harbor, had a major impact on our understanding of the planet.
Harry Hess, a young geologist at
Princeton, was called to war and, being a naval reservist, shipped out from Princeton to New York City to report for active duty on December 8. When he arrived at the headquarters on Church Street, he was asked if he “knew about latitude and longitude.” Little did Hess’s recruiters realize that years before he had been at sea on expeditions to explore and map features of the
ocean floor. Hess’s answer to the question was likely satisfactory, as he rose to become navigation and executive officer on the
USS
Cape Johnson
, a maritime freighter converted into a troop transport. The
Cape Johnson
went to the
South Pacific and served during battles at Guam and Iwo Jima. Hess, ever the geologist, had an additional mission in mind during these battles.

On board the
Cape Johnson
was a device known as a
Fathometer, a simple kind of sonar that measures the depth of the ocean. Modern versions of these devices are small enough to carry on a canoe—think Fishfinder—but during World War II these were the size of a small refrigerator and were towed behind the boat. Hess found a painless way to do science during wartime: just leave the Fathometer running while the
Cape Johnson
performed its military duties.

This effort didn’t cost Uncle Sam much, but it had a large impact on Hess’s thinking. Hess found a number of small flat-topped mountains on the seafloor. These little submarine mesas were to have a major impact on science fifteen years after the war—insights that were kindled when he heard of the work of another person whose life’s trajectory was changed by Pearl Harbor.

Marie Tharp had no inkling of a career in geology when she matriculated at Ohio University in Athens in the late 1930s. Her path was toward a “proper” woman’s career at the time: nursing or teaching. Nothing clicked. Scared of blood, she left nursing to take courses in education. That curriculum didn’t excite her either. Her opportunity came after the call-up on December 7, when millions of men were pulled from their jobs to fight the Axis powers. The Department of Geology at Michigan broke with long tradition and offered new opportunities for female students to study. The geology scholarship seemed as good a gig as any, so off Tharp went to study Earth.

By the late 1940s, with her earth science degree in hand, Tharp had gone to New York City to find a job. Her first stop,
in the paleontology department at the
American Museum of Natural History, was not promising. When she inquired about a position preparing
fossils for research and display, her blood ran cold when a paleontologist told her that it took up to two years to discover and remove fossils inside rocks. Tharp later said that she “couldn’t imagine devoting so much time to something like that.” Paleontology’s loss was geology’s gain. Tharp went to
Columbia University to meet the head of a major geological team there,
Maurice “Doc” Ewing.

Doc Ewing was a big Texan who was leading an effort to map the seas. In the shift from
World War II to the
Cold War, one thing remained constant: submariners needed to know about the structure of the ocean floor. The
Office of Naval Research filled the demand by funding expeditions worldwide to look at the ocean’s depth and structure. Ewing was sending boats throughout the year to collect
cores, depth readings, and other information from the ocean bottoms. With so much data coming in, he required someone to compile and map them. Tharp was hired first; later Ewing recruited an Iowan named
Bruce Heezen to direct her and the mapping effort. Heezen swiftly rose through the ranks to become a professor at Columbia, while Tharp remained as his assistant.

These were heady days in geology. Each month, Doc Ewing’s boats returned with reams of new data from completely unexplored regions of our own world. Tharp and Heezen were in the middle of this frenzy, synthesizing much of the data Ewing’s teams collected. The two worked hard and became very close, but in a way nobody could entirely comprehend. Heezen, a married man, often entertained students and colleagues at Tharp’s house near the laboratory. Some days they would battle, with Heezen throwing Tharp’s drawings in the trash or screaming insults that shattered the normal quiet of the halls. Other times, the two would behave as a team, defending each other during vicious political battles that were part of the environment of the
lab. Always close, Tharp and Heezen had a relationship that was, by all accounts, emotionally intense but entirely platonic.

One day, after countless hours compiling shipborne records of the ocean depth, Tharp saw a linear chain of mountains over a mile high that extended along the floor of the
Atlantic Ocean. There were solid hints before that these ridges existed, but she followed them as they coursed forty thousand miles on the bottom of the ocean, through virtually every ocean on the globe. Then she looked at the structure of the ridges themselves. Within the apex of each ridge sat what looked like a giant valley—a depression that split the ridge in two. The walls on either side of this valley appeared to match up. Tharp had a hunch what this implied: Earth was opening up at the ridges as it rifted apart at the bottom of the ocean. To her, this was evidence that the
seafloor was expanding. Excited, she approached Heezen with the idea.

Heezen hated Tharp’s discovery, calling it “girl talk.” Like Tharp, he saw the implication immediately. To him, Tharp’s rift in the center of the seafloor looked “too much like continental drift.” If the middles of the
oceans were separating, then the continents were moving apart, and
Wegener would be right after all. Heezen couldn’t abide this speculation.